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NATUKAL SELECTION

AND

TEOPICAL NATUEE

NATUEAL SELECTION

TEOPICAL NATUEE

DESCRIPTIVE AND THEORETICAL BIOLOGY

BY

ALFEED EUSSEL WALLACE

AUTHOR OF 'THE MALAY ARCHIPELAGO,' 'ISLAND LIFE,' 'DARWINISM,
ETC.

NEW EDITION WITH CORRECTIONS AND ADDITIONS

MACMILLAN AND CO.

AND NEW YORK
1891

All rights reserved

NATURAL SELECTION. First Edition 1870.
Reprinted 1875.

TROPICAL NATURE. First Edition 1878.

PEEFACE

THE present volume consists mainly of a reprint of two
volumes of essays — Contributions to the Theory of Natural
Selection, which appeared in 1870, with a second edition in
1871, and has now been many years out of print; and,
Tropical Nature and Other Essays, which appeared in 1878.

In preparing a new edition of these works to appear as
a single volume I have thought it advisable to omit two
essays — that on "The Malayan Papilionidae " as being too
technical for general readers, and that on " The Distribution
of Animals as indicating Geographical Changes," which con-
tains nothing that is not more fully treated in my other
works. Another essay — "By - Paths in the Domain of
Biology" — has also been partly omitted, one portion of it
forming a short chapter on " The Antiquity and Origin of
Man," while another portion has been incorporated in the
chapter on " The Colours of Animals and Sexual Selection."
More than compensating for these omissions are two new
chapters — " The Antiquity of Man in North America " and
"The Debt of Science to Darwin."

Many corrections and some important additions have been
made to the text, the chief of which are indicated in the
table given below ; and to facilitate reference the two original
works have separate headings, and form Parts I. and II. of
the present volume.

PREFACE

ALTERATIONS IN THE SECOND EDITION OF.
CONTRIBUTIONS, ETC.

IST ED.

»»

PRESENT
VOLUME.

221

221

Additional facts as to birds acquiring the

223

223A\

song of other species ....
Mr. Spruce's remarks on young birds

105

228

223B/
228A1

pairing with old ....
Pouchet's observations on a change in

107

228B/

the nests of swallows ....

omitted

229

Passage omitted about nest of Golden

Crested Warbler, which had been in-

serted on Rennie's authority, but has

not been confirmed by any later ob-

servers.

261

261

Daines Barrington, on importance of pro-
tection to the female bird .

138

372

Note A

205

372B

Note B . . . .

209

ADDITIONAL MATTER IN THE PRESENT VOLUME.
NATURAL SELECTION.

PAGES

Additional facts by Leroy, Spalding, Lowne, and Dixon on the

Nest-Building and other Instincts of Birds . . . 108-112

Dr. Abbott on Nesting of Baltimore Oriole . . .114

Professor Jeitteles and Mr. Henry Reeks on Alterations in Mode
of Nest-Building . . . . . .115

TROPICAL NATTTRE.

Note on Dr. Shufeldt's Investigations into the Affinities of
Swifts and Hmnming-Birds . . . . .337

THE ANTIQUITY OF MAN IN NORTH AMERICA.
(Additional Chapter) ...... 433-449

THE DEBT OF SCIENCE TO DARWIN.
(Additional Chapter) ... . 450-475

PARKSTONE, DORSET,
March 1891.

CONTENTS

NATURAL SELECTION

I. ON THE LAW WHICH HAS REGULATED THE INTRODUCTION OF

NEW SPECIES

Geographical Distribution dependent on Geologic Changes— A Law deduced
from well-known Geographical and Geological facts — The Form of a
true system of Classification determined by this Law — Geographical
Distribution of Organisms— Geological Distribution of the Forms of
Life — High Organisation of very ancient Animals consistent with
this Law — Objections to Forbes's Theory of Polarity — Rudimentary
Organs— Conclusion . . . . Pages 3-19

II. ON THE TENDENCY OF VARIETIES TO DEPART INDEFINITELY

FROM THE ORIGINAL TYPE

Introductory Note — Instability of Varieties supposed to prove the per-
manent distinctness of Species — The Struggle for Existence — The
Law of Population of Species — The Abundance or Rarity of a Species
dependent upon its more or less perfect Adaptation to the Conditions
of Existence — Useful Variations will tend to Increase ; useless or
hurtful Variations to Diminish — Superior Varieties will ultimately
Extirpate the Original Species — The Partial Reversion of Domesti-
cated Varieties explained — Lamarck's Hypothesis very different
from that now advanced — Conclusion .... 20-33

III. MIMICRY, AND OTHER PROTECTIVE RESEMBLANCES AMONG

ANIMALS

Test of true and false Theories— Importance of the Principle of Utility
— Popular Theories of Colour in Animals — Importance of Conceal-
ment as Influencing Colour — Special Modifications of Colour — Theory

CONTENTS

of Protective Colouring — Objection that Colour, as being dangerous,
should not exist in Nature — Mimicry — Mimicry among Lepidoptera
— Lepidoptera mimicking other Insects — Mimicry among Beetles —
Beetles mimicking other Insects— Insects mimicking Species of other
Orders — Cases of Mimicry among the Vertebrata — Mimicry among
Snakes — Mimicry among Birds — Mimicry among Mammals — Objec-
tions to Mr. Bates's Theory of Mimicry — Mimicry by Female Insects
only — Cause of the dull Colours of Female Birds — Use of the gaudy
Colours of many Caterpillars — Summary — General deductions as to
Colour in Nature — Conclusion . . . . Pages 34-90

IV. ON INSTINCT IN MAN AND ANIMALS

How Instinct may be best Studied — Definition of Instinct — Does Man
possess Instincts ? — How Indians travel through unknown and track-
less Forests 91-97

V. THE PHILOSOPHY OP BIRDS' NESTS

Instinct or Keason in the Construction of Birds' Nests — Do Men build by
Reason or by Imitation ? — "Why does each Bird build a peculiar kind
of Nest ? — How do young Birds learn to build their first Nest ?
Do Birds sing by Instinct or by Imitation ? — How young Birds may
learn to build Nests— The Skill exhibited in Nest-building Ex-
aggerated— Man's Works mainly Imitative — Birds do Alter and
Improve their Nests when altered Conditions require it — Conclusion

98-117

VI. A THEORY OP BIRDS' NESTS

Changed Conditions and persistent Habits as influencing Nidification—
Classification of Nests — Sexual differences of Colour in Birds — The
Law which connects the Colours of Female Birds with the mode of
Nidification — What the Facts Teach us — Colour more variable than
Structure or Habits, and therefore the Character which has generally
been Modified — Exceptional cases confirmatory of the above Explana-
tion—Real or apparent exceptions to the Law stated at page 124—
Various modes of Protection of Animals — Females of some groups
require and obtain more Protection than the Males — Conclusion

118-140

VII. CREATION BY LAW

Laws from which the Origin of Species may be deduced — Mr. Darwin's
Metaphors liable to Misconception — A case of Orchid-structure ex-

CONTENTS

plained by Natural Selection — Adaptation brought about by General
Laws — Beauty in Nature — How New Forms are produced by Varia-
tion and Selection— The Objection that there are Limits to Variation
— Objection to the Argument from Classification — The Times on
Natural Selection — Intermediate or generalised Forms of Extinct
Animals an indication of Transmutation or Development— Conclu-
sion—A Demonstration of the Origin of Species by Natural Selection

Pages 141-166

VIII. THE DEVELOPMENT OF HUMAN KACES UNDER THE LAW
OF NATURAL SELECTION

"Wide differences of Opinion as to Man's Origin— Outline of the Theory
of Natural Selection — Different Effects of Natural Selection on
Animals and on Man — Influence of External Nature in the develop-
ment of the Human Mind — Extinction of Lower Races — The Origin
of the Races of Man — The Bearing of these Views on the Antiquity
of Man — Their Bearing on the Dignity and Supremacy of Man —
Their Bearing on the future Development of Man — Summary — Con-
clusion 167-185

IX. THE LIMITS OF NATURAL SELECTION AS APPLIED TO MAN

What Natural Selection can Not do — The Brain of the Savage shown
to be Larger than he Needs it to be — Size of Brain an important
Element of Mental Power — Comparison of the Brains of Man and of
Anthropoid Apes — Range of Intellectual Power in Man — Intellect of
Savages and of Animals compared — The use of the Hairy Covering
of Mammalia — The Constant Absence of Hair from certain parts of
Man's body a remarkable Phenomenon — Savage Man feels the want
of this Hairy Covering— Man's Naked Skin could not have been pro-
duced by Natural Selection — Feet and Hands of Man considered as
Difficulties on the Theory of Natural Selection— The Voice of Man—
— The Origin of some of Man's Mental Faculties, by the preservation
of Useful Variations, not possible — Difficulty as to the Origin of the
Moral Sense — Summary of the Argument as to the Insufficiency of
Natural Selection to account for the Development of Man — The
Origin of Consciousness — The Nature of Matter — Matter is Force
—All Force is probably Will-force— Conclusion . . 186-214

CONTENTS

TEOPICAL NATURE AND OTHER ESSAYS

I. THE CLIMATE AND PHYSICAL ASPECTS OF THE EQUATORIAL

ZONE

The three Climatal Zones of the Earth — Temperature of the Equatorial
Zone — Causes of the Uniform High Temperature near the Equator —
Influence of the Heat of the Soil — Influence of the Aqueous Vapour
of the Atmosphere — Influence of Winds on the Temperature of the
Equator — Heat due to the Condensation of Atmospheric Vapour —
General Features of the Equatorial Climate — Uniformity of the
Equatorial Climate in all Parts of the Globe— Effects of Vegetation
on Climate— Short Twilight of the Equatorial Zone— The Aspect of
the Equatorial Heavens — Intensity of Meteorological Phenomena at
the Equator — Concluding Remarks . . Pages 217-237

II. EQUATORIAL VEGETATION

The Equatorial Forest-belt and its Causes— General Features of the Equa-
torial Forests— Characteristics of the Larger Forest-Trees—Flowering
Trunks and their Probable Cause — Uses of Equatorial Forest-trees —
The Climbing Plants of the Equatorial Forests— Palms— Uses of Palm-
trees and their Products — Ferns — Ginger-worts and Wild Bananas —
Arums— Screw- pines— Orchids— Bamboos— Uses of the Bamboo— Man-
groves—Sensitive Plants— Comparative Scarcity of Flowers— Con-
cluding Remarks on Tropical Vegetation . . . 238-269

III. ANIMAL LIFE IN THE TROPICAL FORESTS

Difficulties of the Subject— General Aspect of the Animal Life of Equa-
torial Forests— Diurnal Lepidoptera or Butterflies— Peculiar Habits of
Tropical Butterflies— Ants, Wasps, and Bees— Ants— Special Rela-
tions between Ants and Vegetation— Wasps and Bees— Orthoptera
and other Insects— Beetles— Wingless Insects— General Observations
on Tropical Insects— Birds— Parrots— Pigeons— Picarise— Cuckoos—
Trogons, Barbets, Toucans, and Hornbills— Passeres— Reptiles and
Amphibia : Lizards— Snakes— Frogs and Toads— Mammalia : Mon-
keys—Bats—Summary of the Aspects of Animal Life in the Tropics

270-311

CONTENTS

IV. HUMMING-BIRDS : As ILLUSTRATING THE LUXURIANCE OP
TROPICAL NATURE

Structure— Colours and Ornaments— Descriptive Names— The Motions and
Habits of Humming-birds — Display of Ornaments by the Male — Food
— Nests — Geographical Distribution and Variation — Humming-birds
of Juan Fernandez as illustrating Variation and Natural Selection —
The Eolations and Affinities of Humming-birds — How to Determine
Doubtful Affinities — Resemblances of Swifts and Humming-birds —
Differences between Sun-birds and Humming-birds — Conclusion

Pages 312-337

V. THE COLOURS OF ANIMALS AND SEXUAL SELECTION

General Phenomena of Colour in the Organic World — Theory of Heat and
Light as producing Colour — Changes of Colour in Animals produced
by Coloured Light — Classification of Organic Colours — Protective
Colours — Warning Colours — Sexual Colours — Normal Colours — The
Nature of Colour — How Animal Colours are produced — Colour a
Normal Product of Organisation — Theory of Protective Colours —
Theory of Warning Colours — Imitative Warning. Colours — The Theory
of Mimicry — Theory of Sexual Colours — Colour as a means of
Recognition — Colour proportionate to Integumentary Development —
Selection by Females not a cause of Colour — Probable use of the
Horns of Beetles — Cause of the greater Brilliancy of some Female
Insects — Origin of the Ornamental Plumage of Male Birds —
Theory of the Display of Ornaments by Males — Natural Selection
as neutralising Sexual Selection — Greater Brilliancy of some Female
Birds — Colour - development as illustrated by Humming-birds —
— Theory of Normal Colours — Local causes of Colour-development —
The influence of Locality on Colour in Butterflies and birds — Sense -
perception influenced by Colour of the Integuments — Summary on
Colour-development in Animals .... 338-394

VI. THE COLOURS OF PLANTS AND THE ORIGIN OF THE
COLOUR-SENSE

Source of Colouring Matter in Plants — Protective Coloration and Mimicry
in Plants — Attractive Colours of Fruits — Protective Colours of Fruits
—Attractive Colours of Flowers— Attractive Odours in Flowers-
Attractive Grouping of Flowers — Why Alpine Flowers are so Beauti-
ful—Why Allied Species of Flowers differ in Size and Beauty —
Absence of Colour in Wind -fertilised Flowers— The same Theory of
Colour applicable to Animals and Plants— Relation of the Colours

CONTENTS

of Flowers and their Geographical Distribution — Recent Views as
to Direct Action of Light on the Colours of Flowers and Fruits —
Concluding Remarks on the Importance of Colour in the Organic
World — On the Origin of the Colour-sense : Supposed Increase of
Colour-perception within the Historical Period — Concluding Remarks
on the Colour-sense ..... Pages 395-415

VII. THE ANTIQUITY AND ORIGIN OF MAN

Indications of Man's extreme Antiquity — Antiquity of Intellectual Man
— Sculptures on Easter Island — North American Earthworks — The
Great Pyramid— Conclusion .... 416-432

VIII. THE ANTIQUITY OF MAN IN NORTH AMERICA

Ancient Shell Mounds — Man Coeval with Extinct Mammalia — Man in
the Glacial Period— Palaeolithic Implements in North America— The
Auriferous Gravels of California — Fossil Remains under the Ancient
Lava Beds — Works of Art in the Auriferous Gravels — Human
Remains in the Auriferous Gravels — Concluding Remarks on the
Antiquity of Man 433-449

IX. THE DEBT OF SCIENCE TO DAEWIN

The Century before Darwin — The Voyage of the Beagle — The Journal
of ^Researches — Studies of Domestic Animals — Studies of Cultivated
and Wild Plants — Researches on the Cowslip, Primrose, and Loose-
strife—The Struggle for Existence— Geographical Distribution and
Dispersal of Organisms— The Descent of Man and later Works-
Estimate of Darwin's Life- Work .... 450-475

INDEX ... .476

ESSAYS ON NATUEAL SELECTION

ON THE LAW WHICH HAS REGULATED THE INTRODUCTION
OF NEW SPECIES1

Geographical Distribution dependent on Geologic Changes
EVERY naturalist who has directed his attention to the subject
of the geographical distribution of animals and plants must
have been interested in the singular facts which it presents.
Many of these facts are quite different from what would have
been anticipated, and have hitherto been considered as highly
curious, but quite inexplicable. None of the explanations
attempted from the time of Linnaeus are now considered at
all satisfactory ; none of them have given a cause sufficient
to account for the facts known at the time, or comprehensive
enough to include all the new facts which have since been,
and are daily being, added. Of late years, however, a great
light has been thrown upon the subject by geological investi-
gations, which have shown that the present state of the earth
and of the organisms now inhabiting it is but the last stage
of a long and uninterrupted series of changes which it has
undergone, and consequently, that to endeavour to explain
and account for its present condition without any reference
to those changes (as has frequently been done) must lead to
very imperfect and erroneous conclusions.

The facts proved by geology are briefly these : That

1 This article, written at Sarawak in February 1855 and published in the
Annals and Magazine of Natural History, September 1855, was intended to
show that some form of evolution of one species from another was needed in
order to explain the various classes of facts here indicated ; but at that time
no means had been suggested by which the actual change of species could
have been brought about.

NATURAL SELECTION

during an immense but unknown period the surface of the
earth has undergone successive changes ; land has sunk be-
neath the ocean, while fresh land has risen up from it ;
mountain chains have been elevated ; islands have been
formed into continents, and continents submerged till they
have become islands ; and these changes have taken place,
not once merely, but perhaps hundreds, perhaps thousands of
times. — That all these operations have been more or less
continuous but unequal in their progress, and during the
whole series the organic life of the earth has undergone a
corresponding alteration. This alteration also has been
gradual, but complete ; after a certain interval not a single
species existing which had lived at the commencement of the
period. This complete renewal of the forms of life also
appears to have occurred several times. — That from the last
of the geological epochs to the present or historical epoch,
the change of organic life has been gradual : the first appear-
ance of animals now existing can in many cases be traced,
their numbers gradually increasing in the more recent forma-
tions, while other species continually die out and disappear,
so that the present condition of the organic world is clearly
derived by a natural process of gradual extinction and crea-
tion of species from that of the latest geological periods.
We may therefore safely infer a like gradation and natural
sequence from one geological epoch to another.

Now, taking this as a fair statement of the results of
geological inquiry, we see that the present geographical dis-
tribution of life upon the earth must be the result of all the
previous changes, both of the surface of the earth itself and
of its inhabitants. Many causes, no doubt, have operated of
which we must ever remain in ignorance, and we may, there-
fore, expect to find many details very difficult of explanation,
and in attempting to give one, must allow ourselves to call
into our service geological changes which it is highly probable
may have occurred, though we have no direct evidence of
their individual operation.

The great increase of our knowledge within the last twenty
years, both of the present and past history of the organic
world, has accumulated a body of facts which should afford
a sufficient foundation for a comprehensive law embracing and

THE INTRODUCTION OF NEW SPECIES

explaining them all, and giving a direction to new researches.
It is about ten years since the idea of such a law suggested
itself to the writer of this essay, and he has since taken every
opportunity of testing it by all the newly-ascertained facts
with which he has become acquainted, or has been able to
observe himself. These have all served to convince him of
the correctness of his hypothesis. Fully to enter into such a
subject would occupy much space, and it is only in con-
sequence of some views having been lately promulgated, he
believes, in a wrong direction, that he now ventures to present
his ideas to the public, with only such obvious illustrations of
the arguments and results as occur to him in a place far
removed from all means of reference and exact information.

A Law deduced from well-known Geographical and

Geological Facts

The following propositions in Organic Geography and Geo-
logy give the main facts on which the hypothesis is founded.

GKOGRAPHY

1. Large groups, such as classes and orders, are generally
spread over the whole earth, while smaller ones, such as
families and genera, are frequently confined to one portion,
often to a very limited district.

2. In widely distributed families the genera are often
limited in range ; in widely distributed genera well-marked
groups of species are peculiar to each geographical district.

3. When a group is confined to one district, and is rich in
species, it is almost invariably the case that the most closely
allied species are found in the same locality or in closely
adjoining localities, and that therefore the natural sequence
of the species by affinity is also geographical.

4. In countries of a similar climate, but separated by a
wide sea or lofty mountains, the families, genera, and species
of the one are often represented by closely allied families,
genera, and species peculiar to the other.

5. The distribution of the organic world in time is very
similar to its present distribution in space.

NATURAL SELECTION

6. Most of the larger and some small groups extend
through several geological periods.

7. In each period, however, there are peculiar groups,
found nowhere else, and extending through one or several
formations.

8. Species of one genus, or genera of one family occurring
in the same geological time, are more closely allied than those
separated in time.

9. As, generally, in geography no species or genus occurs
in two very distant localities without being also found in
intermediate places, so in geology the life of a species or
genus has not been interrupted. In other words, no group
or species has come into existence twice.

10. The following law may be deduced from these facts :
Every species has come into existence coincident both in space and
time with a pre-existing closely allied species.

This law agrees with, explains, and illustrates all the facts
connected with the following branches of the subject : 1st,
The system of natural affinities. 2d, The distribution of
animals and plants in space. 3d, The same in time, including
all the phenomena of representative groups, and those which
Professor Forbes supposed to manifest polarity. 4th, The
phenomena of rudimentary organs. We will briefly endeavour
to show its bearing upon each of these.

The Form of a true system aj

by this Law

If the law above enunciated be true, it follows that the
natural series of affinities will also represent the order in
which the several species came into existence, each one having
had for its immediate antitype a closely allied species existing
at the time of its origin. It is evidently possible that two or
three distinct species may have had a common antitype, and
that each of these may again have become the antitypes from
which other closely allied species were created. The effect of
this would be, that so long as each species has had but one
new species formed on its model, the line of affinities will be
simple, and may be represented by placing the several species
in direct succession in a straight line. But if two or more
species have been independently formed on the plan of a

THE INTRODUCTION OF NEW SPECIES

common antitype, then the series of affinities will be com-
pound, and can only be represented by a forked or many-
branched line. Now, all attempts at a Natural classification
and arrangement of organic beings show that both these plans
have obtained in creation. Sometimes the series of affinities
can be well represented for a space by a direct progression
from species to species or from group to group, but it is
generally found impossible so to continue. There constantly
occur two or more modifications of an organ or modifications
of two distinct organs, leading us on to two distinct series of
species, which at length differ so much from each other as to
form distinct genera or families. These are the parallel series
or representative groups of naturalists, and they often occur
in different countries, or are found fossil in different forma-
tions. They are said to have an analogy to each other when
they are so far removed from their common antitype as to
differ in many important points of structure, while they still
preserve a family resemblance. We thus see how difficult it
is to determine in every case whether a given relation is an
analogy or an affinity, for it is evident that as we go back
along the parallel or divergent series, towards the common
antitype, the analogy which existed between the two groups
becomes an affinity. We are also made aware of the diffi-
culty of arriving at a true classification, even in a small and
perfect group ; in the actual state of nature it is almost
impossible, the species being so numerous and the modifica-
tions of form and structure so varied, arising probably from
the immense number of species which have served as anti-
types for the existing species, and thus produced a compli-
cated branching of the lines of affinity, as intricate as the
twigs of a gnarled oak or the vascular system of the human
body. Again, if we consider that we have only fragments of
this vast system, the stem and main branches being repre-
sented by extinct species of which we have no knowledge,
while a vast mass of limbs and boughs and minute twigs and
scattered leaves is what we have to place in order, so as to
determine the true position which each originally occupied
with regard to the others, the whole difficulty of the true
Natural System of classification becomes apparent to us.
We shall thus find ourselves obliged to reject all those

NATURAL SELECTION

systems of classification which arrange species or groups in
circles, as well as those which fix a definite number for the
divisions of each group. The latter class have been very
generally rejected by naturalists, as contrary to nature,
notwithstanding the ability with which they have been
advocated ; but the circular system of affinities seems to have
obtained a deeper hold, many eminent naturalists having to
some extent adopted it. We have, however, never been able
to find a case in which the circle has been closed by a direct
and close affinity. In most cases a palpable analogy has been
substituted, in others the affinity is very obscure or altogether
doubtful. The complicated branching of the lines of affinities
in extensive groups must also afford great facilities for giving
a show of probability to any such purely artificial arrange-
ments. Their death-blow was given by the admirable paper
of the lamented Mr. Strickland, published in the Annals of
Natural History, in which he so clearly showed the true
synthetical method of discovering the Natural System.

Geographical Distribution of Organisms
If we now consider the geographical distribution of animals
and plants upon the earth, we shall find all the facts beautifully
in accordance with, and readily explained by, the present
hypothesis. A country having species, genera, and whole
families peculiar to it, will be the necessary result of its
having been isolated for a long period, sufficient for many
series of species to have been created on the type of pre-
existing ones, which, as well as many of the earlier -formed
species, have become extinct, and thus made the groups
appear isolated. If in any case the antitype had an extensive
range, two or more groups of species might have been formed,
each varying from it in a different manner, and thus producing
several representative or analogous groups. The Sylviadse of
Europe and the Sylvicolidae of North America, the Heliconidae
of South America and the Euploeas of the East, the group of
Trogons inhabiting Asia and that peculiar to South America,
are examples that may be accounted for in this manner.

Such phenomena as are exhibited by the Galapagos Islands,
which contain little groups of plants and animals peculiar to
themselves, but most nearly allied to those of South America,

THE INTRODUCTION OF NEW SPECIES

have not hitherto received any, even a conjectural explana-
tion. The Galapagos are a volcanic group of high antiquity,
and have probably never been more closely connected with
the continent than they are at present. They must have
been first peopled, like other newly-formed islands, by the
action of winds and currents, and at a period sufficiently
remote to have had the original species die out, and the modi-
fied prototypes only remain. In the same way we can account
for the separate islands having each their peculiar species,
either on the supposition that the same original emigration
peopled the whole of the islands with the same species from
which differently modified prototypes were created, or that the
islands were successively peopled from each other, but that
new species have been created in each on the plan of the pre-
existing ones. St. Helena is a similar case of a very ancient
island having obtained an entirely peculiar, though limited,
flora. On the other hand, no example is known of an island
which can be proved geologically to be of very recent origin
(late in the Tertiary, for instance), and yet possesses generic
or family groups, or even many species peculiar to itself.

When a range of mountains has attained a great eleva-
tion, and has so remained during a long geological period,
the species of the two sides at and near their bases will be
often very different, representative species of some genera
occurring, and even whole genera being peculiar to one side
only, as is remarkably seen in the case of the Andes and
Rocky Mountains. A similar phenomenon occurs when an
island has been separated from a continent at a very early
period. The shallow sea between the Peninsula of Malacca,
Java, Sumatra, and Borneo was probably a continent or large
island at an early epoch, and may have become submerged as
the volcanic ranges of Java and Sumatra were elevated ; the
organic results we see in the very considerable number of
species of animals common to some or all of these countries,
while at the same time a number of closely allied repre-
sentative species exist peculiar to each, showing that a con-
siderable period has elapsed since their separation. The facts
of geographical distribution and of geology may thus mutu-
ally explain each other in doubtful cases, should the prin-
ciples here advocated be clearly established.

10 NATURAL SELECTION i

In all those cases in which an island has been separated
from a continent, or raised by volcanic or coralline action
from the sea, or in which a mountain-chain has been elevated
in a recent geological epoch, the phenomena of peculiar
groups or even of single representative species will not exist.
Our own island is an example of this, its separation from the
continent being geologically very recent, and we have con-
sequently scarcely a species which is peculiar to it ; while the
Alpine range, one of the most recent mountain elevations,
separates faunas and floras which scarcely differ more than
may be due to climate and latitude alone.

The series of facts alluded to in Proposition (3), of closely
allied species in rich groups being found geographically near
each other, is most striking and important. Mr. Lovell
Eeeve has well exemplified it in his able and interesting
paper on the Distribution of the Bulimi. It is also seen in
the Humming-birds and Toucans, little groups of two or three
closely allied species being often found in the same or closely
adjoining districts, as we have had the good fortune of per-
sonally verifying. Fishes give evidence of a similar kind :
each great river has its peculiar genera, and in more extensive
genera its groups of closely allied species. But it is the same
throughout Nature ; every class and order of animals will
contribute similar facts. Hitherto no attempt has been
made to explain these singular phenomena, or to show how
they have arisen. Why are the genera of Palms and of
Orchids in almost every case confined to one hemisphere?
Why are the closely allied species of brown-backed Trogons
all found in the East, and the green-backed in the West ?
Why are the Macaws and the Cockatoos similarly restricted ?
Insects furnish a countless number of analogous examples —
the Goliathi of Africa, the Ornithopteras of the Indian
Islands, the Heliconidse of South America, the Danaidae of
the East, and in all the most closely allied species found in
geographical proximity. The question forces itself upon
every thinking mind, Why are these things so ? They
could not be as' they are had no law regulated their creation
and dispersion. The law here enunciated not merely ex-
plains but necessitates the facts we see to exist, while the
vast and long - continued geological changes of the earth

THE INTRODUCTION OF NEW SPECIES

readily account for the exceptions and apparent discrepancies
that here and there occur. The writer's object in putting
forward his views in the present imperfect manner is to
submit them to the test of other minds, and to be made
aware of all the facts supposed to be inconsistent with them.
As his hypothesis is one which claims acceptance solely as
explaining and connecting facts which exist in nature, he
expects facts alone to be brought to disprove it, not h priori
arguments against its probability.

Geological Distribution of the Forms of Life
The phenomena of geological distribution are exactly
analogous to those of geography. Closely allied species are
found associated in the same beds, and the change from
species to species appears to have been as gradual in time as
in space. Geology, however, furnishes us with positive proof
of the extinction and production of species, though it does
not inform us how either has taken place. The extinction of
species, however, offers but little difficulty, and the modus
operandi has been well illustrated by Sir C. Lyell in his ad-
mirable Principles. Geological changes, however gradual,
must occasionally have modified external conditions to such
an extent as to have rendered the existence of certain species
impossible. The extinction would in most cases be effected
by a gradual dying-out, but in some instances there might
have been a sudden destruction of a species of limited range.
To discover how the extinct species have from time to time
been replaced by new ones down to the very latest geological
period, is the most difficult, and at the same time the most
interesting problem in the natural history of the earth. The
present inquiry, which seeks to eliminate from known facts
a law which has determined, to a certain degree, what species
could and did appear at a given epoch, may, it is hoped, be
considered as one step in the right direction towards a com-
plete solution of it.

High Organisation of very ancient Animals consistent

with this Law

Much discussion has of late years taken place on the
question whether the succession of life upon the globe has

12 NATURAL SELECTION I

been from a lower to a higher degree of organisation. The
admitted facts seem to show that there has been a general,
but not a detailed progression. Mollusca and Radiata existed
before Vertebrata, and the progression from Fishes to Reptiles
and Mammalia, and also from the lower mammals to the
higher, is indisputable. On the other hand, it is said that
the Mollusca and Radiata of the very earliest periods were
more highly organised than the great mass of those now
existing, and that the very first fishes that have been dis-
covered are by no means the lowest organised of the class.
Now it is believed the present hypothesis will harmonise with
all these facts, and in a great measure serve to explain them ;
for though it may appear to some readers essentially a theory
of progression, it is in reality only one of gradual change.
It is, however, by no means difficult to show that a real pro-
gression in the scale of organisation is perfectly consistent
with all the appearances, and even with apparent retrogression,
should such occur.

Returning to the analogy of a branching tree, as the best mode
of representing the natural arrangement of species and their
successive creation, let us suppose that at an early geological
epoch any group (say a class of the Mollusca) has attained to
a great richness of species and a high organisation. Now let
this great branch of allied species, by geological mutations,
be completely or partially destroyed. Subsequently a new
branch springs from the same trunk — that is to say, new
species are successively created, having for their antitypes the
same lower organised species which had served as the anti-
types for the former group, but which have survived the
modified conditions which destroyed it. This new group
being subject to these altered conditions, has modifications of
structure and organisation given to it, and becomes the repre-
sentative group of the former one in another geological form-
ation. It may, however, happen, that though later in time,
the new series of species may never attain to so high a degree
of organisation as those preceding it, but in its turn become
extinct, and give place to yet another modification from the
same root, which may be of higher or lower organisation,
more or less numerous in species, and more or less varied in
form and structure, than either of those which preceded it.

i THE INTRODUCTION OF NEW SPECIES 13

Again, each of these groups may not have become totally
extinct, but may have left a few species, the modified proto-
types of which have existed in each succeeding period, a faint
memorial of their former grandeur and luxuriance. Thus
every case of apparent retrogression may be in reality a pro-
gress, though an interrupted one : when some monarch of the
forest loses a limb, it may be replaced by a feeble and sickly
substitute. The foregoing remarks appear to apply to the
case of the Mollusca, which, at a very early period, had
reached a high organisation and a great development of forms
and species in the testaceous Cephalopoda. In each succeed-
ing age modified species and genera replaced the former ones
which had become extinct, and as we approach the present
era, but few and small representatives of the group remain,
while the Gasteropods and Bivalves have acquired an immense
preponderance. In the long series of changes the earth has
undergone, the process of peopling it with organic beings has
been continually going on, and whenever any of the higher
groups have become nearly or quite extinct, the lower forms
which have better resisted the modified physical conditions
have served as the antitypes on which to found the new
races. In this manner alone, it is believed, can the represent-
ative groups at successive periods, and the risings and fallings
in the scale of organisation, be in every case explained.

Objections to Forbes' Theory of Polarity
The hypothesis of polarity, recently put forward by Pro-
fessor Edward Forbes to account for the abundance of generic
forms at a very early period and at present, while in the in-
termediate epochs there is a gradual diminution and impover-
ishment, till the minimum occurred at the confines of the
Palaeozoic and Secondary epochs, appears to us quite unneces-
sary, as the facts may be readily accounted for on the principles
already laid down. Between the Palaeozoic and Neozoic
periods of Professor Forbes there is scarcely a species in com-
mon, and the greater parts of the genera and families also
disappear, to be replaced by new ones. It is almost univer-
sally admitted that such a change in the organic world must
have occupied a vast period of time. Of this interval we
have no record ; probably because the whole area of the early

14 NATURAL SELECTION j

formations now exposed to our researches was elevated at the
end of the Palaeozoic period, and remained so through the
interval required for the organic changes which resulted in
the fauna and flora of the Secondary period. The records of
this interval are buried beneath the ocean which covers three-
fourths of the globe. Now it appears highly probable that a
long period of quiescence or stability in the physical condi-
tions of a district would be most favourable to the existence
of organic life in the greatest abundance, both as regards
individuals and also as to variety of species and generic group,
just as we now find that the places best adapted to the rapid
growth and increase of individuals also contain the greatest
profusion of species and the greatest variety of forms, — the
tropics in comparison with the temperate and arctic regions.
On the other hand, it seems no less probable that a change in
the physical conditions of a district, even small in amount if
rapid, or even gradual if to a great amount, would be highly
unfavourable to the existence of individuals, might cause the
extinction of many species, and would probably be equally
unfavourable to the creation of new ones. In this too we
may find an analogy with the present state of our earth, for
it has been shown to be the violent extremes and rapid
changes of physical conditions, rather than the actual mean
state in the temperate and frigid zones, which renders them
less prolific than the tropical regions, as exemplified by the
great distance beyond the tropics to which tropical forms
penetrate when the climate is equable, and also by the rich-
ness in species and forms of tropical mountain regions which
principally differ from the temperate zone in the uniformity
of their climate. However this may be, it seems a fair
assumption that during a period of geological repose the new
species which we know to have been created would have
appeared, that the creations would then exceed in number the
extinctions, and therefore the number of species would increase.
In a period of geological activity, on the other hand, it seems
probable that the extinctions might exceed the creations, and
the number of species consequently diminish. That such
effects did take place in connection with the causes to which
we have imputed them, is shown in the case of the Coal
formation, the faults and contortions of which show a period

i THE INTRODUCTION OF NEW SPECIES 15

of great activity and violent convulsions, and it is in the
formation immediately succeeding this that the poverty of
forms of life is most apparent. We have then only to sup-
pose a long period of somewhat similar action during the vast
unknown interval at the termination of the Palaeozoic period,
and then a decreasing violence or rapidity through the
Secondary period, to allow for the gradual repopulation of
the earth with varied forms, and the whole of the facts are
explained.1 We thus have a clue to the increase of the forms
of life during certain periods, and their decrease during others,
without recourse to any causes but those we know to have
existed, and to effects fairly deducible from them. The pre-
cise manner in which the geological changes of the early
formations were effected is so extremely obscure, that when
we can explain important facts by a retardation at one time
and an acceleration at another of a process which we know
from its nature and from observation to have been unequal, —
a cause so simple may surely be preferred to one so obscure
and hypothetical as polarity.

I would also venture to suggest some reasons against the
very nature of the theory of Professor Forbes. Our know-
ledge of the organic world during any geological epoch is
necessarily very imperfect. Looking at the vast numbers of
species and groups that have been discovered by geologists,
this may be doubted ; but we should compare their numbers
not merely with those that now exist upon the earth, but with
a far larger amount. We have no reason for believing that
the number of species on the earth at any former period was
much less than at present ; at all events the aquatic portion,
with which geologists have most acquaintance, was probably
often as great or greater. Now we know that there have
been many complete changes of species ; new sets of organisms
have many times been introduced in place of old ones which
have become extinct, so that the total amount which have
existed on the earth from the earliest geological period must
have borne about the same proportion to those now living, as
the whole human race who have lived and died upon the

1 Professor Ramsay has since shown that a glacial epoch probably occurred
at the time of the Permian formation, which will more satisfactorily account
for the comparative poverty of species.

16 NATURAL SELECTION i

earth to the population at the present time. Again, at each
epoch, the whole earth was, no doubt, as now, more or less the
theatre of life, and as the successive generations of each species
died, their exuviae and preservable parts would be deposited
over every portion of the then existing seas and oceans, which
we have reason for supposing to have been more, rather than
less, extensive than at present. In order then to understand
our possible knowledge of the early world and its inhabitants,
we must compare, not the area of the whole field of our geo-
logical researches with the earth's surface, but the area of the
examined portion of each formation separately with the whole
earth. For example, during the Silurian period all the earth
was Silurian, and animals were living and dying and deposit-
ing their remains more or less over the whole area of the
globe, and they were probably (the species at least) nearly as
varied in different latitudes and longitudes as at present.
What proportion do the Silurian districts bear to the whole
surface of the globe, land and sea (for far more extensive
Silurian districts probably exist beneath the ocean than above
it), and what portion of the known Silurian districts has been
actually examined for fossils? Would the area of rock
actually laid open to the eye be the thousandth or the ten-
thousandth part of the earth's surface? Ask the same
question with regard to the Oolite or the Chalk, or even to
particular beds of these when they differ considerably in their
fossils, and you may then get some notion of how small a
portion of the whole we know.

But yet more important is the probability, nay, almost the
certainty, that whole formations containing the records of
vast geological periods are entirely buried beneath the ocean,
and for ever beyond our reach. Most of the gaps in the
geological series may thus be filled up, and vast numbers of
unknown and unimaginable animals, which might help to
elucidate the affinities of the numerous isolated groups which
are a perpetual puzzle to the zoologist, may there be buried,
till future revolutions may raise them in their turn above the
waters, to afford materials for the study of whatever race of
intelligent beings may then have succeeded us. These con-
siderations must lead us to the conclusion that our knowledge
of the whole series of the former inhabitants of the earth is

i THE INTRODUCTION OF NEW SPECIES 17

necessarily most imperfect and fragmentary, — as much so as
our knowledge of the present organic world would be, were
we forced to make our collections and observations only in
spots equally limited in area and in number with those
actually laid open for the collection of fossils. Now, the
hypothesis of Professor Forbes is essentially one that assumes
to a great extent the completeness of our knowledge of the
whole series of organic beings which have existed on the
earth. This appears to be a fatal objection to it, inde-
pendently of all other considerations. It may be said that
the same objections exist against every theory on such a sub-
ject, but this is not necessarily the case. The hypothesis put
forward in this paper depends in no degree upon the com-
pleteness of our knowledge of the former condition of the
organic world, but takes what facts we have as fragments of
a vast whole, and deduces from them something of the nature
and proportions of that whole which we can never know in
detail. It is founded upon isolated groups of facts, recognises
their isolation, and endeavours to deduce from them the
nature of the intervening portions.

Rudimentary Organs

Another important series of facts, quite in accordance
with, and even necessary deductions from, the law now
developed, are those of rudimentary organs. That these
really do exist, and -in most cases have no special function in
the animal economy, is admitted by the first authorities in
comparative anatomy. The minute limbs hidden beneath the
skin in many of the snake-like lizards, the anal hooks of the
boa constrictor, the complete series of jointed finger -bones in
the paddle of the Manatus and whale, are a few of the most
familiar instances. In botany a similar class of facts has been long
recognised. Abortive stamens, rudimentary floral envelopes
and undeveloped carpels, are of the most frequent occurrence.
To every thoughtful naturalist the question must arise, What
are these for 1 What have they to do with the great laws of
creation? Do they not teach us something of the system
of Nature ? If each species has been created independently,
and without any necessary relations with pre-existing species,
what do these rudiments, these apparent imperfections mean ?
c

18 NATURAL SELECTION i

There must be a cause for them ; they must be the necessary
results of some great natural law. Now, if, as it has been
endeavoured to be shown, the great law which has regulated
the peopling of the earth with animal and vegetable life is,
that every change shall be gradual ; that no new creature
shall be formed widely differing from anything before exist-
ing ; that in this, as in everything else in nature, there shall
be gradation and harmony, — then these rudimentary organs
are necessary, and are an essential part of the system of
nature. Ere the higher Vertebrata were formed, for instance,
many steps were required, and many organs had to undergo
modifications from the rudimental condition in which only
they had as yet existed. We still see remaining an antitypal
sketch of a wing adapted for flight in the scaly flapper of the
penguin, and limbs first concealed beneath the skin, and then
weakly protruding from it, were the necessary gradations
before others should be formed fully adapted for locomotion.1
Many more of these modifications should we behold, and more
complete series of them, had we a view of all the forms which
have ceased to live. The great gaps that exist between fishes,
reptiles, birds, and mammals would then, no doubt, be
softened down by intermediate groups, and the whole organic
world would be seen to be an unbroken and harmonious
system.

Conclusion

It has now been shown, though most briefly and imper-
fectly, how the law that " Every species has come into existence
coincident both in time and space with a pre-existing closely allied
species" connects together and renders intelligible a vast
number of independent and hitherto unexplained facts. The
natural system of arrangement of organic beings, their geo-
graphical distribution, their geological sequence, the pheno-
mena of representative and substituted groups in all their
modifications, and the most singular peculiarities of anatomical
structure, are all explained and illustrated by it, in perfect
accordance with the vast mass of facts which the researches of
modern naturalists have brought together, and, it is believed,

1 The theory of Natural Selection has now taught us that these are not the
steps by which limbs have been formed ; and that most rudimentary organs
have been produced by abortion, owing to disuse, as explained by Mr. Darwin.

i THE INTRODUCTION OF NEW SPECIES 19

not materially opposed to any of them. It also claims a
superiority over previous hypotheses, on the ground that it
not merely explains, but necessitates what exists. Granted
the law, and many of the most important facts in Nature
could not have been otherwise, but are almost as necessary
deductions from it as are the elliptic orbits of the planets
from the law of gravitation.

INTRODUCTORY NOTE TO CHAPTER II IN PRESENT EDITION

As this chapter sets forth the main features of a theory
identical with that discovered by Mr. Darwin many years
before but not then published, and as it has thus an historical
interest, a few words of personal statement may be permissible.
After writing the preceding paper the question of how changes
of species could have been brought about was rarely out of
my mind, but no satisfactory conclusion was reached till
February 1858. At that time I was suffering from a rather
severe attack of intermittent fever at Ternate in the Moluccas,
and one day while lying on my bed during the cold fit,
wrapped in blankets, though the thermometer was at 88°
F., the problem again presented itself to me, and something
led me to think of the "positive checks" described by Malthus
in his "Essay on Population," a work I had read several
years before, and which had made a deep and permanent
impression on my mind. These checks — war, disease, famine
and the like — must, it occurred to me, act on animals as well
as on man. Then I thought of the enormously rapid multi-
plication of animals, causing these checks to be much more
effective in them than in the case of man ; and while ponder-
ing vaguely on this fact there suddenly flashed upon me the
idea of the survival of the fittest — that the individuals removed
by these checks must be on the whole inferior to those that
survived. In the two hours that elapsed before my ague fit
was over I had thought out almost the whole of the theory,
and the same evening I sketched the draft of my paper, and
in the two succeeding evenings wrote it out in full, and sent
it by the next post to Mr. Darwin. Up to this time the only
letters I had received from him were those printed in the
second volume of his Life and Letters, (vol. ii. pp. 95 and 108),

INTRODUCTORY NOTE TO CHAPTER II 21

in which he speaks of its being the twentieth year since he
" opened his first note-book on the question how and in what
way do species and varieties differ from each other," and after '
referring to oceanic islands, the means of distribution of land-
shells, etc., added : " My work, on which I have now been at
work more or less for twenty years, will not fix or settle any-
thing; but I hope it will aid by giving a large collection of
facts, with one definite end." The words I have italicised,
and the whole tone of his letters, led me to conclude that he
had arrived at no definite view as to the origin of species, and
I fully anticipated that my theory would be new to him,
because it seemed to me to settle a great deal. The imme-
diate result of my paper was that Darwin was induced at
once to prepare for publication his book on the Origin of
Species in the condensed form in which it appeared, instead of
waiting an indefinite number of years to complete a work on
a much larger scale which he had partly written, but which
in all probability would not have carried conviction to so
many persons in so short a time. I feel much satisfaction in
having thus aided in bringing about the publication of this
celebrated book, and with the ample recognition by Darwin
himself of my independent discovery of " natural selection."
(See Origin of Species, 6th ed., introduction, p. 1, and Life and
Letters, vol. ii. chap, iv., pp. 115-129 and 145.)

II

ON THE TENDENCY OF VARIETIES TO DEPART INDEFINITELY
FROM THE ORIGINAL TYPE

Instability of Varieties supposed to prove the permanent
distinctness of Species

ONE of the strongest arguments which have been adduced
to prove the original and permanent distinctness of species is,
that varieties produced in a state of domesticity are more or
less unstable, and often have a tendency, if left to them-
selves, to return to the normal form of the parent species ;
and this instability is considered to be a distinctive peculi-
arity of all varieties, even of those occurring among wild
animals in a state of nature, and to constitute a provision
for preserving unchanged the originally created distinct
species.

In the absence or scarcity of facts and observations as to
varieties occurring among wild animals, this argument has had
great weight with naturalists, and has led to a very general
and somewhat prejudiced belief in the stability of species.
Equally general, however, is the belief in what are called
" permanent or true varieties," — races of animals which con-
tinually propagate their like, but which differ so slightly
(although constantly) from some other race, that the one is
considered to be a variety of the other. Which is the variety
and which the original species, there is generally no means
of determining, except in those rare cases in which the
one race has been known to produce an offspring unlike itself
and resembling the other. This, however, would seem quite
incompatible with the "permanent invariability of species,"

ii ON THE TENDENCY OF VARIETIES, ETC. 23

but the difficulty is overcome by assuming that such varieties
have strict limits, and can never again vary further from the
original type, although they may return to it, which, from the
analogy of the domesticated animals, is considered to be highly
probable, if not certainly proved.

It will be observed that this argument rests entirely on the
assumption that varieties occurring in a state of nature are
in all respects analogous to or even identical with those of
domestic animals, and are governed by the same laws as
regards their permanence or further variation. But it is the
object of the present paper to show that this assumption is
altogether false, that there is a general principle in nature
which will cause many varieties to survive the parent species,
and to give rise to successive variations departing further and
further from the original type, and which also produces, in
domesticated animals, the tendency of varieties to return to
the parent form.

The Struggle for Existence

The life of wild animals is a struggle for existence. The
full exertion of all their faculties and all their energies is
required to preserve their own existence and provide for that
of their infant offspring. The possibility of procuring food
during the least favourable seasons, and of escaping the
attacks of their most dangerous enemies, are the primary
conditions which determine the existence both of individuals
and of entire species. These conditions will also determine
the population of a species ; and by a careful consideration of
all the circumstances we may be enabled to comprehend, and
in some degree to explain, what at first sight appears so
inexplicable — the excessive abundance of some species, while
others closely allied to them are very rare.

The Law of Population of Species

The general proportion that must obtain between certain
groups of animals is readily seen. Large animals cannot be
so abundant as small ones ; the carnivora must be less
numerous than the herbivora ; eagles and lions can never be
so plentiful as pigeons and antelopes ; and the wild asses of
the Tartarian deserts cannot equal in numbers the horses of

24 NATURAL SELECTION n

the more luxuriant prairies and pampas of America. The
greater or less fecundity of an animal is often considered to
be one of the chief causes of its abundance or scarcity ; but a
consideration of the facts will show us that it really has little
or nothing to do with the matter. Even the least prolific of
animals would increase rapidly if unchecked, whereas it is
evident that the animal population of the globe must be
stationary, or perhaps, through the influence of man, decreasing.
Fluctuations there may be ; but permanent increase, except in
restricted localities, is almost impossible. For example, our
own observation must convince us that birds do not go on
increasing every year in a geometrical ratio, as they would
do were there not some powerful check to their natural
increase. Very few birds produce less than two young ones
each year, while many have six, eight, or ten ; four will
certainly be below the average ; and if we suppose that each
pair produce young only four times in their life, that will
also be below the average, supposing them not to die either
by violence or want of food. Yet at this rate how tremendous
would be the increase in a few years from a single pair ! A
simple calculation will show that in fifteen years each pair of
birds would have increased to nearly ten millions ! l whereas
we have no reason to believe that the number of the birds of
any country increases at all in fifteen or in one hundred and
fifty years. With such powers of increase the population
must have reached its limits, and have become stationary, in
a very few years after the origin of each species. It is
evident, therefore, that each year an immense number of
birds must perish — as many in fact as are born ; and as on
the lowest calculation the progeny are each year twice as
numerous as their parents, it follows that, whatever be the
average number of individuals existing in any given country,
twice that number must perish annually, — a striking result, but
one which seems at least highly probable, and is perhaps
under rather than over the truth. It would therefore appear
that, so far as the continuance of the species and the keeping
up the average number of individuals are concerned, large
broods are superfluous. On the average all above one become

1 This is under estimated. The number would really amount to more
than two thousand millions !

ii ON THE TENDENCY OF VARIETIES, ETC. 25

food for hawks and kites, wild cats or weasels, or perish of
cold and hunger as winter comes on. This is strikingly
proved by the case of particular species; for we find that
their abundance in individuals bears no relation whatever to
their fertility in producing offspring.

Perhaps the most remarkable instance of an immense bird
population is that of the passenger pigeon of the United
States, which lays only one, or at most two eggs, and is said
to rear generally but one young one. Why is this bird so
extraordinarily abundant, while others producing two .or three
times as many young are much less plentiful ? The explana-
tion is not difficult. The food most congenial to this species,
and on which it thrives best, is abundantly distributed over
a very extensive region, offering such differences of soil and
climate, that in one part or another of the area the supply
never fails. The bird is capable of a very rapid and long-
continued flight, so that it can pass without fatigue over the
whole of the district it inhabits, and as soon as the supply of
food begins to fail in one place is able to discover a fresh
feeding-ground. This example strikingly shows us that the
procuring a constant supply of wholesome food is almost the
sole condition requisite for ensuring the rapid increase of a
given species, since neither the limited fecundity nor the un-
restrained attacks of birds of prey and of man are here
sufficient to check it. In no other birds are these peculiar
circumstances so strikingly combined. Either their food is
more liable to failure, or they have not sufficient power of
wing to search for it over an extensive area, or during some
season of the year it becomes very scarce, and less wholesome
substitutes have to be found ; and thus, though more fertile
in offspring, they can never increase beyond the supply of
food in the least favourable seasons.

Many birds can only exist by migrating, when their food
becomes scarce, to regions possessing a milder, or at least a
different climate, though, as these migrating birds are seldom
excessively abundant, it is evident that the countries they
visit are still deficient in a constant and abundant supply of
wholesome food. Those whose organisation does not permit
them to migrate when their food becomes periodically scarce,
can never attain a large population. This is probably the

NATURAL SELECTION

reason why woodpeckers are scarce with us, while in the
tropics they are among the most abundant of solitary birds.
Thus the house sparrow is more abundant than the redbreast,
because its food is more constant and plentiful, — seeds of
grasses being preserved during the winter, and our farm-yards
and stubble-fields furnishing an almost inexhaustible supply.
Why, as a general rule, are aquatic, and especially sea-birds,
very numerous in individuals 1 Not because they are more
prolific than others, generally the contrary ; but because their
food never fails, the sea-shores and river-banks daily swarm-
ing with a fresh supply of small mollusca and Crustacea.
Exactly the same laws will apply to mammals. Wild cats
are prolific and have few enemies ; why then are they never
as abundant as rabbits ? The only intelligible answer is, that
their supply of food is more precarious. It appears evident,
therefore, that so long as a country remains physically un-
changed, the numbers of its animal population cannot
materially increase. If one species does so, some others
requiring the same kind of food must diminish in proportion.
The numbers that die annually must be immense ; and as the
individual existence of each animal depends upon itself, those
that die must be the weakest — the very young, the aged, and
the diseased — while those that prolong their existence can
only be the most perfect in health and vigour — those who are
best able to obtain food regularly, and avoid their numerous
enemies. It is, as we commenced by remarking, " a struggle
for existence," in which the weakest and least perfectly
organised must always succumb.

The Abundance or Rarity of a Species dependent upon its more or

less perfect Adaptation to the Conditions of Existence
It seems evident that what takes place among the indi-
viduals of a species must also occur among the several allied
species of a group, — viz., that those which are best adapted
to obtain a regular supply of food, and to defend themselves
against the attacks of their enemies and the vicissitudes of the
seasons, must necessarily obtain and preserve a superiority in
population ; while those species which, from some defect of
power or organisation, are the least capable of counteracting
the vicissitudes of food-supply, etc., must diminish in numbers,

ii ON THE TENDENCY OF VARIETIES, ETC. 27

and, in extreme cases, become altogether extinct. Between
these extremes the species will present various degrees of
capacity for ensuring the means of preserving life ; and it is
thus we account for the abundance or rarity of species. Our
ignorance will generally prevent us from accurately tracing
the effects to their causes ; but could we become perfectly
acquainted with the organisation and habits of the various
species of animals, and could we measure the capacity of each
for performing the different acts necessary to its safety and
existence under all the varying circumstances by which it is
surrounded, we might be able even to calculate the pro-
portionate abundance of individuals which is the necessary
result.

If now we have succeeded in establishing these two points
— 1st, that the animal population of a country is generally
stationary, being kept down by a periodical deficiency of food, and
other checks ; and, 2d, that the comparative abundance or scarcity
of the individuals of the several species is entirely due to their
organisation and resulting habits, which, rendering it more difficult
to procure a regular supply of food and to provide for their personal
safety l in some cases than in others, can only be balanced by a
difference in the population which have to exist in a given area —
we shall be in a condition to proceed to the consideration of
varieties, to which the preceding remarks have a direct and
very important application.

Useful Variations mil tend to Increase ; useless or hurtful
Variations to Diminish

Most or perhaps all the variations from the typical form
of a species must have some definite effect, however slight, on
the habits or capacities of the individuals. Even a change of
colour might, by rendering them more or less distinguishable,
affect their safety; a greater or less development of hair
might modify their habits. More important changes, such as
an increase in the power or dimensions of the limbs or any of
the external organs, would more or less affect their mode of
procuring food or the range of country which they could in-

1 ' ' And that of their offspring " should have been added. But it must
be remembered that the writer had no opportunity of correcting the proofs of
this paper.

NATURAL SELECTION

habit. It is also evident that most changes would affect,
either favourably or adversely, the powers of prolonging
existence. An antelope with shorter or weaker legs must
necessarily suffer more from the attacks of the feline carni-
vora ; the passenger pigeon with less powerful wings would
sooner or later be affected in its powers of procuring a regular
supply of food ; and in both cases the result must necessarily
be a diminution of the population of the modified species. If,
on the other hand, any species should produce a variety
having slightly increased powers of preserving existence, that
variety must inevitably in time acquire a superiority in
numbers. These results must follow as surely as old age, in-
temperance, or scarcity of food produce an increased mortality.
In both cases there may be many individual exceptions : but
on the average the rule will invariably be found to hold good.
All varieties will therefore fall into two classes — those which
under the same conditions would never reach the population
of the parent species, and those which would in time obtain
and keep a numerical superiority. Now, let some alteration
of physical conditions occur in the district — a long period of
drought, a destruction of vegetation by locusts, the irruption
of some fresh carnivorous animal seeking " pastures new " —
any change in fact tending to render existence more difficult
to the species in question, and tasking its utmost powers to
avoid complete extermination, — it is evident that, of all the
individuals composing the species, those forming the least
numerous and most feebly organised variety would suffer
first, and, were the pressure severe, must soon become extinct.
The same causes continuing in action, the parent species would
next suffer, would gradually diminish in numbers, and with
a recurrence of similar unfavourable conditions might also
become extinct. The superior variety would then alone
remain, and on a return to favourable circumstances would
rapidly increase in numbers and occupy the place of the
extinct species and variety.

Superior Varieties will ultimately Extirpate the original Species

The variety would now have replaced the species, of which
it would be a more perfectly developed and more highly
organised form. It would be in all respects better adapted

ii ON THE TENDENCY OF VARIETIES, ETC. 29

to secure its safety, and to prolong its individual existence
and that of the race. Such a variety could not return to the
original form ; for that form is an inferior one, and could
never compete with it for existence. Granted, therefore, a
" tendency " to reproduce the original type of the species, still
the variety must ever remain preponderant in numbers, and
under adverse physical conditions again alone survive. But
this new, improved, and populous race might itself, in course
of time, give rise to new varieties, exhibiting several diverging
modifications of form, any of Avhich, tending to increase the
facilities for preserving existence, must, by the same general
law, in their turn become predominant. Here, then, we have
progression and continued divergence deduced from the general
laws which regulate the existence of animals in a state of
nature, and from the undisputed fact that varieties do fre-
quently occur. It is not, however, contended that this result
would be invariable ; a change of physical conditions in the
district might at times materially modify it, rendering the
race which had been the most capable of supporting existence
under the former conditions now the least so, and even
causing the extinction of the newer and, for a time, superior
race, while the old or parent species and its first inferior
varieties continued to flourish. Variations in unimportant
parts might also occur, having no perceptible effect on the
life-preserving powers ; and the varieties so furnished might
run a course parallel with the parent species, either giving
rise to further variations or returning to the former type.
All we argue for is, that certain varieties have a tendency to
maintain their existence longer than the original species, and
this tendency must make itself felt ; for though the doctrine
of chances or averages can never be trusted on a limited scale,
yet, if applied to high numbers, the results come nearer to
what theory demands, and, as we approach to an infinity
of examples, become strictly accurate. Now the scale on
which nature works is so vast — the numbers of individuals
and the periods of time with which she deals approach
so near to infinity — that any cause, however slight, and
however liable to be veiled and counteracted by accidental
circumstances, must in the end produce its full legitimate
results.

30 NATURAL SELECTION

The Partial Reversion of Domesticated Varieties explained

Let us now turn to domesticated animals, and inquire how
varieties produced among them are affected by the principles
here enunciated. The essential difference in the condition of
wild and domestic animals is this, — that among the former,
their well - being and very existence depend upon the full
exercise and healthy condition of all their senses and physical
powers, whereas, among the latter, these are only partially
exercised, and in some cases are absolutely unused. A wild
animal has to search, and often to labour, for every mouthful
of food — to exercise sight, hearing, and smell in seeking it,
and in avoiding dangers, in procuring shelter from the inclem-
ency of the seasons, and in providing for the subsistence
and safety of its offspring. There is no muscle of its body
that is not called into daily and hourly activity ; there is no
sense or faculty that is not strengthened by continual exercise.
The domestic animal, on the other hand, has food provided
for it, is sheltered, and often confined, to guard it against
the vicissitudes of the seasons, is carefully secured from the
attacks of its natural enemies, and seldom even rears its young
without human assistance. Half of its senses and faculties
become quite useless, and the other half are but occasionally
called into feeble exercise, while even its muscular system is
only irregularly brought into action.

Now when a variety of such an animal occurs having
increased power or capacity in any organ or sense, such
increase is totally useless, is never called into action, and may
even exist without the animal ever becoming aware of it. In
the wild animal, on the contrary, all its faculties and powers
being brought into full action for the necessities of existence,
any increase becomes immediately available, is strengthened
by exercise, and must even slightly modify the food, the habits,
and the whole economy of the race. It creates as it were a
new animal, one of superior powers, and which will necessarily
increase in numbers and outlive those which are inferior to it.

Again, in the domesticated animal all variations have an
equal chance of continuance ; and those which would de-
cidedly render a wild animal unable to compete with its
fellows and continue its existence are no disadvantage what-

ii ON THE TENDENCY OF VARIETIES, ETC. 31

ever in a state of domesticity. Our quickly fattening pigs,
short -legged sheep, pouter pigeons, and poodle dogs could
never have come into existence in a state of nature, because
the very first steps towards such inferior forms would have
led to the rapid extinction of the race ; still less could they
now exist in competition with their wild allies. The great
speed but slight endurance of the racehorse, the unwieldly
strength of the ploughman's team, would both be useless in
a state of nature. If turned wild on the pampas, such
animals would probably soon become extinct, or under
favourable circumstances might each gradually lose those
extreme qualities which would never be called into action,
and in a few generations revert to a common type, which
must be that in which the various powers and faculties are so
proportioned to each other as to be best adapted to procure
food and secure safety, — that in which, by the full exercise of
every part of its organisation, the animal can alone continue
to live. Domestic varieties, when turned wild, must return
to something near the type of the original wild stock, or
become altogether extinct}-

We see, then, that no inferences as to the permanence of
varieties in a state of nature can be deduced from the ob-
servations of those occurring among domestic animals. The
two are so much opposed to each other in every circumstance
of their existence, that what applies to the one is almost sure
not to apply to the other. Domestic animals are abnormal,
irregular, artificial ; they are subject to variations which
never occur, and never can occur, in a state of nature : their
very existence depends altogether on human care — so far are
many of them removed from that just proportion of faculties,
that true balance of organisation, by means of which alone an
animal left to its own resources can preserve its existence and
continue its race.

Lamarck's Hypothesis very different from that now advanced
The hypothesis of Lamarck — that progressive changes in
species have been produced by the attempts of animals to

1 That is, they will vary, and the variations which tend to adapt them to
the wild state, and therefore approximate them to wild animals, will be pre-
served. Those individuals which do not vary sufficiently will perish.

32 NATURAL SELECTION H

increase the development of their own organs, and thus
modify their structure and habits — has been repeatedly and
easily refuted by all writers on the subject of varieties and
species, and it seems to have been considered that when this
was done the whole question has been finally settled ; but
the view here developed renders such an hypothesis quite
unnecessary, by showing that similar results must be pro-
duced by the action of principles constantly at work in
nature. The powerful retractile talons of the falcon and
the cat tribes have not been produced or increased by the
volition of those animals ; but among the different varieties
which occurred in the earlier and less highly organised forms
of these groups, those always survived longest which had the
greatest facilities for seizing their prey. Neither did the
giraffe acquire its long neck by desiring to reach the foliage
of the more lofty shrubs, and constantly stretching its neck
for the purpose, but because any varieties which occurred
among its antitypes with a longer neck than usual at once
secured a fresh range of pasture over the same ground as their
shorter-necked companions, and on the first scarcity of food were
thereby enabled to outlive them. Even the peculiar colours of
many animals, more especially of insects, so closely resem-
bling the soil or leaves or bark on which they habitually
reside, are explained on the same principle ; for though in
the course of ages varieties of many tints may have occurred,
yet those races having colours best adapted to concealment from their
enemies would inevitably survive the longest. We have also
here an acting cause to account for that balance so often
observed in nature, — a deficiency in one set of organs always
being compensated by an increased development of some
others — powerful wings accompanying weak feet, or great
velocity making up for the absence of defensive weapons ;
for it has been shown that all varieties in which an un-
balanced deficiency occurred could not long continue their
existence. The action of this principle is exactly like that
of the centrifugal governor of the steam-engine, which checks
and corrects any irregularities almost before they become
evident ; and in like manner no unbalanced deficiency in the
animal kingdom can ever reach any conspicuous magnitude,
because it would make itself felt at the very first step, by

ii ON THE TENDENCY OF VARIETIES, ETC. 33

rendering existence difficult and extinction almost sure soon
to follow. An origin such as is here advocated will also
agree with the peculiar character of the modifications of form
and structure which obtain in organised beings — the many
lines of divergence from a central type, the increasing effici-
ency and power of a particular organ through a succession of
allied species, and the remarkable persistence of unimportant
parts, such as colour, texture of plumage and hair, form of
horns or crests, through a series of species differing consider-
ably in more essential characters. It also furnishes us with
a reason for that " more specialised structure " which Pro-
fessor Owen states to be a characteristic of recent compared
with extinct forms, and which would evidently be the result
of the progressive modification of any organ applied to a
special purpose in the animal economy.

Conclusion

We believe we have now shown that there is a tendency
in nature to the continued progression of certain classes of
varieties further and further from the original type — a pro-
gression to which there appears no reason to assign any
definite limits — and that the same principle which produces
this result in a state of nature will also explain why domestic
varieties have a tendency, when they become wild, to revert
to the original type. This progression, by minute steps, in
various directions, but always checked and balanced by the
necessary conditions, subject to which alone existence can be
preserved, may, it is believed, be followed out so as to
agree with all the phenomena presented by organised
beings, their extinction and succession in past ages, and all
the extraordinary modifications of form, instinct, and habits
which they exhibit.

Ill

MIMICRY, AND OTHER PROTECTIVE RESEMBLANCES AMONG

ANIMALS

THERE is no more convincing proof of the truth of a com-
prehensive theory than its power of absorbing and finding
a place for new facts, and its capability of interpreting
phenomena which had been previously looked upon as un-
accountable anomalies. It is thus that the law of universal
gravitation and the undulatory theory of light have become
established and universally accepted by men of science.
Fact after fact has been brought forward as being apparently
inconsistent with them, and one after another these very
facts have been shown to be the consequences of the laws
they were at first supposed to disprove. A false theory will
never stand this test. Advancing knowledge brings to light
whole groups of facts which it cannot deal with, and its
advocates steadily decrease in numbers, notwithstanding the
ability and scientific skill with which it may have been
supported. The great name of Edward Forbes did not
prevent his theory of " Polarity in the distribution of Organic
beings in Time " from dying a natural death ; but the most
striking illustration of the behaviour of a false theory is to
be found in the " Circular and Quinarian System " of classi-
fication propounded by MacLeay, and developed by Swain-
son, with an amount of knowledge and ingenuity that has
rarely been surpassed. This theory was eminently attract-
ive, both from its symmetry and completeness, and from
the interesting nature of the varied analogies and affinities

1 First published in the Westminster Review, July 1867 ; reprinted in
1870 with additions and corrections.

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 35

which it brought to light and made use of. The series of
Natural History volumes in Lardner's Cabinet Cyclopcedia, in
which Mr. Swainson developed it in most departments of the
animal kingdom, made it widely known ; and in fact for a
long time these were the best and almost the only popular
text-books for the rising generation of naturalists. It was
favourably received too by the older school, which was per-
haps rather an indication of its unsoundness. A considerable
number of well-known naturalists either spoke approvingly of
it, or advocated similar principles, and for a good many years
it was decidedly in the ascendant. With such a favourable
introduction, and with such talented exponents, it must have
become established if it had had any germ of truth in it ;
yet it quite died out in a few short years ; its very existence
is now a matter of history ; and so rapid was its fall that
its talented creator, Swainson, perhaps lived to be the last
man who believed in it.

Such is the course of a false theory. That of a true one
is very different, as may be well seen by the progress of
opinion on the subject of Natural Selection. In less than
eight years The Origin of Species has produced conviction
in the minds of a majority of the most eminent living men
of science. New facts, new problems, new difficulties as they
arise are accepted, solved, or removed by this theory ; and its
principles are illustrated by the progress and conclusions of
every well established branch of human knowledge. It is the
object of the present chapter to show how it has recently been
applied to connect together and explain a variety of curious
facts which had long been considered as inexplicable anomalies.

of the Principle of Utility
Perhaps no principle has ever been announced so fertile in
results as that which Mr. Darwin so earnestly impresses upon
us, and which is indeed a necessary deduction from the
theory of Natural Selection, namely — that none of the
definite facts or organic nature, no special organ, no char-
acteristic form of marking, no peculiarities of instinct or of
habit, no relations between species or between groups of
species — can exist, but which must now be or once have been
useful to the individuals or the races which possess them.

36 NATURAL SELECTION in

This great principle gives us a clue which we can follow out
in the study of many recondite phenomena, and leads us to
seek a meaning and a purpose of some definite character in
minutiae which we should otherwise be almost sure to pass
over as insignificant or unimportant.

Popular Theories of Colour in Animals
The adaptation of the external colouring of animals to
their conditions of life has long been recognised, and has been
imputed either to an originally created specific peculiarity,
or to the direct action of climate, soil, or food. Where the
former explanation has been accepted it has completely
checked inquiry, since we could never get any further than
the fact of the adaptation. There was nothing more to be
known about the matter. The second explanation was soon
found to be quite inadequate to deal with all the varied
phases of the phenomena, and to be contradicted by many
well known facts. For example, wild rabbits are always of
gray or brown tints well suited for concealment among grass
and fern. But when these rabbits are domesticated, without
any change of climate or food, they vary into white or black,
and these varieties may be multiplied to any extent, forming
white or black races. Exactly the same thing has occurred
with pigeons ; and in the case of rats and mice, the white
variety has not been shown to be at all dependent on altera-
tion of climate, food, or other external conditions. In many
cases the wings of an insect not only assume the exact tint of
the bark or leaf it is accustomed to rest on, but the form and
veining of the leaf or the exact rugosity of the bark is
imitated ; and these detailed modifications cannot be reason-
ably imputed to climate or to food, since in many cases the
species does not feed on the substance it resembles, and when
it does, no reasonable connection can be shown to exist
between the supposed cause and the effect produced. It was
reserved for the theory of Natural Selection to solve all these
problems, and many others which were not at first supposed
to be directly connected with them. To make these latter
intelligible, it will be necessary to give a sketch of the whole
series of phenomena which may be classed under the head of
useful or protective resemblances.

PROTECTIVE RESEMBLANCES AMONG ANIMALS 37

Importance of Concealment as Influencing

Concealment, more or less complete, is useful to many
animals, and absolutely essential to some. Those which have
numerous enemies from which they cannot escape by rapidity
of motion find safety in concealment. Those which prey
upon others must also be so constituted as not to alarm them
by their presence or their approach, or they would soon die
of hunger. Now it is remarkable in how many cases nature
gives this boon to the animal, by colouring it with such tints
as may best serve to enable it to escape from its enemies or
to entrap its prey. Desert animals as a rule are desert-
coloured. The lion is a typical example of this, and must be
almost invisible when crouched upon the sand or among
desert rocks and stones. Antelopes are all more or less
sandy -coloured. The camel is pre-eminently so. The
Egyptian cat and the Pampas cat are sandy or earth-coloured.
The Australian kangaroos are of the same tints, and the
original colour of the wild horse is supposed to have been a
sandy or clay-colour.

The desert birds are still more remarkably protected by
their assimilative hues. The stonechats, the larks, the quails,
the goatsuckers and the grouse, which abound in the North
African and Asiatic deserts, are all tinted and mottled so as
to resemble with wonderful accuracy the average colour and
aspect of the soil in the district they inhabit. The Rev. H.
Tristram, in his account of the ornithology of North Africa
in the first volume of the Ibis, says : "In the desert, where
neither trees, brushwood, nor even undulation of the surface
afford the slightest protection to its foes, a modification of
colour which shall be assimilated to that of the surrounding
country is absolutely necessary. Hence without exception the
upper plumage of every bird, whether lark, chat, sylvain, or
sand-grouse, and also the fur of all the smaller mammals, and
the skin of all the snakes and lizards, is of one uniform isabelline
or sand colour." After the testimony of so able an observer
it is unnecessary to adduce further examples of the protective
colours of desert animals.

Almost equally striking are the cases of arctic animals
possessing the white colour that best conceals them upon

38 NATURAL SELECTION in

snowfields and icebergs. The polar bear is the only bear
that is white, and it lives constantly among snow and ice.
The arctic fox, the ermine, and the alpine hare change to
white in winter only, because in summer white would be
more conspicuous than any other colour, and therefore a
danger rather than a protection; but the American polar
hare, inhabiting regions of almost perpetual snow, is white all
the year round. Other animals inhabiting the same Northern
regions do not, however, change colour. The sable is a good
example, for throughout the severity of a Siberian winter it
retains its rich brown fur. But its habits are such that it
does not need the protection of colour, for it is said to be able
to subsist on fruits and berries in winter, and to be so active
upon the trees as to catch small birds among the branches.
So also the woodchuck of Canada has a dark-brown fur ; but
then it lives in burrows and frequents river banks, catching
fish and small animals that live in or near the water.

Among birds, the ptarmigan is a fine example of protective
colouring. Its summer plumage so exactly harmonises with
the lichen-coloured stones among which it delights to sit, that
a person may walk through a flock of them without seeing a
single bird ; while in winter its white plumage is an almost
equal protection. The snow-bunting, the jer-falcon, and the
snowy owl are also white-coloured birds inhabiting the arctic
regions, and there can be little doubt but that their colouring
is to some extent protective.

Nocturnal animals supply us with equally good illustrations.
Mice, rats, bats and moles possess the least conspicuous of
hues, and must be quite invisible at times when any light
colour would be instantly seen. Owls and goatsuckers are of
those dark mottled tints that will assimilate with bark and
lichen, and thus protect them during the day, and at the
same time be inconspicuous in the dusk.

It is only in the tropics, among forests which never lose
their foliage, that we find whole groups of birds whose chief
colour is green. The parrots are the most striking example,
but we have also a group of green pigeons in the East ; and
the barbets, leaf-thrushes, bee-eaters, white-eyes, turacos, and
several smaller groups, have so much green in their plumage
as to tend greatly to conceal them among the foliage.

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 39

Special Modifications of Colawr

The conformity of tint which has been so far shown to
exist between animals and their habitations is of a somewhat
general character; we will now consider the cases of more
special adaptation. If the lion is enabled by his sandy
colour readily to conceal himself by merely crouching down
upon the desert, how, it may be asked, do the elegant markings
of the tiger, the jaguar, and the other large cats, agree
with this theory ? We reply that these are generally cases
of more or less special adaptation. The tiger is a jungle
animal, and hides himself among tufts of grass or of bamboos,
and in these positions the vertical stripes with which his
body is adorned must so assimilate with the vertical stems of
the bamboo as to assist greatly in concealing him from his
approaching prey.1 How remarkable it is that besides the
lion and tiger, almost all the other large cats are arboreal in
their habits, and almost all have ocellated or spotted skins,
which must certainly tend to blend them with the background
of foliage ; while the one exception, the puma, has an ashy
.brown uniform fur, and has the habit of clinging so closely
to a limb of a tree while waiting for his prey to pass beneath
as to be hardly distinguishable from the bark.

Among birds, the ptarmigan, already mentioned, must be
considered a remarkable case of special adaptation. Another
is a South American goatsucker (Caprimulgus rupestris), which
rests in the bright sunshine on little bare rocky islets in the
Upper Kio Negro, where its unusually light colours so closely
resemble those of the rock and sand that it can scarcely be
detected till trodden upon.

The Duke of Argyll, in his Eeign of Law, has pointed out
the admirable adaptation of the colours of the woodcock to
its protection. The various browns and yellows and pale
ash-colour that occur in fallen leaves are all reproduced in its
plumage, so that when, according to its habit, it rests upon
the ground under trees, it is almost impossible to detect it.
In snipes the colours are modified so as to be equally in
harmony with the prevalent forms and colours of marshy
vegetation. Mr. J. M. Lester, in a paper read before the

1 This suggestion has been since confirmed. See Darwinism, p. 199.

40 NATURAL SELECTION in

Eugby School Natural History Society, observes : " The
wood-dove, when perched amongst the branches of its favour-
ite fir, is scarcely discernible ; whereas, were it among some
lighter foliage, the blue and purple tints in its plumage would
far sooner betray it. The robin redbreast too, although it
might be thought that the red on its breast made it much
easier to be seen, is in reality not at all endangered by it,
since it generally contrives to get among some russet or
yellow fading leaves, where the red matches very well with
the autumn tints, and the brown of the rest of the body with
the bare branches."

Reptiles offer us many similar examples. The most
arboreal lizards, the iguanas, are as green as the leaves they
feed upon, and the slender whip-snakes are rendered almost
invisible as they glide among the foliage by a similar color-
ation. How difficult it is sometimes to catch sight of the
little green tree-frogs sitting on the leaves of a small plant
enclosed in a glass case in the Zoological Gardens ; yet how
much better concealed must they be among the fresh green
damp foliage of a marshy forest. There is a North American
frog found on lichen -covered rocks and walls, which is so
coloured as exactly to resemble them, and as long as it
remains quiet would certainly escape detection. Some of the
geckos which cling motionless on the trunks of trees in the
tropics are of such curiously marbled colours as to match
exactly with the bark they rest upon.

In every part of the tropics there are tree-snakes that
twist among boughs and shrubs, or lie coiled up on the dense
masses of foliage. These are of many distinct groups, and
comprise both venomous and harmless genera ; but almost all
of them are of a beautiful green colour, sometimes more or
less adorned with white or dusky bands and spots. There
can be little doubt that this colour is doubly useful to them,
since it will tend to conceal them from their enemies, and
will lead their prey to approach them unconscious of danger.
Dr. Gunther informs me that there is only one genus of true
arboreal snakes (Dipsas) whose colours are rarely green, but
are of various shades of black, brown, and olive, and these
are all nocturnal reptiles, and there can be little doubt
conceal themselves during the day in holes, so that the green

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 41

protective tint would be useless to them, and they accordingly
retain the more usual reptilian hues.

Fishes present similar instances. Many flat fish, as for
example the flounder and the skate, are exactly the colour of
the gravel or sand on which they habitually rest. Among
the marine flower gardens of an Eastern coral reef the fishes
present every variety of gorgeous colour, while the river fish
even of the tropics rarely if ever have gay or conspicuous
markings. A very curious case of this kind of adaptation
occurs in the sea-horses (Hippocampus) of Australia, some of
which bear long foliaceous appendages resembling seaweed,
and are of a brilliant red colour ; and they are known to live
among seaweed of the same hue, so that when at rest they
must be quite invisible. There are now in the aquarium of
the Zoological Society some slender green pipe-fish which
fasten themselves to any object at the bottom by their
prehensile tails, and float about with the current, looking
exactly like some simple cylindrical algae.

It is, however, in the insect world that this principle of
the adaptation of animals to their environment is most fully
and strikingly developed. In order to understand how
general this is, it is necessary to enter somewhat into details,
as we shall thereby be better able to appreciate the signifi-
cance of the still more remarkable phenomena we shall
presently have to discuss. It seems to be in proportion to
their sluggish motions or the absence of other means of
defence, that insects possess the protective colouring. In the
tropics there are thousands of species of insects which rest
during the day clinging to the bark of dead or fallen trees ;
and the greater portion of these are delicately mottled with
gray and brown tints, which, though symmetrically disposed
and infinitely varied, yet blend so completely with the usual
colours of the bark, that at two or three feet distance they
are quite undistinguishable. In some cases a species is
known to frequent only one species of tree. This is the case
with the common South American long -horned beetle
(Onychocerus scorpio), which, Mr. Bates informed me, is
found only on a rough -barked tree, called Tapiriba, on the
Amazon. It is very abundant, but so exactly does it resemble
the bark in colour and rugosity, and so closely does it cling

42 NATURAL SELECTION in

to the branches, that until it moves it is absolutely invisible !
An allied species (0. concentricus) is found only at Para, on a
distinct species of tree, the bark of which it resembles with
equal accuracy. Both these insects are abundant, and we
may fairly conclude that the protection they derive from this
strange concealment is at least one of the causes that enable
the race to nourish.

Many of the species of Cicindela, or tiger beetle, will
illustrate this mode of protection. Our common Cicindela
campestris frequents grassy banks, and is of a beautiful green
colour, while C. maritima, which is found only on sandy sea-
shores, is of a pale bronzy yellow, so as to be almost invisible.
A great number of the species found by myself in the Malay
islands are similarly protected. The beautiful Cicindela
gloriosa, of a very deep velvety green colour, was only taken
upon wet mossy stones in the bed of a mountain stream, where
it was with the greatest difficulty detected. A large brown
species (C. heros) was found chiefly on dead leaves in forest
paths ; and one which was never seen except on the wet mud
of salt marshes was of a glossy olive so exactly the colour of the
mud as only to be distinguished, when the sun shone, by its
shadow ! Where the sandy beach was coralline and nearly
white, I found a very pale Cicindela ; wherever it was volcanic
and black, a dark species of the same genus was sure to be
met with.

There are in the East small beetles of the family Bupres-
tidae which generally rest on the midrib of a leaf, and the
naturalist often hesitates before picking them off, so closely
do they resemble pieces of bird's dung. Kirby and Spence
mention the small beetle Onthophilus sulcatus as being like
the seed of an umbelliferous plant; and another, a small
weevil, which is much persecuted by predatory beetles of the
genus Harpalus, is of the exact colour of loamy soil, and was
found to be particularly abundant in loam pits. Mr. Bates
mentions a small beetle (Chlamys pilula) which was undis-
tinguishable by the eye from the dung of caterpillars, while
some of the Cassidae, from their hemispherical forms and pearly
gold colour, resemble glittering dew-drops upon the leaves.

A number of our small brown and speckled weevils at the
approach of any object roll off the leaf they are sitting on, at

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 43

the same time drawing in their legs and antennae, which fit so
perfectly into cavities for their reception that the insect
becomes a mere oval brownish lump, which it is hopeless to
look for among the similarly coloured little stones and earth
pellets among which it lies motionless.

The distribution of colour in butterflies and moths re-
spectively is very instructive from this point of view. The
former have all their brilliant colouring on the upper surface
of all four wings, while the under surface is almost always
soberly coloured, and often very dark and obscure. The
moths on the contrary have generally their chief colour on
the hind wings only, the upper wings being of dull, sombre,
and often imitative tints, and these generally conceal the
hind wings when the insects are in repose. This arrange-
ment of the colours is therefore eminently protective, because
the butterfly always rests with his wings raised so as to con-
ceal the dangerous brilliancy of his upper surface. It is
probable that if we watched their habits sufficiently we should
find the under surface of the wings of butterflies very fre-
quently imitative and protective. Mr. T. W. Wood has
pointed out that the little orange-tip butterfly often rests in
the evening on the green and white flower heads of an
umbelliferous plant, the wild chervil,1 and that when observed
in this position the beautiful green and white mottling of the
under surface completely assimilates with the flower heads
and renders the creature very difficult to be seen. It is
probable that the rich dark colouring of the under side of our
peacock, tortoiseshell, and red-admiral butterflies answers a
similar purpose.

Two curious South American butterflies that always settle
on the trunks of trees (Gynecia dirce and Callizona acesta)
have the under surface curiously striped and mottled, and
when viewed obliquely must closely assimilate with the appear-
ance of the furrowed bark of many kinds of trees. But the most
wonderful and undoubted case of protective resemblance in a
butterfly which I have ever seen, is that of the common Indian
Kallima inachis, and its Malayan ally, Kallima paralekta.
The upper surface of these insects is very striking and showy,
as they are of a large size, and are adorned with a broad band
1 Antlmscus sylvestris.

44 NATURAL SELECTION in

of rich orange on a deep-bluish ground. The under side is
very variable in colour, so that out of fifty specimens no two
can be found exactly alike, but every one of them will be of
some shade of ash or brown or ochre, such as are found
among dead, dry, or decaying leaves. The apex of the upper
wings is produced into an acute point, a very common form
in the leaves of tropical shrubs and trees, and the lower
wings are also produced into a short narrow tail. Between
these two points runs a dark curved line exactly representing
the midrib of a leaf, and from this radiate on each side a few
oblique lines, which serve to indicate the lateral veins of a
leaf. These marks are more clearly seen on the outer por-
tion of the base of the wings, and on the inner side towards
the middle and apex, and it is very curious to observe how
the usual marginal and transverse striae of the group are here
modified and strengthened so as to become adapted for an
imitation of the venation of a leaf. We come now to a still more
extraordinary part of the imitation, for we find representations
of leaves in every stage of decay, variously blotched and mil-
dewed and pierced with holes, and in many cases irregularly
covered with powdery black dots gathered into patches and spots,
so closely resembling the various kinds of minute fungi that
grow on dead leaves that it is impossible to avoid thinking at
first sight that the butterflies themselves have been attacked
by real fungi.

But this resemblance, close as it is, would be of little use
if the habits of the insect did not accord with it. If the
butterfly sat upon leaves or upon flowers, or opened its wings
so as to expose the upper surface, or exposed and moved its
head and antennae as many other butterflies do, its disguise
would be of little avail. We might be sure, however, from
the analogy of many other cases, that the habits of the insect
are such as still further to aid its deceptive garb ; but we are
not obliged to make any such supposition, since I myself had
the good fortune to observe scores of Kallima paralekta, in
Sumatra, and to capture many of them, and can vouch for the
accuracy of the following details. These butterflies frequent
dry forests and fly very swiftly. They were never seen to
settle on a flower or a green leaf, but were many times lost
sight of in a bush or tree of dead leaves. On such occasions

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 45

they were generally searched for in vain, for while gazing
intently at the very spot where one had disappeared, it would
often suddenly dart out, and again vanish twenty or fifty
yards farther on. On one or two occasions the insect was
detected reposing, and it could then be seen how completely
it assimilates itself to the surrounding leaves. It sits on a
nearly upright twig, the wings fitting closely back to back,
concealing the antennae and head, which are drawn up between
their bases. The little tails of the hind wing touch the
branch, and form a perfect stalk to the leaf, which is sup-
ported in its place by the claws of the middle pair of feet,
which are slender and inconspicuous. The irregular outline of
the wings gives exactly the perspective effect of a shrivelled
leaf. We thus have size, colour, form, markings, and habits
all combining together to produce a disguise which may be
said to be absolutely perfect ; and the protection which it
affords is sufficiently indicated by the abundance of the in-
dividuals that possess it.

The Rev. Joseph Greene has called attention to the strik-
ing harmony between the colours of those British moths
which are on the wing in autumn and winter, and the prevail-
ing tints of nature at those seasons. In autumn various
shades of yellow and brown prevail, and he shows that out of
fifty-two species that fly at this season, no less than forty-two
are of corresponding colours. Orgyia antiqua, 0. gonostigma,
the genera Xanthia, Glaea, and Ennomos are examples. In
winter, gray and silvery tints prevail, and the genus Chematobia
and several species of Hybernia which fly during this season
are of corresponding hues. No doubt if the habits of moths
in a state of nature were more closely observed, we should
find many cases of special protective resemblance. A few
such have already been noticed. Agriopis aprilina, Acronycta
psi, and many other moths which rest during the day on the
north side of the trunks of trees, can with difficulty be dis-
tinguished from the gray and green lichens that cover them.
The lappet moth (Gastropacha querci) closely resembles both
in shape and colour a brown dry leaf; and the well-known
buff-tip moth, when at rest, is like the broken end of a lichen-
covered branch. There are some of the small moths which
exactly resemble the dung of birds dropped on leaves, and on

46 NATURAL SELECTION in

this point Mr. A. Sidgwick, in a paper read before the Rugby
School Natural History Society, gives the following original
observation : " I myself have more than once mistaken Cilix
compressa, a little white and gray moth, for a piece of bird's
dung dropped upon a leaf, and vice versd the dung for the moth.
Bryophila Glandifera and Perla are the very image of the
mortar walls on which they rest ; and only this summer, in
Switzerland, I amused myself for some time in watching a
moth, probably Larentia tripunctaria, fluttering about quite
close to me, and then alighting on a wall of the stone of the
district which it so exactly matched as to be quite invisible a
couple of yards off." There are probably hosts of these re-
semblances which have not been observed, owing to the diffi-
culty of finding many of the species in their stations of natural
repose. Caterpillars are also similarly protected. Many
exactly resemble in tint the leaves they feed upon ; others are
like little brown twigs, and many are so strangely marked or
humped, that when motionless they can hardly be taken to be
living creatures at all. Mr. Andrew Murray has remarked
how closely the larva of the peacock moth (Saturnia pavonia-
minor) harmonises in its ground colour with that of the young
buds of heather on which it feeds, and that the pink spots
with which it is decorated correspond with the flowers and
flower-buds of the same plant.

The whole order of Orthoptera, grasshoppers, locusts,
crickets, etc., are protected by their colours harmonising with
that of the vegetation or the soil on which they live, and in
no other group have we such striking examples of special
resemblance. Most of the tropical Mantidae and Locustidse
are of the exact tint of the leaves on which they habitually
repose, and many of them in addition have the veinings of
their wings modified so as exactly to imitate that of a leaf.
This is carried to the furthest possible extent in the wonder-
ful genus, Phy Ilium, the " walking leaf," in which not only
are the wings perfect imitations of leaves in every detail, but
the thorax and legs are flat, dilated, and leaf-like ; so that
when the living insect is resting among the foliage on which
it feeds, the closest observation is often unable to distinguish
between the animal and the vegetable.

The whole family of the Phasmidae, or spectres, to which

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 47

this insect belongs, is more or less imitative, and a great
number of the species are called " walking-stick insects," from
their singular resemblance to twigs and branches. Some of
these are a foot long and as thick as one's finger, and their
whole colouring, form, rugosity, and the arrangement of the
head, legs, and antennae are such as to render them absolutely
identical in appearance with dead sticks. They hang loosely
about shrubs in the forest, and have the extraordinary habit
of stretching out their legs unsymmetrically, so as to render
the deception more complete. One of these creatures ob-
tained by myself in Borneo (Ceroxylus laceratus) was covered
over with foliaceous excrescences of a clear olive green colour,
so as exactly to resemble a stick grown over by a creeping
moss or jungermannia. The Dyak who brought it me
assured me it was grown over with moss although alive, and
it was only after a most minute examination that I could
convince myself it was not so.

We need not adduce any more examples to show how
important are the details of form and of colouring in animals,
and that their very existence may often depend upon their
being by these means concealed from their enemies. This
kind of protection is found apparently in every class and
order, for it has been noticed wherever we can obtain suffi-
cient knowledge of the details of an animal's life-history. It
varies in degree, from the mere absence of conspicuous colour
or a general harmony with the prevailing tints of nature, up
to such a minute and detailed resemblance to inorganic or
vegetable structures as to realise the talisman of the fairy
tale, and to give its possessor the power of rendering itself
invisible.

Theory of Protective Colouring

We will now endeavour to show how these wonderful
resemblances have most probably been brought about. Re-
turning to the higher animals, let us consider the remarkable
fact of the rarity of white colouring in the mammalia or birds
of the temperate or tropical zones in a state of nature. There
is not a single white land-bird or quadruped in Europe, except
the few arctic or alpine species, to which white is a protective
colour. Yet in many of these creatures there seems to be no

NATURAL SELECTION

inherent tendency to avoid white, for directly they are
domesticated white varieties arise, and appear to thrive as
well as others. We have white mice and rats, white cats,
horses, dogs and cattle, white poultry, pigeons, turkeys and
ducks, and white rabbits. Some of these animals have been
domesticated for a long period, others only for a few centuries;
but in almost every case in which an animal has been
thoroughly domesticated, parti-coloured and white varieties
are produced and become permanent.

It is also well known that animals in a state of nature
produce white varieties occasionally. Blackbirds, starlings,
and crows are occasionally seen white, as well as elephants,
deer, tigers, hares, moles, and many other animals ; but in
no case is a permanent white race produced. Now there are
no statistics to show that the normal-coloured parents produce
white offspring oftener under domestication than in a state of
nature, and we have no right to make such an assumption if
the facts can be accounted for without it. But if the colours
of animals do really, in the various instances already adduced,
serve for their concealment and preservation, then white or
any other conspicuous colour must be hurtful, and must in
most cases shorten an animal's life. A white rabbit would
be more surely the prey of hawk or buzzard, and the white
mole, or field mouse, could not long escape from the vigilant
owl. So, also, any deviation from those tints best adapted
to conceal a carnivorous animal would render the pursuit of
its prey much more difficult, would place it at a disadvantage
among its fellows, and in a time of scarcity would probably
cause it to starve to death. On the other hand, if an animal
spreads from a temperate into an arctic district, the conditions
are changed. During a large portion of the year, and just
when the struggle for existence is most severe, white is the
prevailing tint of nature, and dark colours will be the most
conspicuous. The white varieties will now have an advan-
tage ; they will escape from their enemies or will secure food,
while their brown companions will be devoured or will starve;
and as "like produces like" is the established rule in nature,
the white race will become permanently established, and dark
varieties, when they occasionally appear, will soon die out
from their want of adaptation to their environment. In each

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 49

case the fittest will survive, and a race will be eventually
produced adapted to the conditions in which it lives.

We have here an illustration of the simple and effectual
means by which animals are brought into harmony with the
rest of nature. That slight amount of variability in every
species, which we often look upon as something accidental or
abnormal, or so insignificant as to be hardly worthy of notice,
is yet the foundation of all those wonderful and harmonious
resemblances which play such an important part in the
economy of nature. Variation is generally very small in
amount,1 but it is all that is required, because the change in
the external conditions to which an animal is subject is
generally very slow and intermittent. When these changes
have taken place too rapidly, the result has often been the
extinction of species ; but the general rule is, that climatal
and geological changes go on slowly, and the slight but con-
tinual variations in the colour, form, and structure of all
animals have furnished individuals adapted to these changes,
and who have become the progenitors of modified races.
Rapid multiplication, incessant slight variation, and survival
of the fittest — these are the laws which ever keep the organic
world in harmony with the inorganic, and with itself. These
are the laws which we believe have produced all the cases of
protective resemblance already adduced, as well as those still
more curious examples we have yet to bring before our
readers.

It must always be borne in mind that the more wonderful
examples, in which there is not only a general but a special
resemblance — as in the walking leaf, the mossy phasma, and
the leaf -winged butterfly — represent those few instances in
which the process of modification has been going on during
an immense series of generations. They all occur in the
tropics, where the conditions of existence are the most
favourable, and where climatic changes have for long periods
been hardly perceptible. In most of them favourable varia-
tions both of colour, form, structure, and instinct or habit,
must have occurred to produce the perfect adaptation we now
behold. All these are known to vary, and favourable varia-

1 Later research has shown that variation is more frequent and of greater
amouiit than at first supposed. See Darwinism, chap. iii.
E

50 NATURAL SELECTION in

tions, when not accompanied by others that were unfavourable,
would certainly survive. At one time a little step might be
made in this direction, at another time in that — a change of
conditions might sometimes render useless that which it had
taken ages to produce — great and sudden physical modifica-
tions might often produce the extinction of a race just as it
was approaching perfection, and a hundred checks of which
we can know nothing may have retarded the progress towards
perfect adaptation ; so that we can hardly wonder at there
being so few cases in which a completely successful result has
been attained as shown by the abundance and wide diffusion
of the creatures so protected.

Objection that Colour, as being dangerous, should not exist in
Nature

It is as well here to reply to an objection that will no
doubt occur to many readers — that if concealment is so useful
to all animals, and so easily brought about by variation and
survival of the fittest, there ought to be no conspicuously-
coloured creatures; and they will perhaps ask how we
account for the brilliant birds, and painted snakes, and
gorgeous insects that occur abundantly all over the world.
It will be advisable to answer this question rather fully, in
order that we may be prepared to understand the phenomena
of " mimicry," which it is the special object of this chapter to
illustrate and explain.

The slightest observation of the life of animals will show
us that they escape from their enemies and obtain their food
in an infinite number of ways, and that their varied habits
and instincts are in every case adapted to the conditions of
their existence. The porcupine and the hedgehog have a
defensive armour that saves them from the attacks of most
animals. The tortoise is not injured by the conspicuous
colours of his shell, because that shell is in most cases an
effectual protection to him. The skunks of North America
find safety in their power of emitting an unbearably offensive
odour ; the beaver in its aquatic habits and solidly constructed
abode. In some cases the chief danger to an animal occurs
at one particular period of its existence, and if that is guarded
against its numbers can easily be maintained. This is the

in PROTECTIVE EESEMBLANCES AMONG ANIMALS 51

case with many birds, the eggs and young of which are
especially obnoxious to danger, and we find accordingly a
variety of curious contrivances to protect them. We have
nests carefully concealed, hung from the slender extremities
of grass or boughs over water, or placed in the hollow of a
tree with a very small opening. When these precautions are
successful, so many more individuals will be reared than can
possibly find food during the least favourable seasons, that
there will always be a number of weakly and inexperienced
young birds who will fall a prey to the enemies of the race,
and thus render necessary for the stronger and healthier
individuals no other safeguard than their strength and activity.
The instincts most favourable to the production and rearing
of offspring will in these cases be most important, and the
survival of the fittest will act so as to keep up and advance
those instincts, while other causes which tend to modify
colour and marking may continue their action almost un-
checked.

It is perhaps in insects that we may best study the varied
means by which animals are defended or concealed. One of
the uses of the phosphorescence with which many insects are
furnished is probably to frighten away their enemies; for
Kirby and Spence state that a ground-beetle (Carabus) has
been observed running round and round a luminous centipede
as if afraid to attack it. An immense number of insects have
stings, and some stingless ants of the genus Polyrachis are
armed with strong and sharp spines on the back, which must
render them unpalatable to many of the smaller insectivorous
birds. Many beetles of the family Curculionidse have the
wing cases and other external parts so excessively hard, that
they cannot be pinned without first drilling a hole to receive
the pin, and it is probable that all such find a protection in
this excessive hardness. Great numbers of insects hide them-
selves among the petals of flowers, or in the cracks of bark
and timber; and finally, extensive groups and even whole
orders have a more or less powerful and disgusting smell and
taste, which they either possess permanently, or can emit at
pleasure. The attitudes of some insects may also protect
them, as the habit of turning up the tail by the harmless
rove-beetles (Staphylindidse) no doubt leads other animals

52 NATURAL SELECTION in

besides children to the belief that they can sting. The
curious attitude assumed by sphinx caterpillars is probably a
safeguard, as well as the blood -red tentacles which can
suddenly be thrown out from the neck by the caterpillars of
all the true swallow-tailed butterflies.

It is among the groups that possess some of these varied
kinds of protection in a high degree that we find the greatest
amount of conspicuous colour, or at least the most complete
absence of protective imitation. The stinging Hymenoptera,
wasps, bees, and hornets are, as a rule, very showy and
brilliant insects, and there is not a single instance recorded
in which any one of them is coloured so as to resemble a
vegetable or inanimate substance. The Chrysididse, or golden
wasps, which do not sting, possess as a substitute the power
of rolling themselves up into a ball, which is almost as hard
and polished as if really made of metal, — and they are all
adorned with the most gorgeous colours.1 The whole order
Hemiptera (comprising the bugs) emit a powerful odour, and
they present a very large proportion of gay-coloured and con-
spicuous insects. The lady -birds (Coccinellidse) and their
allies the Eumorphidae, are often brightly spotted, as if to
attract attention; but they can both emit fluids of a very
disagreeable nature; they are certainly rejected by some birds
and are probably never eaten by any.

The great family of ground-beetles (Carabidee) almost all
possess a disagreeable and some a very pungent smell, and a
few, called bombardier beetles, have the peculiar faculty of
emitting a jet of very volatile liquid, which appears like a
puff of smoke, and is accompanied by a distinct crepitating
explosion. It is probably because these insects are mostly
nocturnal and predacious that they do not present more vivid
hues. They are chiefly remarkable for brilliant metallic tints
or dull red patches when they are not wholly black, and are
therefore very conspicuous by day, when insect-eaters are
kept off by their bad odour and taste, but are sufficiently
invisible at night, when it is of importance that their prey
should not become aware of their proximity.

It seems probable that, in some cases, that which would

1 These colours may, however, be protective by causing the rolled-up insect
to look like a piece of shining stoiie or mineral.

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 53

appear at first to be a source of danger to its possessor may
really be a means of protection. Many showy and weak-
flying butterflies have a very broad expanse of wing, as in the
brilliant blue Morphos of Brazilian forests, and the large
Eastern Papilios ; yet these groups are. tolerably plentiful.
Now, specimens of these butterflies are often captured with
pierced and broken wings, as if they had been seized by birds
from whom they had escaped ; but if the wings had been
much smaller in proportion to the body, it seems probable
that the insect would be more frequently struck or pierced in
a vital part, and thus the increased expanse of the wings may
have been indirectly beneficial.

In other cases the capacity of increase in a species is so
great that however many of the perfect insect may be de-
stroyed, there is always ample means for the continuance of
the race. Many of the flesh-flies, gnats, ants, palm-tree
weevils, and locusts are in this category. The whole family
of Cetoniadse or rose chafers, so full of gaily-coloured species,
are probably saved from attack by a combination of char-
acters. They fly very rapidly with a zigzag or waving
course ; they hide themselves the moment they alight, either
in the corolla of flowers, or in rotten wood, or in cracks and
hollows of trees, and they are generally encased in a very
hard and polished coat of mail, which may render them un-
satisfactory food to such birds as would be able to capture
them. The causes which lead to the development of colour
have been here able to act unchecked, and we see the result
in a large variety of the most gorgeously-coloured insects.

Here, then, with our very imperfect knowledge of the
life-history of animals, we are able to see that there are
widely varied modes by which they may obtain protection
from their enemies or concealment from their prey. Some of
these seem to be so complete and effectual as to answer all the
wants of the race, and lead to the maintenance of the largest
possible population. When this is the case, we can well under-
stand that no further protection derived from a modification
of colour can be of the slightest use, and the most brilliant
hues may be developed without any prejudicial effect upon
the species. On some of the laws that determine the de-
velopment of colour something may be said presently. It is

54 NATURAL SELECTION in

now merely necessary to show that concealment by obscure
or imitative tints is only one out of very many ways by which
animals maintain their existence ; and having done this we
are prepared to consider the phenomena of what has been
termed "mimicry." It is to be particularly observed, how-
ever, that the word is not here used in the sense of voluntary
imitation, but to imply a particular kind of resemblance —
a resemblance not in internal structure but in external
appearance — a resemblance in those parts only that catch
the eye — a resemblance that deceives. As this kind of
resemblance has the same effect as voluntary imitation or
mimicry, and as we have no word that expresses the required
meaning, " mimicry " was adopted by Mr. Bates (who was the
first to explain the facts), and has led to some misunder-
standing; but there need be none, if it is remembered
that both " mimicry " and " imitation " are used in a meta-
phorical sense, as implying that close external likeness which
causes things unlike in structure to be mistaken for each
other.

Mimicry

It has been long known to entomologists that certain
insects bear a strange external resemblance to others belong-
ing to distinct genera, families, or even orders, and with
which they have no real affinity whatever. The fact, how-
ever, appears to have been generally considered as dependent
upon some unknown law of "analogy" — some "system of
nature," or " general plan," which had guided the Creator in
designing the myriads of insect forms, and which we could
never hope to understand. In only one case does it appear
that the resemblance was thought to be useful, and to have
been designed as a means to a definite and intelligible pur-
pose. The flies of the genus Volucella enter the nests of bees
to deposit their eggs, so that their larvae may feed upon the
larvae of the bees, and these flies are each wonderfully like
the bee on which it is parasitic. Kirby and Spence believed
that this resemblance or " mimicry " was for the express pur-
pose of protecting the flies from the attacks of the bees, and
the connection is so evident that it was hardly possible to
avoid this conclusion. The resemblance, however, of moths

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 55

to butterflies or to bees, of beetles to wasps, and of locusts to
beetles, has been many times noticed by eminent writers ;
but scarcely ever till within the last few years does it appear
to have been considered that these resemblances had any
special purpose, or were of any direct benefit to the insects
themselves. In this respect they were looked upon as
accidental, as instances of the " curious analogies " in nature
which must be wondered at but which could not be explained.
Recently, however, these instances have been greatly multi-
plied ; the nature of the resemblances has been more carefully
studied, and it has been found that they are often carried out
into such details as almost to imply a purpose of deceiving
the observer. The phenomena, moreover, have been shown
to follow certain definite laws, which again all indicate their
dependence on the more general law of the " survival of the
fittest," or, " the preservation of favoured races in the struggle
for life." It will, perhaps, be as well here to state what these
laws or general conclusions are, and then to give some account
of the facts which support them.

The first law is, that in an overwhelming majority of cases
of mimicry, the animals (or the groups) which resemble each
other inhabit the same country, the same district, and in
most cases are to be found together on the very same spot.

The second law is, that these resemblances are not indis-
criminate, but are limited to certain groups, which in every
case are abundant in species and individuals, and can often
be ascertained to have some special protection.

The third law is, that the species which resemble or
" mimic " these dominant groups are comparatively less
abundant in individuals, and are often very rare.

These laws will be found to hold good in all the cases of
true mimicry among various classes of animals to which we
have now to call the attention of our readers.

Mimicry among Lepidoptera

As it is among butterflies that instances of mimicry are
most numerous and most striking, an account of some of the
more prominent examples in this group will first be given.
There is in South America an extensive family of these
insects, the Heliconidae, which are in many respects very

56 NATURAL SELECTION f in

remarkable. They are so abundant and characteristic in
all the woody portions of the American tropics, that in
almost every locality they will be seen more frequently than
any other butterflies. They are distinguished by very elon-
gate wings, body, and antennae, and are exceedingly beautiful
and varied in their colours ; spots and patches of yellow, red,
or pure white upon a black, blue, or brown ground being
most general. They frequent the forests chiefly, and all fly
slowly and weakly ; yet although they are so conspicuous,
and could certainly be caught by insectivorous birds more
easily than almost any other insects, their great abundance
all over the wide region they inhabit shows that they are not
so persecuted. It is to be especially remarked also, that they
possess no adaptive colouring to protect them during repose,
for the under side of their wings presents the same, or at least
an equally conspicuous colouring as the upper side ; and they
may be observed after sunset suspended at the end of twigs
and leaves, where they have taken up their station for the
night, fully exposed to the attacks of enemies if they have
any. These beautiful insects possess, however, a strong
pungent semi-aromatic or medicinal odour, which seems to
pervade all the juices of their system. When the entomolo-
gist squeezes the breast of one of them between his fingers to
kill it, a yellow liquid exudes which stains the skin, and the
smell of which can only be got rid of by time and repeated
washings. Here we have probably the cause of their im-
munity from attack, since there is a great deal of evidence to
show that certain insects are so disgusting to birds that they
will under no circumstances touch them. Mr. Stainton has
observed that a brood of young turkeys greedily devoured all
the worthless moths he had amassed in a night's " sugaring,"
yet one after another seized and rejected a single white moth
which happened to be among them. Young pheasants and
partridges which eat many kinds of caterpillars seem to have
an absolute dread of that of the common currant moth, which
they will never touch, and tomtits as well as other small birds
appear never to eat the same species. In the case of the
Heliconidae, however, we have some direct evidence to the
same effect. In the Brazilian forests there are great numbers
of insectivorous birds — as jacamars, trogons, and puffbirds —

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 57

which catch insects on the wing, and that they destroy many
butterflies is indicated by the fact that the wings of these
insects are often found on the ground where their bodies
have been devoured. But among these there are no wings of
Heliconidae, while those of the large showy Nymphalidse,
which have a much swifter flight, are often met with. Again,
a gentleman who had recently returned from Brazil stated at
a meeting of the Entomological Society that he once observed
a pair of puffbirds catching butterflies, which they brought to
their nest to feed their young ; yet during half an hour they
never brought one of the Heliconidse, which were flying lazily
about in great numbers, and which they could have captured
more easily than any others. It was this circumstance that
led Mr. Belt to observe them so long, as he could not under-
stand why the most common insects should be altogether
passed by. Mr. Bates also tells us that he never saw them
molested by lizards or predacious flies, which often pounce on
other butterflies.

If, therefore, we accept it as highly probable (if not proved)
that the Heliconidse are very greatly protected from attack by
their peculiar odour and taste, we find it much more easy to
understand their chief characteristics — their great abundance,
their slow flight, their gaudy colours, and the entire absence
of protective tints on their under surfaces. This property
places them somewhat in the position of those curious wingless
birds of oceanic islands, the dodo, the apteryx, and the moas,
which are with great reason supposed to have lost the power
of flight on account of the absence of carnivorous quadrupeds.
Our butterflies have been protected in a different way, but
quite as effectually; and the result has been that as there has
been nothing to escape from, there has been no weeding out
of slow flyers, and as there has been nothing to hide from,
there has been no extermination of the bright-coloured varieties,
and no preservation of such as tended to assimilate with sur-
rounding objects.

Now let us consider how this kind of protection must act.
Tropical insectivorous birds very frequently sit on dead
branches of a lofty tree, or on those which overhang forest
paths, gazing intently around, and darting off at intervals to
seize an insect at a considerable distance, which they generally

NATURAL SELECTION

return to their station to devour. If a bird began by capturing
the slow-flying conspicuous Heliconidse, and found them always
so disagreeable that it could not eat them, it would after a
very few trials leave off catching them at all ; and their whole
appearance, form, colouring, and mode of flight are so peculiar
that there can be little doubt birds would soon learn to dis-
tinguish them at a long distance, and never waste any time in
pursuit of them. Under these circumstances, it is evident
that any other butterfly of a group which birds were accus-
tomed to devour would be almost equally well protected by
closely resembling a Heliconian externally, as if it acquired
also the disagreeable odour; always supposing that there
were only a few of them among a great number of the Heli-
conias. If the birds could not distinguish the two kinds
externally, and there were on the average only one eatable
among fifty uneatable, they would soon give up seeking for
the eatable ones, even if they knew them to exist. If, on the
other hand, any particular butterfly of an eatable group
acquired the disagreeable taste of the Heliconias while it
retained the characteristic form and colouring of its own
group, this would be really of no use to it whatever ; for the
birds would go on catching it among its eatable allies (com-
pared with which it would rarely occur), it would be wounded
and disabled, even if rejected, and its increase would thus be
as effectually checked as if it were devoured. It is important,
therefore, to understand that if any one genus of an extensive
family of eatable butterflies were in danger of extermination
from insect-eating birds, and if two kinds of variation were
going on among them, some individuals possessing a slightly
disagreeable taste, others a slight resemblance to the Heli-
conidse, this latter quality would be much more valuable than
the former. The change in flavour would not at all prevent
the variety from being captured as before, and it would
almost certainly be thoroughly disabled before being rejected.
The approach in colour and form to the Heliconidse, however,
would be at the very first a positive, though perhaps a slight
advantage ; for although at short distances this variety would
be easily distinguished and devoured, yet at a longer distance
it might be mistaken for one of the uneatable group, and so
be passed by and gain another day's life, which might in

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 59

many cases be sufficient for it to lay a quantity of eggs and
leave a numerous progeny, many of which would inherit
the peculiarity which had been the safeguard of their parent.

Now, this hypothetical case is exactly realised in South
America. Among the white butterflies forming the family
Pieridse (many of which do not greatly differ in appearance
from our own cabbage butterflies) is a genus of rather small
size (Leptalis), some species of which are white like their
allies, while the larger number exactly resemble the Heli-
conidse in the form and colouring of the wings. It must
always be remembered that these two families are as absolutely
distinguished from each other by structural characters as are
the carnivora and the ruminants among quadrupeds, and that
an entomologist can always distinguish the one from the
other by the structure of the feet, just as certainly as a
zoologist can tell a bear from a buffalo by the skull or by a
tooth. Yet the resemblance of a species of the one family to
another species in the other family was often so great, that
both Mr. Bates and myself were many times deceived at the
time of capture, and did not discover the distinctness of the
two insects till a closer examination detected their essential
differences. During his residence of eleven years in the
Amazon valley, Mr. Bates found a number of species or
varieties of Leptalis, each of which was a more or less exact
copy of one of the Heliconidse of the district it inhabited ;
and the results of his observations are embodied in a paper
published in the Linncean Transactions, in which he first ex-
plained the phenomena of " mimicry " as the result of natural
selection, and showed its identity in cause and purpose with
protective resemblance to vegetable or inorganic forms.

The imitation of the Heliconidae by the Leptalides is
carried out to a wonderful degree in form as well as in
colouring. The wings have become elongated to the same
extent, and the antennae and abdomen have both become
lengthened, to correspond with the unusual condition in
which they exist in the former family. In coloration there
are several types in the different genera of Heliconidae. The
genus Mechanitis is generally of a rich semi-transparent
brown, banded with black and yellow ; Methona is of large
size, the wings transparent like horn, and with black trans-

NATURAL SELECTION

verse bands ; while the delicate Ithomias are all more or less
transparent, with black veins and borders, and often with
marginal and transverse bands of orange red. These different
forms are all copied by the various species of Leptalis, every
band and spot and tint of colour, and the various degrees of
transparency, being exactly reproduced. As if to derive all
the benefit possible from this protective mimicry, the habits
have become so modified that the Leptalides generally
frequent the very same spots as their models, and have the
same mode of flight ; and as they are always very scarce
(Mr. Bates estimating their numbers at about one to a
thousand of the group they resemble), there is hardly a
possibility of their being found out by their enemies. It is
also very remarkable that in almost every case the particular
Ithomias and other species of Heliconidse which they resemble
are noted as being very common species, swarming in indi-
viduals, and found over a wide range of country. This
indicates antiquity and permanence in the species, and is
exactly the condition most essential both to aid in the
development of the resemblance and to increase its utility.

But the Leptalides are not the only insects who have
prolonged their existence by imitating the great protected
group of Heliconidse; — a genus of quite another family of
most lovely small American butterflies, the Erycinidse, and
three genera of diurnal moths, also present species which
often mimic the same dominant forms, so that some, as
Ithomia ilerdina of St. Paulo, for instance, have flying with
them a few individuals of three widely different insects,
which are yet disguised with exactly the same form, colour,
and markings, so as to be quite undistinguishable when upon
the wing. Again, the Heliconidse are not the only group
that are imitated, although they are the most frequent models.
The black and red group of South American Papilios, and
the handsome Erycinian genus Stalachtis, have also a few
who copy them ; but this fact offers no difficulty, since these
two groups are almost as dominant as the Heliconidse. They
both fly very slowly, they are both conspicuously coloured,
and they both abound in individuals ; so that there is every
reason to believe that they possess a protection of a similar
kind to the Heliconidae, and that it is therefore equally an

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 61

advantage to other insects to be mistaken for them. There
is also another extraordinary fact that we are not yet in a
position clearly to comprehend : some groups of the Heli-
conidae themselves mimic other groups. Species of Heliconia
mimic Mechanitis, and every species of Napeogenes mimics
some other Heliconideous butterfly.1 This would seem to
indicate that the distasteful secretion is not produced alike
by all members of the family, and that where it is deficient
protective imitation comes into play. It is this, perhaps,
that has caused such a general resemblance among the Heli-
conidse, such a uniformity of type with great diversity of
colouring, since any aberration causing an insect to cease to
look like one of the family would inevitably lead to its being
attacked, wounded, and exterminated, even although it was
not eatable.

In other parts of the world an exactly parallel series of
facts have been observed. The Danaidse and the Acrseidse of
the Old World tropics form in fact one great group with the
Heliconidse. They have the same general form, structure,
and habits ; they possess the same protective odour, and are
equally abundant in individuals, although not so varied in
colour, blue and white spots on a black ground being the
most general pattern. The insects which mimic these are
chiefly Papilios and Diadema, a genus allied to our peacock
and tortoiseshell butterflies. In tropical Africa there is a
peculiar group of the genus Danais, characterised by dark-
brown and bluish-white colours, arranged in bands or stripes.
One of these, Danais niavius, is exactly imitated both by
Papilio hippocoon and by Diadema anthedon ; another, Danais
echeria, by Papilio cenea ; and in Natal a variety of the
Danais is found having a white spot at the tip of wings,
accompanied by a variety of the Papilio bearing a correspond-
ing white spot. Acrsea gea is copied in its very peculiar
style of coloration by the female of Papilio cynorta, by
Panopsea hirce, and by the female of Elymnias phegea. Acraea
euryta of Calabar has a female variety of Panopea hirce from
the same place which exactly copies it ; and Mr. Trimen, in
his paper on " Mimetic Analogies among African Butterflies,"

1 A satisfactory explanation of this phenomenon has now been found. See
Darwinism, p. 252.

NATURAL SELECTION

published in the Transactions of the Linncean Society for 1868,
gives a list of no less than sixteen species and varieties of
Diadema and its allies, and ten of Papilio, which in their
colour and markings are perfect mimics of species or varieties
of Danais or Acrsea which inhabit the same districts.

Passing on to India, we have Danais tytia, a butterfly
with semi-transparent bluish wings and a border of rich
reddish brown. This remarkable style of colouring is exactly
reproduced in Papilio agestor and in Diadema nama, and all
three insects not unfrequently come together in collections
made at Darjeeling. In the Philippine Islands the large and
curious Idea leuconoe, with its semi-transparent white wings,
veined and spotted with black, is copied by the rare Papilio
idseoides from the same islands.

In the Malay archipelago the very common and beautiful
Euplsea midamus is so exactly mimicked by two rare Papilios
(P. paradoxa and P. senigma) that I generally caught them
under the impression that they were the more common
species ; and the equally common and even more beautiful
Euplsea rhadamanthus, with its pure white bands and spots
on a ground of glossy blue and black, is reproduced in the
Papilio caunus. Here also there are species of Diadema
imitating the same group in two or three instances ; but we
shall have to adduce these further on in connection with
another branch of the subject.

It has been already mentioned that in South America
there is a group of Papilios which have all the characteristics
of a protected race, and whose peculiar colours and markings
are imitated by other butterflies not so protected. There is
just such a group also in the East, having very similar
colours and the same habits, and these also are mimicked by
other species in the same genus not closely allied to them,
and also by a few of other families. Papilio hector, a
common Indian butterfly of a rich black colour spotted with
crimson, is so closely copied by Papilio romulus that the
latter insect has been thought to be its female. A close
examination shows, however, that it is essentially different,
and belongs to another section of the genus. Papilio
antiphus and P. diphilus, black swallow-tailed butterflies with
cream-coloured spots, are so well imitated by varieties of P.

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 63

theseus, that several writers have classed them as the same
species. Papilio liris, found only in the island of Timor, is
accompanied there by P. aenomaus, the female of which so
exactly resembles it that they can hardly be separated in the
cabinet, and on the wing are quite undistinguishable. But
one of the most curious cases is the fine yellow -spotted
Papilio coon, which is unmistakably imitated by the female
tailed form of Papilio memnon. These are both from
Sumatra ; but in North India P. coon is replaced by another
species, which has been named P. doubledayi, having red
spots instead of yellow ; and in the same district the corre-
sponding female tailed form of Papilio androgeus, sometimes
considered a variety of P. memnon, is similarly red-spotted.
Mr. Westwood has described some curious day-flying moths
(Epicopeia) from North India, which have the form and colour
of Papilios of this section, and two of these are very good
imitations of Papilio polydorus and Papilio varuna, also from
North India.

Almost all these cases of mimicry are from the tropics,
where the forms of life are more abundant, and where insect
development especially is of unchecked luxuriance ; but there
are also one or two instances in temperate regions. In North
America, the large and handsome red and black butterfly
Danais Archippus is very common ; and the same country is
inhabited by Limenitis Misippus, which closely resembles the
Danais, while it differs entirely from every species of its own
genus.

The only case of probable mimicry in our own country
is that of the common white moth (Spilosoma menthastri),
referred to at p. 56 as being rejected by young turkeys
among hundreds of other moths on which they greedily
fed. Each bird in succession took hold of this moth and
threw it down again, as if too nasty to eat. Mr. Jenner
Weir also found that this moth was refused by the Bullfinch,
Chaffinch, Yellow Hammer, and Red Bunting, but eaten after
much hesitation by the Robin. We may therefore fairly con-
clude that this species would be disagreeable to many other
birds, and would thus have an immunity from attack, which
may be the cause of its great abundance and of its conspicu-
ous white colour. Now it is a curious thing that there is

64 NATURAL SELECTION in

another moth, Diaphora mendica, which appears about the
same time, and whose female only is white. It is about the
same size as Spilosoma menthastri, and sufficiently resembles
it in the dusk, and this moth is much less common. It seems
very probable, therefore, that these species stand in the same
relation to each other as the mimicking butterflies of various
families do to the Heliconidse and Danaidse. It would be very
interesting to experiment on all white moths, to ascertain if
those which are most common are generally rejected by birds.
It may be anticipated that they would be so, because white
is the most conspicuous of all colours for nocturnal insects,
and had they not some other protection would certainly be
very injurious to them.

Lepidoptera mimicking other Insects

In the preceding cases we have found Lepidoptera imitat-
ing other species of the same order, and such species only as
we have good reason to believe were free from the attacks of
many insectivorous creatures ; but there are other instances
in which they altogether lose the external appearance of the
order to which they belong, and take on the dress of bees or
wasps — insects which have an undeniable protection in their
stings. The Sesiidas and ^geriidse, two families of day-flying
moths, are particularly remarkable in this respect, and a mere
inspection of the names given to the various species shows
how the resemblance has struck every one. We have api-
formis, vespiforme, ichneumoniforme, scoliseforme, sphegi-
forme (bee -like, wasp -like, ichneumon -like, etc.), and many
others, all indicating a resemblance to stinging Hymenoptera.
In Britain we may particularly notice Sesia bombiliformis,
which very closely resembles the male of the large and
common humble bee, Bombus hortorum; Sphecia craboni-
forme, which is coloured like a hornet, and is (on the
authority of Mr. Jenner Weir) much more like it when alive
than when in the cabinet, from the way in which it carries its
wings; and the currant clear- wing, Trochilium tipuliforme,
which resembles a small black wasp (Odynerus sinuatus) very
abundant in gardens at the same season. It has been so
much the practice to look upon these resemblances as mere
curious analogies playing no part in the economy of nature,

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 65

that we have scarcely any observations of the habits and
appearance when alive of the hundreds of species of these
groups in various parts of the world, or how far they are
accompanied by Hymenoptera, which they specifically re-
semble. There are many species in India (like those figured
by Professor Westwood in his Oriental Entomology) which
have the hind legs very broad and densely hairy, so as
exactly to imitate the brush-legged bees (Scopulipedes) which
abound in the same country. In this case we have more
than mere resemblance of colour, for that which is an import-
ant functional structure in the one group is imitated in
another whose habits render it perfectly useless.

Mimicry among Beetles

It may fairly be expected that if these imitations of one
creature by another really serve as a protection to weak and
decaying species, instances of the same kind will be found
among other groups than the Lepidoptera; and such is the case,
although they are seldom so prominent and so easily recognised
as those already pointed out as occurring in that order. A few
very interesting examples may, however, be pointed out in most
of the other orders of insects. The Coleoptera or beetles that
imitate other Coleoptera of distinct groups are very numerous in
tropical countries, and they generally follow the laws already
laid down as regulating these phenomena. The insects which
others imitate always have a special protection, which leads
them to be avoided as dangerous or uneatable by small
insectivorous animals ; some have a disgusting taste (analogous
to that of the Heliconidse) ; others have such a hard and
stony covering that they cannot be crushed or digested;
while a third set are very active, and armed with powerful
jaws, as well as having some disagreeable secretion. Some
species of Eumorphidse and Hispidse, small flat or hemispher-
ical beetles which are exceedingly abundant, and have a dis-
agreeable secretion, are imitated by others of the very
distinct group of Longicornes (of which our common musk-
beetle may be taken as an example). The extraordinary
little Cyclopeplus batesii belongs to the same sub-family of
this group as the Onychocerus scorpio and O. concentricus,
which have already been adduced as imitating with such
F

NATURAL SELECTION

wonderful accuracy the bark of the trees they habitually fre-
quent; but it differs totally in outward appearance from
every one of its allies, having taken upon itself the exact
shape and colouring of a globular Corynomalus, a little stink-
ing beetle with clubbed antennae. It is curious to see how
these clubbed antennae are imitated by an insect belonging to
a group with long slender antennas. The sub-family Aniso-
cerinae, to which Cyclopeplus belongs, is characterised by all
its members possessing a little knob or dilatation about the
middle of the antennse. This knob is considerably enlarged
in C. batesii, and the terminal portion of the antennas beyond
it is so small and slender as to be scarcely visible, and thus
an excellent substitute is obtained for the short clubbed
antennae of the Corynomalus. Erythroplatis corallifer is
another curious broad flat beetle, that no one would take for
a Longicorn, since it almost exactly resembles Cephalodonta
spinipes, one of the commonest of the South American
Hispidse ; and what is still more remarkable, another Longi-
corn of a distinct group, Streptolabis hispoides, was found
by Mr. Bates, which resembles the same insect with equal
minuteness, — a case exactly parallel to that among butterflies,
where species of two or three distinct groups mimicked the
same Heliconia. Many of the soft- winged beetles (Malaco-
derms) are excessively abundant in individuals, and it is
probable that they have some similar protection, more
especially as other species often strikingly resemble them. A
Longicorn beetle, Paeciloderma terminale, found in Jamaica, is
coloured exactly in the same way as a Lycus (one of the
Malacoderms) from the same island. Eroschema poweri, a
Longicorn from Australia, might certainly be taken for one of
the same group, and several species from the Malay Islands
are equally deceptive. In the Island of Celebes I found one
of this group, having the whole body and elytra of a rich
deep blue colour, with the head only orange; and in company
with it an insect of a totally different family (Eucnemidae)
with identically the same coloration, and of so nearly the
same size ' and form as to completely puzzle the collector on
every fresh occasion of capturing them. I have been recently
informed by Mr. Jenner Weir, who keeps a variety of small
birds, that none of them will touch our common "soldiers

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 67

and sailors" (species of Malacoderms), thus confirming my
belief that they were a protected group, founded on the fact
of their being at once very abundant, of conspicuous colours,
and the objects of mimicry.

There are a number of the larger tropical weevils which
have the elytra and the whole covering of the body so hard
as to be a great annoyance to the entomologist, because in
attempting to transfix them the points of his pins are con-
stantly turned. I have found it necessary in these cases to
drill a hole very carefully with the point of a sharp penknife
before attempting to insert a pin. Many of the fine long-
antennsed Anthribidse (an allied group) have to be treated in
the same way. We can easily understand that after small
birds have in vain attempted to eat these insects, they should
get to know them by sight, and ever after leave them alone,
and it will then be an advantage for other insects which are
comparatively soft and eatable to be mistaken for them. We
need not be surprised, therefore, to find that there are many
Longicorns which strikingly resemble the " hard beetles " of
their own district. In South Brazil, Acanthotritus dorsalis is
strikingly like a Curculio of the hard genus Heiliplus, and
Mr. Bates assures me that he found Gymnocerus cratoso-
moides (a Longicorn) on the same tree with a hard Crato-
somus (a weevil), which it exactly mimics. Again, the pretty
Longicorn, Phacellocera batesii, mimics one of the hard
Anthribidae of the genus Ptychoderes, having long slender
antennae. In the Moluccas we find Cacia anthriboides, a
small Longicorn which might be easily mistaken for a very
common species of Anthribidse found in the same districts ;
and the very rare Capnolymma stygium closely imitates the
common Mecocerus gazella, which abounded where it was
taken. Doliops curculionoides and other allied Longicorns
from the Philippine Islands most curiously resemble, both in
form and colouring, the brilliant Pachyrhynchi, — Curculi-
onidse, which are almost peculiar to that group of islands. The
remaining family of Coleoptera most frequently imitated is
the Cicindelidse. The rare and curious Longicorn, Collyrodes
lacordairei, has exactly the form and colouring of the genus
Collyris, while an undescribed species of Heteromera is
exactly like a Therates, and was taken running on the trunks

NATURAL SELECTION

of trees, as is the habit of that group. There is one curious
example of a Longicorn mimicking a Longicorn, like the
Papilios and Heliconidae which mimic their own allies. Agnia
fasciata, belonging to the sub-family Hypselominse, and
Nemophas grayi, belonging to the Lamiinse, were taken in
Amboyna on the same fallen tree at the same time, and were
supposed to be the same species till they were more carefully
examined, and found to be structurally quite different. The
colouring of these insects is very remarkable, being rich steel-
blue black, crossed by broad hairy bands of orange buff, and
out of the many thousands of known species of Longicorns
they are probably the only two which are so coloured. The
Nemophas grayi is the larger, stronger, and better armed
insect, and belongs to a more widely spread and dominant
group, very rich in species and individuals, and is therefore
most probably the subject of mimicry by the other species.

Beetles mimicking other Insects

We will now adduce a few cases in which beetles imitate
other insects, and insects of other orders imitate beetles.

Charis melipona, a South American Longicorn of the
family Necydalidse, has been so named from its resemblance
to a small bee of the genus Melipona. It is one of the most
remarkable cases of mimicry, since the beetle has the thorax
and body densely hairy like the bee, and the legs are tufted
in a manner most unusual in the order Coleoptera. Another
Longicorn, Odontocera odyneroides, has the abdomen banded
with yellow, and constricted at the base, and is altogether so
exactly like a small common wasp of the genus Odynerus,
that Mr. Bates informs us he was afraid to take it out
of his net with his fingers for fear of being stung. Had
Mr. Bates' taste for insects been less omnivorous than it
was, the beetle's disguise might have saved it from his pin, as
it had no doubt often done from the beak of hungry birds.
A larger insect, Sphecomorpha chalybea, is exactly like one
of the large metallic blue wasps, and like them has the
abdomen connected with the thorax by a pedicel, rendering
the deception most complete and striking. Many Eastern
species of Longicorns of the genus Oberea, when on the wing,
exactly resemble Tenthredinidse, and many of the small

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 69

species of Hesthesis run about on timber, and cannot be dis-
tinguished from ants. There is one genus of South American
Longicorns that appears to mimic the shielded bugs of the
genus Scutellera. The Gymnocerus capucinus is one of
these, and is very like Pachyotris fabricii, one of the
Scutelleridee. The beautiful Gymnocerus dulcissimus is also
very like the same group of insects, though there is no
known species that exactly corresponds to it ; but this is not
to be wondered at, as the tropical Hemiptera have been com-
paratively so little cared for by collectors.

Insects mimicking Species of other Orders
The most remarkable case of an insect of another order
mimicking a beetle is that of the Condylodera tricondyloides,
one of the cricket family from the Philippine Islands, which
is so exactly like a Tricondyla (one of the tiger beetles) that
such an experienced entomologist as Professor Westwood
placed it among them in his cabinet, and retained it there
a long time before he discovered his mistake ! Both insects
run along the trunks of trees, and whereas Tricondylas are
very plentiful, the insect that mimics it is, as in all other
cases, very rare. Mr. Bates also informs us that he found at
Santarem, on the Amazon, a species of locust which mimicked
one of the tiger beetles of the genus Odontocheila, and was
found on the same trees which they frequented.

There are a considerable number of Diptera, or two- winged
flies, that closely resemble wasps and bees, and no doubt
derive much benefit from the wholesome dread which those
insects excite. The Midas dives, and other species of large
Brazilian flies, have dark wings and metallic blue elongate
bodies, resembling the large stinging Sphegidse of the same
country ; and a very large fly of the genus Asilus has black-
banded wings and the abdomen tipped with rich orange, so as
exactly to resemble the fine bee Euglossa dimidiata, and both
are found in the same parts of South America. We have
also in our own country species of Bombylius which are
almost exactly like bees. In these cases the end gained by
the mimicry is no doubt freedom from attack, but it has some-
times an altogether different purpose. There are a number of
parasitic flies whos,e larvae feed upon the larvae of bees, such

70 NATURAL SELECTION in

as the British genus Volucella and many of the tropical
Bombylii, and most of these are exactly like the particular
species of bee they prey upon, so that they can enter their
nests unsuspected to deposit their eggs. There are also bees
that mimic bees. The cuckoo bees of the genus Nomada are
parasitic on the Andrenidse, and they resemble either wasps
or species of Andrena ; and the parasitic humble bees of the
genus Apathus almost exactly resemble the species of humble
bees in whose nests they are reared. Mr. Bates informs us
that he found numbers of these " cuckoo " bees and flies on
the Amazon, which all wore the livery of working bees
peculiar to the same country.

There is a genus of small spiders in the tropics which feed
on ants, and they are exactly like ants themselves, which no
doubt gives them more opportunity of seizing their prey ; and
Mr. Bates found on the Amazon a species of Mantis which
exactly resembled the white ants which it fed upon, as well
as several species of crickets (Scaphura), which resembled in
a wonderful manner different sand-wasps of large size, which
are constantly on the search for crickets with which to
provision their nests.

Perhaps the most wonderful case of all is the large cater-
pillar mentioned by Mr. Bates, which startled him by its
close resemblance to a small snake. The first three segments
behind the head were dilatable at the will of the insect, and
had on each side a large black pupillated spot, which re-
sembled the eye of the reptile. Moreover, it resembled a
poisonous viper, not a harmless species of snake, as was
proved by the imitation of keeled scales on the crown produced
by the recumbent feet, as the caterpillar threw itself backward !

The attitudes of many of the tropical spiders are most
extraordinary and deceptive, but little attention has been
paid to them. They often mimic other insects, and some,
Mr. Bates assures us, are exactly like flower buds, and take
their station in the axils of leaves, where they remain motion-
less waiting for their prey.

Cases of Mimicry among the Fertebrata

Having thus shown how varied and extraordinary are the
modes in which mimicry occurs among insects, we have now

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 71

to inquire if anything of the same kind is to be observed
among vertebrated animals. When we consider all the
conditions necessary to produce a good deceptive imitation,
we shall see at once that such can very rarely occur in the
higher animals, since they possess none of those facilities for
the almost infinite modifications of external form which exist
in the very nature of insect organisation. The outer covering
of insects being more or less solid and horny, they are capable
of almost any amount of change of form and appearance with-
out any essential modification internally. In many groups
the wings give much of the character, and these organs may
be much modified both in form and colour without interfering
with their special functions. Again, the number of species of
insects is so great, and there is such diversity of form and
proportion in every group, that the chances of an accidental
approximation in size, form, and colour of one insect to
another of a different group are very considerable ; and it is
these chance approximations that furnish the basis of mimicry,
to be continually advanced and perfected by the survival of
those varieties only which tend in the right direction.

In the Vertebrata, on the contrary, the skeleton being
internal, the external form depends almost entirely on the
proportions and arrangement of that skeleton, which again is
strictly adapted to the functions necessary for the well-being
of the animal. The form cannot, therefore, be rapidly modified
by variation, and the thin and flexible integument will not
admit of the development of such strange protuberances as
occur continually in insects. The number of species of each
group in the same country is also comparatively small, and
thus the chances of that first accidental resemblance which
is necessary for natural selection to work upon are much
diminished. We can hardly see the possibility of a mimicry
by which the elk could escape from the wolf, or the buffalo
from the tiger. There is, however, in one group of Verte-
brata such a general similarity of form, that a very slight
modification, if accompanied by identity of colour, would
produce the necessary amount of resemblance ; and at the
same time there exist a number of species which it would be
advantageous for others to resemble, since they are armed
with the most fatal weapons of offence. We accordingly find

72 NATURAL SELECTION in

that reptiles furnish us with a very remarkable and instructive
case of true mimicry.

Mimicry among Snakes

There are in tropical America a number of venomous
snakes of the genus Elaps, which are ornamented with brilliant
colours disposed in a peculiar manner. The ground colour is
generally bright red, on which are black bands of various
widths and sometimes divided into two or three by yelloAv
rings. Now, in the same country are found several genera of
harmless snakes, having no affinity whatever with the above,
but coloured exactly the same. For example, the poisonous
Elaps fulvius often occurs in Guatemala with simple black
bands on a coral-red ground; and in the same country is
found the harmless snake Pliocerus equalis, coloured and
banded in identically the same manner. A variety of Elaps
corallinus has the black bands narrowly bordered with yellow
on the same red ground colour, and a harmless snake, Homa-
locranium semi-cinctum (Colubridae), has exactly the same
markings, and both are found in Mexico. The deadly Elaps
lemniscatus has the black bands very broad, and each of them
divided into three by narrow yellow rings ; and this again is
exactly copied by a harmless snake, Pliocerus elapoides, which
is found along with its model in Mexico.

But, more remarkable still, there is in South America a
third group of snakes, the genus Oxyrhopus (Scytalidse),
doubtfully venomous, and having no immediate affinity with
either of the preceding, which has also the same curious
distribution of colours, namely, variously disposed rings of
red, yellow, and black ; and there are some cases in which
species of all three of these groups similarly marked inhabit
the same district. For example, Elaps mipartitus has single
black rings very close together. It inhabits the west side of
the Andes, and in the same districts occur Pliocerus eury-
zonus and Oxyrhopus petolarius, which exactly copy its
pattern. In Brazil Elaps lemniscatus is copied by Oxyrhopus
trigeminus, both having black rings disposed in threes. In
Elaps hemiprichii the ground colour appears to be black, with
alternations of two narrow yellow bands and a broader red
one ; and of this pattern again we have an exact double in

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 73

Oxyrhopus formosus, both being found in many localities of
tropical South America.

What adds much to the extraordinary character of these
resemblances is the fact, that nowhere in the world but in
America are there any snakes which have this style of
colouring. Dr. Gunther, of the British Museum, who has
kindly furnished some of the details here referred to, assures
me that this is the case ; and that red, black, and yellow rings
occur together on no other snakes in the world but on Elaps
and the species which so closely resemble it. In all these
cases, the size and form as well as the coloration are so
much alike, that none but a naturalist would distinguish the
harmless from the poisonous species.

Many of the small tree-frogs are no doubt also mimickers.
When seen in their natural attitudes, I have been often unable
to distinguish them from beetles or other insects sitting upon
leaves, but regret to say I neglected to observe what species
or groups they most resembled, and the subject does not yet
seem to have attracted the attention of naturalists abroad.

Mimicry among Birds

In the class of birds there are a number of cases that make
some approach to mimicry, such as the resemblance of the
cuckoos, a weak and defenceless group of birds, to hawks and
Gallinacese. There is, however, one example which goes much
further than this, and seems to be of exactly the same nature
as the many cases of insect mimicry which have been already
given. In Australia and the Moluccas there is a genus of
honeysuckers called Tropidorhynchus, good sized birds, very
strong and active, having powerful grasping claws and long,
curved, sharp beaks. They assemble together in groups and
small flocks, and they have a very loud bawling note, which
can be heard at a great distance, and serves to collect a
number together in time of danger. They are very plentiful
and very pugnacious, frequently driving away crows, and
even hawks, which perch on a tree where a few of them are
assembled. They are all of rather dull and obscure colours.
Now in the same countries there is a group of orioles, forming
the sub-genus Mimeta, much weaker birds, which have lost
the gay colouring of their allies, the golden orioles, being

74 NATURAL SELECTION in

usually olive-green or brown ; and in several cases these most
curiously resemble the Tropidorhynchus of the same island.
For example, in the island of Bouru is found the Tropido-
rhynchus bouruensis, of a dull earthy colour, and the Mimeta
bouruensis, which resembles it in the following particulars :
The upper and under surfaces of the two birds are exactly of
the same tints of dark and light brown ; the Tropidorhynchus
has a large, bare black patch round the eyes ; this is copied
in the Mimeta by a patch of black feathers. The top of
the head of the Tropidorhynchus has a scaly appearance, from
the narrow scale-formed feathers, which are imitated by the
broader feathers of the Mimeta having a dusky line down
each. The Tropidorhynchus has a pale ruff formed of curious
recurved feathers on the nape (which has given the whole genus
the name of Friar birds) ; this is represented in the Mimeta
by a pale band in the same position. Lastly, the bill of the
Tropidorhynchus is raised into a protuberant keel at the base,
and the Mimeta has the same character, although it is not a
common one in the genus. The result is, that on a super-
ficial examination the birds are identical, although they have
important structural differences, and cannot be placed near
each other in any natural arrangement. As a proof that the
resemblance is really deceptive, it may be mentioned that the
Mimeta is figured and described as a honeysucker in the costly
Voyage de I' Astrolabe, under the name of Philedon bouruensis !
Passing to the island of Ceram, we find allied species of
both genera. The Tropidorhynchus subcornutus is of an earthy
brown colour washed with yellow ochre, with bare orbits,
dusky cheeks, and the usual pale recurved nape-ruff. The
Mimeta forsteni is absolutely identical in the tints of every
part of the body, the details of which are imitated in the
same manner as in the Bouru birds already described. In
two other islands there is an approximation towards mimicry,
although it is not so perfect as in the two preceding cases.
In Timor the Tropidorhynchus timoriensis is of the usual
earthy brown above, with the nape-ruff very prominent, the
cheeks black, the throat nearly white, and the whole under
surface pale whitish brown. These various tints are all well
reproduced in Mimeta virescens, the chief want of exact imita-
tion being that the throat and breast of the Tropidorhynchus

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 75

has a very scaly appearance, being covered with rigid pointed
feathers which are not imitated in the Mimeta, although there
are signs of faint dusky spots which may easily furnish the
groundwork of a more exact imitation by the continued
survival of favourable variations in the same direction.
There is also a large knob at the base of the bill of the
Tropidorhynchus which is not at all imitated by the Mimeta.
In the island of Morty (north of Gilolo) there exists the
Tropidorhynchus fuscicapillus, of a dark sooty brown colour,
especially on the head, while the under parts are rather
lighter, and the characteristic ruff of the nape is wanting.
Now it is curious that in the adjacent island of Gilolo should
be found the Mimeta phseochromus, the upper surface of
which is of exactly the same dark sooty tint as the Tropido-
rhynchus, and is the only known species that is of such a dark
colour. The under side is not quite light enough, but it is a
good approximation. This Mimeta is a rare bird, and may
very probably exist in Morty, though not yet found there ;
or, on the other hand, recent changes in physical geography
may have led to the restriction of the Tropidorhynchus to
that island, where it is very common.

Here, then, we have two cases of perfect mimicry and two
others of good approximation, occurring between species of
the same two genera of birds ; and in three of these cases the
pairs that resemble each other are found together in the same
island, and to which they are peculiar. In all these cases the
Tropidorhynchus is rather larger than the Mimeta, but the
difference is not beyond the limits of variation in species, and
the two genera are somewhat alike in form and proportion.
There are, no doubt, some special enemies by which many
small birds are attacked, but which are afraid of the Tropido-
rhynchus (probably some of the hawks), and thus it becomes
advantageous for the weak Mimeta to resemble the strong,
pugnacious, noisy, and very abundant Tropidorhynchus.

My friend, Mr. Osbert Salvin, has given me another in-
teresting case of bird mimicry. In the neighbourhood of Rio
Janeiro is found an insect-eating hawk (Harpagus diodon),
and in the same district a bird-eating hawk (Accipiter pileatus)
which closely resembles it. Both are of the same ashy tint
beneath, with the thighs and under wing -coverts reddish

76 NATURAL SELECTION in

brown, so that when on the wing and seen from below they
are undistinguishable. The curious point, however, is that
the Accipiter has a much wider range than the Harpagus,
and in the regions where the insect-eating species is not found
it no longer resembles it, the under wing-coverts varying to
white ; thus indicating that the red-brown colour is kept true
by its being useful to the Accipiter to be mistaken for the
insect-eating species, which birds have learnt not to be afraid of.

Mimicry among Mammals

Among the Mammalia the only case which may be true
mimicry is that of the insectivorous genus Cladobates, found
in the Malay countries, several species of which very closely
resemble squirrels. The size is about the same, the long
bushy tail is carried in the same way, and the colours are
very similar. In this case the use of the resemblance must
be to enable the Cladobates to approach the insects or small
birds on which it feeds under the disguise of the harmless
fruit-eating squirrel

Objections to Mr. Bates' Theory of Mimicry

Having now completed our survey of the most prominent
and remarkable cases of mimicry that have yet been noticed,
we must say something of the objections that have been made
to the theory of then- production given by Mr. Bates, and
which we have endeavoured to illustrate and enforce in the
preceding pages. Three counter explanations have been pro-
posed. Professor Westwood admits the fact of the mimicry
and its probable use to the insect, but maintains that each
species was created a mimic for the purpose of the protection
thus afforded it. Mr. Andrew Murray, in his paper on the
" Disguises of Nature," inclines to the opinion that similar
conditions of food and of surrounding circumstances have
acted in some unknown way to produce the resemblances ;
and when the subject was discussed before the Entomological
Society of London, a third objection was added — that heredity
or the reversion to ancestral types of form and coloration
might have produced many of the cases of mimicry.

Against the special creation of mimicking species there are
all the objections and difficulties in the way of special creation

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 77

in other cases, with the addition of a few that are peculiar to
it. The most obvious is, that we have gradations of mimicry
and of protective resemblance — a fact which is strongly
suggestive of a natural process having been at work. Another
very serious objection is, that as mimicry has been shown to
be useful only to those species and groups which are rare and
probably dying out, and. would cease to have any effect should
the proportionate abundance of the two species be reversed,
it follows that on the special-creation theory the one species
must have been created plentiful, the other rare ; and, not-
withstanding the many causes that continually tend to alter
the proportions of species, these two species must have always
been specially maintained at their respective proportions, or
the very purpose for which they each received their peculiar
characteristics would have completely failed. A third diffi-
culty is, that although it is very easy to understand how
mimicry may be brought about by variation and the survival
of the fittest, it seems a very strange thing for a Creator to
protect an animal by making it imitate another, when the
very assumption of a Creator implies his power to create it
so as to require no such circuitous protection. These appear
to be fatal objections to the application of the special-creation
theory to this particular case.

The other two supposed explanations, which may be
shortly expressed as the theories of " similar conditions " and
of " heredity," agree in making mimicry, where it exists, an
adventitious circumstance not necessarily connected with the
well-being of the mimicking species. But several of the most
striking and most constant facts which have been adduced
directly contradict both these hypotheses. The law that
mimicry is confined to a few groups only is one of these, for
" similar conditions " must act more or less on all groups in a
limited region, and "heredity" must influence all groups
related to each other in an equal degree. Again, the general
fact that those species which mimic others are rare, while
those which are imitated are abundant, is in no way explained
by either of these theories, any more than is the frequent
occurrence of some papable mode of protection in the imitated
species. " Reversion to an ancestral type " no way explains
why the imitator and the imitated always inhabit the very

78 NATURAL SELECTION in

same district, whereas allied forms of every degree of nearness
and remoteness generally inhabit different countries, and
often different quarters of the globe ; and neither it nor
"similar conditions" will account for the likeness between
species of distinct groups being superficial only — a disguise,
not a true resemblance ; for the imitation of bark, of leaves,
of sticks, of dung ; for the resemblance between species in
different orders, and even different classes and sub-kingdoms ;
and finally, for the graduated series of the phenomena,
beginning with a general harmony and adaptation of tint in
autumn and winter moths and in arctic and desert animals,
and ending with those complete cases of detailed mimicry
which not only deceive predacious animals, but puzzle the
most experienced insect collectors and the most learned
entomologists.

Mimicry by Female Insects only

But there is yet another series of phenomena connected
with this subject, which considerably strengthens the view
here adopted, while it seems quite incompatible with either
of the other hypotheses; namely, the relation of protective
colouring and mimicry to the sexual differences of animals.
It will be clear to every one that if two animals, which as
regards " external conditions " and " hereditary descent " are
exactly alike, yet differ remarkably in coloration, one
resembling a protected species and the other not, the resem-
blance that exists in one only can hardly be imputed to the
influence of external conditions or as the effect of heredity.
And if, further, it can be proved that the one requires
protection more than the other, and that in several cases it is
that one which mimics the protected species, while the one
that least requires protection never does so, it will afford
very strong corroborative evidence that there is a real con-
nection between the necessity for protection and the pheno-
menon of mimicry. Now the sexes of insects offer us a test
of the nature here indicated, and appear to furnish one of
the most conclusive arguments in favour of the theory that
the phenomena termed " mimicry " are produced by natural
selection.

The comparative importance of the sexes varies much in

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 79

different classes of animals. In the higher vertebrates, where
the number of young produced at a birth is small and the
same individuals breed many years in succession, the preserva-
tion of both sexes is almost equally important. In all the
numerous cases in which the male protects the female and
her offspring, or helps to supply them with food, his im-
portance in the economy of nature is proportionately increased,
though it is never perhaps quite equal to that of the female.
In insects the case is very different ; they pair but once in
their lives, and the prolonged existence of the male is in most
cases quite unnecessary for the continuance of the race. The
female, however, must continue to exist long enough to
deposit her eggs in a place adapted for the development and
growth of the progeny. Hence there is a wide difference in
the need for protection in the two sexes ; and we should,
therefore, expect to find that in some cases the special
protection given to the female was in the male less in amount
or altogether wanting. The facts entirely confirm this
expectation. In the spectre insects (Phasmidse) it is often
the females alone that so strikingly resemble leaves, while
the males show only a rude approximation. The male
Diadema misippus is a very handsome and conspicuous
butterfly, without a sign of protective or imitative colouring,
while the female is entirely unlike her partner, and is one of
the most wonderful cases of mimicry on record, resembling
most accurately the common Danais chrysippus, in whose
company it is often found. So in several species of South
American Pieris, the males are white and black, of a similar
type of colouring to our own " cabbage " butterflies, while the
females are rich yellow and buff, spotted and marked so as
exactly to resemble species of Heliconidse, with which they
associate in the forest. In the Malay archipelago is found
a Diadema which had always been considered a male insect on
account of its glossy metallic-blue tints, while its companion
of sober brown was looked upon as the female. I discovered,
however, that the reverse is the case, and that the rich and
glossy colours of the female are imitative and protective,
since they cause her exactly to resemble the common Euploea
midamus of the same regions, a species which has been
already mentioned in this essay as mimicked by another

NATURAL SELECTION

butterfly, Papilio paradoxa. I have since named this
interesting species Diadema anomala (see the Transactions of
the Entomological Society, 1869, p. 285). In this case, and
in that of Diadema misippus, there is no difference in the
habits of the two sexes, which fly in similar localities ; so that
the influence of " external conditions " cannot be invoked
here as it has been in the case of the South American Pieris
pyrrha and allies, where the white males frequent open
sunny places, while the Heliconia-like females haunt the
shades of the forest.

We may impute to the same general cause (the greater
need of protection for the female, owing to her weaker flight,
greater exposure to attack, and supreme importance) — the
fact of the colours of female insects being so very generally
duller and less conspicuous than those of the other sex. And
that it is chiefly due to this cause rather than to what Mr.
Darwin terms " sexual selection " appears to be shown by the
otherwise inexplicable fact, that in the groups which have a
protection of any kind independent of concealment, sexual
differences of colour are either quite wanting or slightly
developed. The Heliconidae and Danaidae, protected by a
disagreeable flavour, have the females as bright and con-
spicuous as the males, and very rarely differing at all from
them. The stinging Hymenoptera have the two sexes equally
well coloured. The Carabidse, the Coccinellidae, Chrysomelidse,
and the Telephori have both sexes equally conspicuous, and
seldom differing in colours. The brilliant Curculios, which
are protected by their hardness, are brilliant in both sexes.
Lastly, the glittering Cetoniadae and Buprestidae, which seem
to be protected by their hard and polished coats, their rapid
motions and peculiar habits, present few sexual differences
of colour, while sexual selection has often manifested itself
by structural differences, such as horns, spines, or other
processes.

Cause of the dull Colours of Female Birds

The same law manifests itself in Birds. The female while
sitting on her eggs requires protection by concealment to a
much greater extent than the male ; and we accordingly find
that in a large majority of the cases in which the male birds

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 81

are distinguished by unusual brilliancy of plumage, the
females are much more obscure, and often remarkably plain-
coloured. The exceptions are such as eminently to prove the
rule, for in most cases we can see a very good reason for
them. In particular, there are a few instances among wading
and gallinaceous birds in which the female has decidedly
more brilliant colours than the male ; but it is a most curious
and interesting fact that in most if not all these cases the
males sit upon the eggs ; so that this exception to the usual
rule almost demonstrates that it is because the process of
incubation is at once very important and very dangerous,
that the protection of obscure colouring is developed. The
most striking example is that of the gray phalarope (Phala-
ropus fulicarius). When in winter plumage, the sexes of this
bird are alike in coloration, but in summer the female is
much the most conspicuous, having a black head, dark wings,
and reddish-brown back, while the male is nearly uniform
brown, with dusky spots. Mr. Gould in his Birds of Great
Britain figures the two sexes in both winter and summer
plumage, and remarks on the strange peculiarity of the usual
colours of the two sexes being reversed, and also on the still
more curious fact that the "male alone sits on the eggs,"
which are deposited on the bare ground. In another British
bird, the dotterell, the female is also larger and more brightly
coloured than the male ; and it seems to be proved that the
males assist in incubation even if they do not perform it
entirely, for Mr. Gould tells us "that they have been shot
with the breast bare of feathers, caused by sitting on the
eggs." The small quail-like birds forming the genus Turnix
have also generally large and bright-coloured females, and we
are told by Mr. Jerdon in his Birds of India that " the natives
report that during the breeding season the females desert
their eggs and associate in flocks while the males are employed
in hatching the eggs." It is also an ascertained fact that the
females are more bold and pugnacious than the males. A
further confirmation of this view is to be found in the fact
(not hitherto noticed) that in a large majority of the cases in
which bright colours exist in both sexes incubation takes
place in a dark hole or in a dome -shaped nest. Female
kingfishers are often equally brilliant with the male, and they
G

82 NATURAL SELECTION HI

build in holes in banks. Bee-eaters, trogons, motmots, and
toucans all build in holes, and in none is there any difference
in the sexes, although they are, without exception, showy
birds. Parrots build in holes in trees, and in the majority of
cases they present no marked sexual difference tending to
concealment of the female. Woodpeckers are in the same
category, since, though the sexes often differ in colour, the
female is not generally less conspicuous than the male.
Wagtails and titmice build concealed nests, and the females
are nearly as gay as their mates. The female of the pretty
Australian bird, Pardalotus punctatus, is very conspicuously
spotted on the upper surface, and it builds in a hole in the
ground. The gay -coloured hang-nests (Icterinae) and the
equally brilliant tanagers may be well contrasted; for the
former, concealed in their covered nests, present little or no
sexual difference of colour — while the open -nested tanagers
have the females dull-coloured and sometimes with almost
protective tints. No doubt there are many individual
exceptions to the rule here indicated, because many and
various causes have combined to determine both the colora-
tion and the habits of birds. These have no doubt acted and
reacted on each other ; and when conditions have changed
one of these characters may often have become modified,
while the other, though useless, may continue by hereditary
descent an apparent exception to what otherwise seems a
very general rule. The facts presented by the sexual differ-
ences of colour in birds and their mode of nesting are on
the whole in perfect harmony with that law of protective
adaptation of colour and form, which appears to have checked
to some extent the powerful action of sexual selection, and to
have materially influenced the colouring of female birds, as it
has undoubtedly done that of female insects.

Use of the gaudy Colours of many Caterpillars
Since this essay was first published a very curious difficulty
has been cleared up by the application of the general principle
of protective colouring. Great numbers of caterpillars are so
brilliantly marked and coloured as to be very conspicuous even
at a considerable distance, and it has been noticed that such
caterpillars seldom hide themselves. Other species, however,

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 83

are green or brown, closely resembling the colours of the
substances on which they feed, while others again imitate
sticks, and stretch themselves out motionless from a twig so
as to look like one of its branches. Now, as caterpillars form
so large a part of the food of birds, it was not easy to under-
stand why any of them should have such bright colours and
markings as to make them specially visible. Mr. Darwin
had put the case to me as a difficulty from another point of
view, for he had arrived at the conclusion that brilliant
coloration in the animal kingdom is mainly due to sexual
selection, and this could not have acted in the case of sexless
larvae. Applying here the analogy of other insects, I reasoned
that since some caterpillars were evidently protected by their
imitative colouring, and others by their spiny or hairy bodies,
the bright colours of the rest must also be in some way useful
to them. I further thought that as some butterflies and
moths were greedily eaten by birds, while others were dis-
tasteful to them, and these latter were mostly of conspicuous
colours, so probably these brilliantly coloured caterpillars were
distasteful, and therefore never eaten by birds. Distasteful-
ness alone would, however, be of little service to caterpillars,
because their soft and juicy bodies are so delicate that if
seized and afterwards rejected by a bird, they would almost
certainly be killed. Some constant and easily perceived
signal was therefore necessary to serve as a warning to birds
never to touch these uneatable kinds, and a very gaudy
and conspicuous colouring with the habit of fully exposing
themselves to view becomes such a signal, being in strong
contrast with the green or brown tints and retiring habits
of the eatable kinds. The subject was brought by me
before the Entomological Society (see Proceedings, 4th March
1867), in order that those members having opportunities
for making observations might do so in the following
summer ; and I also wrote a letter to the Field news-
paper, begging that some of its readers would co-operate
in making observations on what insects were rejected by
birds, at the same time fully explaining the great interest
and scientific importance of the problem. It is a curious
example of how few of the country readers of that paper are
at all interested in questions of simple natural history, that I

84 NATURAL SELECTION in

only obtained one answer from a gentleman in Cumberland,
who gave me some interesting observations on the general
dislike and abhorrence of all birds to the "Gooseberry
Caterpillar," probably that of the Magpie moth (Abraxas
grossulariata). Neither young pheasants, partridges, nor wild
ducks could be induced to eat it, sparrows and finches never
touched it, and all birds to whom he offered it rejected it
with evident dread and abhorrence. It will be seen that these
observations are confirmed by those of two members of the
Entomological Society, to whom we are indebted for more
detailed information.

In March 1869 Mr. J. Jenner Weir communicated a
valuable series of observations made during many years, but
more especially in the two preceding summers, in his aviary,
containing the following birds of more or less insectivorous
habits : — Kobin, Yellow - hammer, Eeed - bunting, Bullfinch,
Chaffinch, Crossbill, Thrush, Tree-pipit, Siskin, and Redpoll.
He found that hairy caterpillars were uniformly rejected ;
five distinct species were quite unnoticed by all his birds, and
were allowed to crawl about the aviary for days with impunity.
The spiny caterpillars of the Tortoiseshell and Peacock but-
terflies were equally rejected ; but in both these cases Mr.
Weir thinks it is the taste, not the hairs or spines, that
is disagreeable, because some very young caterpillars of a
hairy species were rejected although no hairs were developed,
and the smooth pupae of the above:- named butterflies were
refused as persistently as the spined larvse. In these cases,
then, both hairs and spines would seem to be mere signs of
uneatableness.

His next experiments were with those smooth gaily-
coloured caterpillars which never conceal themselves, but on
the contrary appear to court observation. Such are those of
the Magpie moth (Abraxas grossulariata), whose caterpillar is
conspicuously white and black spotted — the Diloba cseruleo-
cephala, whose larva is pale yellow with a broad blue or
green lateral band — the Cucullia verbasci, whose larva is
greenish white with yellow bands and black spots, and
Anthrocera filipendulae (the six spot Burnet moth), whose
caterpillar is yellow with black spots. These were given to
the birds at various times, sometimes mixed with other kinds

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 85

of larvae which were greedily eaten, but they were in every
case rejected apparently unnoticed, and were left to crawl
about till they died.

The next set of observations were on the dull-coloured
and protected larvae, and the results of numerous experiments
are thus summarised by Mr. Weir. "All caterpillars whose
habits are nocturnal, which are dull -coloured, with fleshy
bodies and smooth skins, are eaten with the greatest avidity.
Every species of green caterpillar is also much relished. All
Geometrae, whose larvae resemble twigs as they stand out
from the plant on their anal prolegs, are invariably eaten."

At the same meeting Mr. A. G-. Butler, of the British
Museum, communicated the results of his observations with
lizards, frogs, and spiders, which strikingly corroborate those
of Mr. Weir. Three green lizards (Lacerta viridis), which he
kept for several years, were very voracious, eating all kinds
of food, from a lemon cheesecake to a spider, and devouring
flies, caterpillars, and humble bees; yet there were some
caterpillars and moths which they would seize only to drop
immediately. Among these the principal were the caterpillar
of the Magpie moth (Abraxas grossulariata) and the perfect
six spot Burnet moth (Anthrocera filipendulae). These would
be first seized but invariably dropped in disgust, and after-
wards left unmolested. Subsequently frogs were kept and
fed with caterpillars from the garden, but two of these — that
of the before-mentioned Magpie moth, and that of the V.
moth (Halia wavaria), which is green with conspicuous white
or yellow stripes and black spots — were constantly rejected.
When these species were first offered, the frogs sprang at
them eagerly and licked them into their mouths ; no sooner,
however, had they done so than they seemed to be aware of
the mistake that they had made, and sat with gaping mouths,
rolling their tongues about until they had got quit of the
nauseous morsels.

With spiders the same thing occurred. These two cater-
pillars were repeatedly put into the webs both of the
geometrical and hunting spiders (Epeira diadema and Lycosa
sp.), but in the former case they were cut out and allowed to
drop ; in the latter, after disappearing in the jaws of their
captor down his dark silken funnel, they invariably reappeared,

NATURAL SELECTION

either from below or else taking long strides up the funnel
again. Mr. Butler has observed lizards fight with and finally
devour humble bees, and a frog sitting on a bed of stone-crop
leap up and catch the bees which flew over his head, and
swallow them, in utter disregard of their stings. It is
evident, therefore, that the possession of a disagreeable taste
or odour is a more effectual protection to certain conspicuous
caterpillars and moths than would be even the possession of
a sting.

The observations of these two gentlemen supply a very
remarkable confirmation of the hypothetical solution of the diffi-
culty which I had given two years before. And as it is generally
acknowledged that the best test of the truth and complete-
ness of a theory is the power which it gives us of prevision,
we may, I think, fairly claim this as a case in which the
power of prevision has been successfully exerted, and therefore
as furnishing a very powerful argument in favour of the
truth of the theory of Natural Selection.

I have now completed a brief, and necessarily very im-
perfect, survey of the various ways in which the external form
and colouring of animals is adapted to be useful to them,
either by concealing them from their enemies or from the
creatures they prey upon. It has, I hope, been shown that
the subject is one of much interest, both as regards a true com-
prehension of the place each animal fills in the economy of
nature, and the means by which it is enabled to maintain that
place ; and also as teaching us how important a part is played
by the minutest details in the structure of animals, and how
complicated and delicate is the equilibrium of the organic
world.

My exposition of the subject having been necessarily
somewhat lengthy and full of details, it will be as well to
recapitulate its main points.

There is a general harmony in nature between the colours
of an animal and those of its habitation. Arctic animals are
white, desert animals are sand -coloured ; dwellers among
leaves and grass are green ; nocturnal animals are dusky.
These colours are not universal, but are very general, and are

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 87

seldom reversed. Going on a little further, we find birds,
reptiles, and insects so tinted and mottled as exactly to
match the rock, or bark, or leaf, or flower, they are accustomed
to rest upon, — and thereby effectually concealed. Another
step in advance, and we have insects which are formed as
well as coloured so as exactly to resemble particular leaves,
or sticks, or mossy twigs, or flowers ; and in these cases very
peculiar habits and instincts come into play to aid in the
deception and render the concealment more complete. We
now enter upon a new phase of the phenomena, and come to
creatures whose colours neither conceal them nor make them
like vegetable or mineral substances; on the contrary, they
are conspicuous enough, but they completely resemble some
other creature of a quite different group, while they differ
much in outward appearance from those with which all
essential parts of their organisation show them to be really
closely allied. They appear like actors or masqueraders
dressed up and painted for amusement, or like swindlers
endeavouring to pass themselves off for well-known and
respectable members of society. What is the meaning of
this strange travesty ? Does Nature descend to imposture or
masquerade ? We answer, she does not. Her principles are
too severe. There is a use in every detail of her handiwork.
The resemblance of one animal to another is of exactly the
same essential nature as the resemblance to a leaf, or to bark,
or to desert sand, and answers exactly the same purpose. In
the one case the enemy will not attack the leaf or the bark,
and so the disguise is a safeguard ; in the other case it is
found that for various reasons the creature resembled is
passed over, and not attacked by the usual enemies of its
order, and thus the creature that resembles it has an equally
effectual safeguard. We are plainly shown that the disguise
is of the same nature in the two cases, by the occurrence in the
same group of one species resembling a vegetable substance,
while another resembles a living animal of another group;
and we know that the creatures resembled possess an im-
munity from attack, by their being always very abundant,
by their being conspicuous and not concealing themselves,
and by their having generally no visible means of escape from
their enemies ; while, at the same time, the particular quality

NATURAL SELECTION

that makes them disliked is often very clear, such as a nasty
taste or an indigestible hardness. Further examination
reveals the fact that, in several cases of both kinds of dis-
guise, it is the female only that is thus disguised ; and as it
can be shown that the female needs protection much more
than the male, and that her preservation for a much longer
period is absolutely necessary for the continuance of the race,
we have an additional indication that the resemblance is in
all cases subservient to a great purpose — the preservation of
the species.

In endeavouring to explain these phenomena as having
been brought about by variation and natural selection, we
start with the fact that white varieties frequently occur,
and when protected from enemies show no incapacity for
continued existence and increase. We know, further, that
varieties of many other tints occasionally occur ; and as " the
survival of the fittest" must inevitably weed out those
whose colours are prejudicial and preserve those whose
colours are a safeguard, we require no other mode of account-
ing for the protective tints of arctic and desert animals.
But this being granted, there is such a perfectly continuous
and graduated series of examples of every kind of protective
imitation, up to the most wonderful cases of what is termed
" mimicry," that we can find no place at which to draw the
line, and say : So far variation and natural selection will
account for the phenomena, but for all the rest we require a
more potent cause. The counter theories that have been
proposed, that of the " special creation " of each imitative
form, that of the action of " similar conditions of existence "
for some of the cases, and of the laws of " hereditary descent
and the reversion to ancestral forms " for others, — have all
been shown to be beset with difficulties, and the two latter
to be directly contradicted by some of the most constant and
most remarkable of the facts to be accounted for.

General deductions as to Colour in Nature

The important part that "protective resemblance" has

played in determining the colours and markings of many

groups of animals, will enable us to understand the meaning

of one of the most striking facts in nature, the uniformity in

in PROTECTIVE RESEMBLANCES AMONG ANIMALS 89

the colours of the vegetable as compared with the wonderful
diversity of the animal world. There appears no good reason
why trees and shrubs should not have been adorned with as
many varied hues and as strikingly designed patterns as birds
and butterflies, since the gay colours of flowers show that
there is no incapacity in vegetable tissues to exhibit them.
But even flowers themselves present us with none of those
wonderful designs, those complicated arrangements of stripes
and dots and patches of colour, that harmonious blending of
hues in lines and bands and shaded spots, which are so
general a feature in insects. It is the opinion of Mr. Darwin
that we owe much of the beauty of flowers to the necessity
of attracting insects to aid in their fertilisation, and that
much of the development of colour in the animal world is
due to " sexual selection," colour being universally attractive,
and thus leading to its propagation and increase ; but while
fully admitting this, it will be evident, from the facts and
arguments here brought forward, that very much of the
variety both of colour and markings among animals is due to
the supreme importance of concealment, and thus the various
tints of minerals and vegetables have been directly repro-
duced in the animal kingdom, and again and again modified
as more special protection became necessary. We shall thus
have two causes for the development of colour in the animal
world, and shall be better enabled to understand how, by
their combined and separate action, the immense variety we
now behold has been produced. Both causes, however, will
come under the general law of "Utility," the advocacy of
which, in its broadest sense, we owe almost entirely to Mr.
Darwin. A more accurate knowledge of the varied pheno-
mena connected with this subject may not improbably give
us some information both as to the senses and the mental
faculties of the lower animals. For it is evident that if
colours which please us also attract them, and if the various
disguises which have been here enumerated are equally
deceptive to them as to ourselves, then both their powers of
vision and their faculties of perception and emotion must be
essentially of the same nature as our own — a fact of high
philosophical importance in the study of our own nature and
our true relations to the lower animals.

90 NATURAL SELECTION

Conclusion

Although such a store of interesting facts has been already
accumulated, the subject we have been discussing is one of
which comparatively little is really known. The natural
history of the tropics has never yet been studied on the spot
with a full appreciation of " what to observe " in this matter.
The varied ways in which the colouring and form of animals
serve for their protection, their strange disguises as vegetable
or mineral substances, their wonderful mimicry of other
beings, offer an almost unworked and inexhaustible field of
discovery for the zoologist, and will assuredly throw much
light on the laws and conditions which have resulted in the
wonderful variety of colour, shade, and marking which con-
stitutes one of the most pleasing characteristics of the animal
world, but the immediate causes of which it has hitherto
been most difficult to explain.

If I have succeeded in showing that in this wide and
picturesque domain of nature, results which have hitherto
been supposed to depend either upon those incalculable com-
binations of laws which we term chance or upon the direct
volition of the Creator, are really due to the action of
comparatively well-known and simple causes, I shall have
attained my present purpose, which has been to extend the
interest so generally felt in the more striking facts of natural
history to a large class of curious but much neglected details ;
and to further, in however slight a degree, our knowledge of
the subjection of the phenomena of life to the Reign of Law.

IV

ON INSTINCT IN MAN AND ANIMALS

THE most perfect and most striking examples of what is
termed instinct — those in which reason or observation appear
to have the least influence, and which seem to imply the
possession of faculties farthest removed from our own — are to
be found among insects. The marvellous constructive powers
of bees and wasps, the social economy of ants, the careful
provision for the safety of a progeny they are never to see
manifested by many beetles and flies, and the curious pre-
parations for the pupa state by the larvae of butterflies and
moths, are typical examples of this faculty, and are supposed
to be conclusive as to the existence of some power or intelli-
gence very different from that which we derive from our
senses or from our reason.

How Instinct may be best Studied

Whatever we may define instinct to be, it is evidently some
form of mental manifestation, and as we can only judge of mind
by the analogy of our own mental functions and by observa-
tion of the results of mental action in other men and in
animals, it is incumbent on us, first, to study and endeavour
to comprehend the minds of infants, of savage men, and of
animals not very far removed from ourselves, before we
pronounce positively as to the nature of the mental operations
in creatures so radically different from us as insects. We have
not yet even been able to ascertain what are the senses they
possess, or what relation their powers of seeing, hearing, and
feeling have to ours. Their sight may far exceed ours both
in delicacy and in range, and may possibly give them know

NATURAL SELECTION

ledge of the internal constitution of bodies analogous to that
which we obtain by the spectroscope ; and that their visual
organs do possess some powers which ours do not, is indicated
by the extraordinary crystalline rods radiating from the optic
ganglion to the facets of the compound eye, which rods vary
in form and thickness in different parts of their length, and
possess distinctive characters in each group of insects. This
complex apparatus, so different from anything in the eyes of
vertebrates, may subserve some function quite inconceivable
by us, as well as that which we know as vision. There is
reason to believe that insects appreciate sounds of extreme
delicacy, and it is supposed that certain minute organs, plenti-
fully supplied with nerves, and situated in the subcostal vein
of the wing in most insects, are the organs of hearing. But
besides these, the Orthoptera (such as grasshoppers, etc.) have
what are supposed to be ears on their fore legs, and Mr.
Lowne believes that the little stalked balls, which are the
sole remnants of the hind wings in flies, are also organs of
hearing or of some analogous sense. In flies, too, the third
joint of the antennae contains thousands of nerve-fibres, which
terminate in small open cells, and this Mr. Lowne believes to
be the organ of smell, or of some other, perhaps new, sense.
It is quite evident, therefore, that insects may possess senses
which give them a knowledge of that which we can never
perceive, and enable them to perform acts which to us are
incomprehensible. In the midst of this complete ignorance
of their faculties and inner nature, is it wise for us to judge
so boldly of their powers by a comparison with our own ?
How can we pretend to fathom the profound mystery of their
mental nature, and decide what, and how much, they can
perceive or remember, reason or reflect ! To leap at one
bound from our own consciousness to that of an insect's is as
unreasonable and absurd as if, with a pretty good knowledge
of the multiplication table, we were to go straight to the
study of the calculus of functions, or as if our comparative
anatomists should pass from the study of man's bony structure
to that of the fish, and, without any knowledge of the
numerous intermediate forms, were to attempt to determine
the homologies between these distant types of vertebrata.
In such a case would not error be inevitable, and would not

ON INSTINCT IN MAN AND ANIMALS

continued study in the same direction only render the
erroneous conclusions more ingrained and more irremovable.

Definition of Instinct

Before going further into this subject we must determine
what we mean by the term instinct. It has been variously
defined as — " disposition operating without the aid of instruc-
tion or experience," " a mental power totally independent of
organisation," or "a power enabling an animal to do that
which, in those things man can do, results from a chain of
reasoning, and in things which man cannot do, is not to be
explained by any efforts of the intellectual faculties." We
find, too, that the word instinct is very frequently applied to
acts which are evidently the result either of organisation or
of habit. The colt or calf is said to walk instinctively, almost
as soon as it is born ; but this is solely due to its organisation,
which renders walking both possible and pleasurable to it.
So we are said instinctively to hold out our hands to save
ourselves from falling, but this is an acquired habit, which
the infant does not possess. It appears to me that instinct
should be defined as — "the performance by an animal of
complex acts, absolutely without instruction or previously
acquired knowledge." Thus, acts are said to be performed
by birds in building their nests, by bees in constructing their
cells, and by many insects in providing for the future wants
of themselves or their progeny, without ever having seen such
acts performed by others, and without any knowledge of why
they perform them themselves. This is expressed by the
very common term "blind instinct." But we have here a
number of assertions of matters of fact, which, strange to say,
have never been proved to be facts at all. They are thought
to be so self-evident that they may be taken for granted.
No one has ever yet obtained the eggs of some bird which
builds an elaborate nest, hatched these eggs by steam or
under a quite distinct parent, placed them afterwards in an
extensive aviary or covered garden, where the situation and
the materials of a nest similar to that of the parent birds may
be found, and then seen what kind of nest these birds would
build. If under these rigorous conditions they choose the
same materials, the same situation, and construct the nest in

94 NATURAL SELECTION iv

the same way and as perfectly as their parents did, instinct
would be proved in their case ; now it is only assumed, and
assumed, as I shall show further on, without any sufficient
reason. So, no one has ever carefully taken the pupae of a
hive of bees out of the comb, removed them from the presence
of other bees, and loosed them in a large conservatory with
plenty of flowers and food, and observed what kind of cells
they would construct. But till this is done, no one can say
that bees build without instruction, no one can say that with
every new swarm there are no bees older than those of the
last brood, who may be the teachers in forming the new
comb. Now, in a scientific inquiry, a point which can be
proved should not be assumed, and a totally unknown power
should not be brought in to explain facts, when known
powers may be sufficient. For both these reasons I decline to
accept the theory of instinct in any case where all other
possible modes of explanation have not been exhausted.

Does Man possess Instincts

Many of the upholders of the instinctive theory maintain
that man has instincts exactly of the same nature as those of
animals, but more or less liable to be obscured by his reason-
ing powers ; and as this is a case more open to our observation
than any other, I will devote a few pages to its consideration.
Infants are said to suck by instinct, and afterwards to walk
by the same power, while in adult man the most prominent
case of instinct is supposed to be the powers possessed by
savage races to find their way across a trackless and previously
unknown wilderness. Let us take first the case of the infant's
sucking. It is sometimes absurdly stated that the new-born
infant " seeks the breast," and this is held to be a wonderful
proof of instinct. No doubt it would be if true, but Unfortu-
nately for the theory it is totally false, as every nurse and
medical man can testify. Still, the child undoubtedly sucks
without teaching, but this is one of those simple acts depend-
ent upon organisation, which cannot properly be termed
instinct, any more than breathing or muscular motion. Any
object of suitable size in the mouth of an infant excites the
nerves and muscles so as to produce the act of suction, and
when, at a little later period, the will comes into play, the

iv ON INSTINCT IN MAN AND ANIMALS 95

pleasurable sensations consequent on the act lead to its con-
tinuance. So walking is evidently dependent on the arrange-
ment of the bones and joints, and the pleasurable exertion of
the muscles, which lead to the vertical posture becoming
gradually the most agreeable one ; and there can be little
doubt that an infant would learn of itself to walk, even if
suckled by a wild beast.

Haw Indians travel through unknown and trackless Forests
Let us now consider the fact of Indians finding their way
through forests they have never traversed before. This is
much misunderstood, for I believe it is only performed under
such special conditions as at once to show that instinct has
nothing to do with it. A savage, it is true, can find his way
through his native forests in a direction in which he has never
traversed them before ; but this is because from infancy he
has been used to wander in them, and to find his way by
indications which he has observed himself or learnt from
others. Savages make long journeys in many directions, and,
their whole faculties being directed to the subject, they gain
a wide and accurate knowledge of the topography, not only of
their own district, but of all the regions round about. Every
one who has travelled in a new direction communicates his
knowledge to those who have travelled less, and descriptions
of routes and localities, and minute incidents of travel, form
one of the main staples of conversation round the evening fire.
Every wanderer or captive from another tribe adds to the
store of information, and as the very existence of individuals
and of whole families and tribes depends upon the complete-
ness of this knowledge, all the acute perceptive faculties of
the adult savage are devoted to acquiring and perfecting it.
The good hunter or warrior thus comes to know the bearing
of every hill and mountain range, the directions and junctions
of all the streams, the situation of each tract characterised by
peculiar vegetation, not only within the area he has himself
traversed, but for perhaps a hundred miles around it. His
acute observation enables him to detect the slightest undula-
tions of the surface, the various changes of subsoil and altera-
tions in the character of the vegetation, that would be
imperceptible or meaningless to a stranger. His eye is always

NATURAL SELECTION

open to the direction in which he is going ; the mossy side
of trees, the presence of certain plants under the shade of
rocks, the morning and evening flight of birds, are to him
indications of direction almost as sure as the sun in the
heavens. Now, if such a savage is required to find his way
across this country in a direction in which he has never been
before, he is quite equal to the task. By however circuitous
a route he has come to the point he is to start from, he has
observed all the bearings and distances so well, that he knows
pretty nearly where he is, the direction of his own home and
that of the place he is required to go to. He starts towards
it, and knows that by a certain time he must cross an upland
or a river, that the streams should flow in a certain direction,
and that he should cross some of them at a certain distance
from their sources. The nature of the soil throughout the
whole region is known to him, as well as all the great features
of the vegetation. As he approaches any tract of country he
has been in or near before, many minute indications guide
him, but he observes them so cautiously that his white
companions cannot perceive by what he has directed his course.
Every now and then he slightly changes his direction, but he
is never confused, never loses himself, for he always feels at
home ; till at last he arrives at a well-known country, and
directs his course so as to reach the exact spot desired. To
the Europeans whom he guides he seems to have come with-
out trouble, without any special observation, and in a nearly
straight unchanging course. They are astonished, and ask if
he has ever been the same route before, and when he answers
"No," conclude that some unerring instinct could alone
have guided him. But take this same man into another
country very similar to his own, but with other streams and
hills, another kind of soil, with a somewhat different vegeta-
tion and animal life ; and after bringing him by a circuitous
route to a given point, ask him to return to his starting-place,
by a straight line of fifty miles through the forest, and he will
certainly decline to attempt it, or, attempting it, will more or
less completely fail. His supposed instinct does not act out
of his own country.

A savage, even in a new country, has, however, undoubted
advantages from his familiarity with forest life, his entire

iv ON INSTINCT IN MAN AND ANIMALS 97

fearlessness of being lost, his accurate perception of direction
and of distance, and he is thus able very soon to acquire a
knowledge of the district that seems marvellous to a civilised
man ; but my own observation of savages in forest countries
has convinced me that they find their way by the use of no
other faculties than those which we ourselves possess. It
appears to me, therefore, that to call in the aid of a new and
mysterious power to account for savages being able to do that
which, under similar conditions, we could almost all of us
perform, although perhaps less perfectly, is almost ludicrously
unnecessary.

In the next essay I shall attempt to show that much of
what has been attributed to instinct in birds can be also
very well explained by crediting them with those faculties of
observation, memory, and imitation, and with that limited
amount of reason, which they undoubtedly exhibit.

THE PHILOSOPHY OF BIRDS NESTS1

Instinct or Reason in the Construction of Birds' Nests

BIRDS, we are told, build their nests by instinct, while man
constructs his dwelling by the exercise of reason. Birds
never change, but continue to build for ever on the self-same
plan ; man alters and improves his houses continually.
Eeason advances ; instinct is stationary.

This doctrine is so very general that it may almost be
said to be universally adopted. Men who agree on nothing
else accept this as a good explanation of the facts. Philo-
sophers and poets, metaphysicians and divines, naturalists
and the general public, not only agree in believing this to be
probable, but even adopt it as a sort of axiom that is so self-
evident as to need no proof, and use it as the very foundation
of their speculations on instinct and reason. A belief so
general, one would think, must rest on indisputable facts,
and be a logical deduction from them. Yet I have come to
the conclusion that not only is it very doubtful, but absolutely
erroneous ; that it not only deviates widely from the truth,
but is in almost every particular exactly opposed to it. I
believe, in short, that birds do not build their nests by
instinct ; that man does not construct his dwelling by reason ;
that birds do change and improve when affected by the same
causes that make men do so ; and that mankind neither alter
nor improve when they exist under conditions similar to
those which are almost universal among birds.

1 First published in the Intellectual Observer, July 1867 ; reprinted in
Contributions, etc., with considerable alterations and additions ; and with
further additions in the present volume.

THE PHILOSOPHY OF BIRDS' NESTS

Do Men build by Reason or by Imitation ?

Let us first consider the theory of reason, as alone deter-
mining the domestic architecture of the human race. Man,
as a reasonable animal, it is said, continually alters and
improves his dwelling. This I entirely deny. As a rule, he
neither alters nor improves, any more than the birds do. What
have the houses of most savage tribes improved from, each as
invariable as the nest of a species of bird ? The tents of the
Arab are the same now as they were two or three thousand
years ago, and the mud villages of Egypt can scarcely have
improved since the time of the Pharaohs. The palm-leaf huts
and hovels of the various tribes of South America and the
Malay Archipelago, what have they improved from since
those regions were first inhabited? The Patagonian's rude
shelter of leaves, the hollowed bank of the South African
Earthmen, we cannot even conceive to have been ever
inferior to what they now are. Even nearer home, the Irish
turf cabin and the Highland stone shelty can hardly have
advanced much during the last two thousand years. Now,
no one imputes this stationary condition of domestic archi-
tecture among these savage tribes to instinct, but to simple
imitation from one generation to another, and the absence of
any sufficiently powerful stimulus to change or improvement.
No one imagines that if an infant Arab could be transferred
to Patagonia or to the Highlands, it would, when it grew up,
astonish its foster-parents by constructing a tent of skins. On
the other hand, it is quite clear that physical conditions,
combined with the degree of civilisation arrived at, almost
necessitate certain types of structure. The turf, or stones,
or snow — the palm-leaves, bamboo, or branches — which are
the materials of houses in various countries, are used because
nothing else is so readily to be obtained. The Egyptian
peasant has none of these, not even wood. What, then, can
he use but mud ? In tropical foresi^countries, the bamboo
and the broad palm -leaves are the natural material for houses,
and the form and mode of structure will be decided in part
by the nature of the country, whether hot or cool, whether
swampy or. dry, whether rocky or plain, whether frequented
by wild beasts, or whether subject to the attacks of enemies.

100 NATURAL SELECTION v

When once a particular mode of building has been adopted,
and has become confirmed by habit and by hereditary custom,
it will be long retained, even when its utility has been lost
through changed conditions, or through migration into a very
different region. As a general rule, throughout the whole
continent of America, native houses, when permanent, are
built directly upon the ground — strength and security being
given by thickening the low walls and the roof. In almost
the whole of the Malay Islands, on the contrary, the houses
are raised on posts, often to a great height, with an open
bamboo floor ; and the whole structure is exceedingly slight
and thin. Now, what can be the reason of this remarkable
difference between countries, many parts of which are
strikingly similar in physical conditions, natural productions,
and the state of civilisation of their inhabitants ? We appear
to have some clue to it in the supposed origin and migrations
of their respective populations. The indigenes of tropical
America are believed to have immigrated from the north —
from a country where the winters are severe, and raised
houses with open floors would be hardly habitable. They
moved southwards by land along the mountain ranges and
uplands, and in an altered climate continued the mode of
construction of their forefathers, modified only by the new
materials they met with. By minute observations of the
Indians of the Amazon Valley, Mr. Bates arrived at the
conclusion that they were comparatively recent immigrants
from a colder climate. He says : " No one could live long
among the Indians of the Upper Amazon without being
struck with their constitutional dislike to the heat. . . . Their
skin is hot to the touch, and they perspire little. . . . They
are restless and discontented in hot, dry weather, but cheerful
on cool days, when the rain is pouring down their naked
backs." And, after giving many other details, he concludes,
" How different all this is with the Negro, the true child of
tropical climes ! The impression gradually forced itself on
my mind that the Red Indian lives as an immigrant or
stranger in these hot regions, and that his constitution was
not originally adapted, and has not since become perfectly
adapted, to the climate."

The Malay races, on the other hand, are no doubt very

v THE PHILOSOPHY OF BIRDS' NESTS 101

ancient inhabitants of the hottest regions, and are par-
ticularly addicted to forming their first settlements at the
mouths of rivers or creeks, or in land-locked bays and inlets.
They are a pre-eminently maritime or semi-aquatic people,
to whom a canoe is a necessary of life, and who will never
travel by land if they can do so by water. In accordance
with these tastes, they have built their houses on posts in
the water, after the manner of the lake-dwellers of ancient
Europe ; and this mode of construction has become so con-
firmed, that even those tribes which have spread far into the
interior, on dry plains and rocky mountains, continue to build
in exactly the same manner, and find safety in the height to
which they elevate their dwellings above the ground.

Why does each Bird build a peculiar kind of Nest ?

These general characteristics of the abode of savage man
will be found to be exactly paralleled by the nests of birds.
Each species uses the materials it can most readily obtain,
and builds in situations most congenial to its habits. The
wren, for example, frequenting hedgerows and low thickets,
builds its nest generally of moss, a material always found
where it lives, and among which it probably obtains much of
its insect food ; but it varies sometimes, using hay or feathers
when these are at hand. Eooks dig in pastures and ploughed
fields for grubs, and in doing so must continually encounter
roots and fibres. These are used to line its nest. What more
natural ! The crow feeding on carrion, dead rabbits, and
lambs, and frequenting sheep-walks and warrens, chooses fur
and wool to line its nest. The lark frequents cultivated
fields, and makes its nest, on the ground, of dry grass-stems
lined with finer grass and rootlets — materials the most easy
to meet with, and the best adapted to its needs. The king-
fisher makes its nest of the bones of the fish which it has
eaten. Swallows use clay and mud from the margins of the
ponds and rivers over which they find their insect food. The
materials of birds' nests, like those used by savage man for
his house, are, then, those which come first to hand ; and it
certainly requires no more special instinct to select them in
one case than in the other.

But, it will be said, it is not so much the materials as the

102 NATURAL SELECTION v

form and structure of nests, that vary so much, and are so
wonderfully adapted to the wants and habits of each species ;
how are these to be accounted for except by instinct? I
reply : They may be in a great measure explained by the
general habits of the species, the nature of the tools they
have to work with, and the materials they can most easily
obtain, with the very simplest adaptations of means to an
end, quite within the mental capacities of birds. The delicacy
and perfection of the nest will bear a direct relation to the
size of the bird, its structure and habits. That of the wren
or the humming-bird is perhaps not finer or more beautiful in
proportion than that of the blackbird, the magpie, or the
crow. The wren, having a slender beak, long legs, and great
activity, is able with great ease to form a well- woven nest of
the finest materials, and places it in thickets and hedgerows
which it frequents in its search for food. The titmouse,
haunting fruit-trees and walls, and searching in cracks and
crannies for insects, is naturally led to build in holes where it
has shelter and security; while its great activity, and the
perfection of its tools (bill and feet) enable it readily to form
a beautiful receptacle for its eggs and young. Pigeons
having heavy bodies and weak feet and bills (imperfect tools
for forming a delicate structure) build rude, flat nests of
sticks, laid across strong branches, which will bear their
weight and that of their bulky young. They can do no
better. The Caprimulgidae have the most imperfect tools of
all, feet that will not support them except on a flat surface
(for they cannot truly perch) and a bill excessively broad,
short, and weak, and almost hidden by feathers and bristles.
They cannot build a nest of twigs or fibres, hair or moss, like
other birds, and they therefore generally dispense with one
altogether, laying their eggs on the bare ground, or on the
stump or flat limb of a tree. The clumsy hooked bills, short
necks and feet, and heavy bodies of parrots, render them
quite incapable of building a nest like most other birds.
They cannot climb up a branch without using both bill and
feet ; they cannot even turn round on a perch without holding
on with their bill. How, then, could they inlay, or weave,
or twist the materials of a nest ? Consequently they all lay
in holes of trees, the tops of rotten stumps, or in deserted

v THE PHILOSOPHY OF BIRDS' NESTS 103

ants' nests, the soft materials of which they can easily hollow
out.

Many terns and sandpipers lay their eggs on the bare
sand of the sea-shore, and no doubt the Duke of Argyll is
correct when he says that the cause of this habit is not that
they are unable to form a nest, but that, in such situations,
any nest would be conspicuous and lead to the discovery
of the eggs.' The choice of place is, however, evidently
determined by the habits of the birds, who, in their daily
search for food, are continually roaming over extensive tide-
washed flats. Gulls vary considerably in their mode of
nesting, but it is always in accordance with their structure
and habits. The situation is either on a bare rock or on
ledges of sea- cliffs, in marshes or on weedy shores. The
materials are sea- weed, tufts of grass or rushes, or the ddbris
of the shore, heaped together with as little order and con-
structive art as might be expected from the webbed feet and
clumsy bill of these birds, the latter better adapted for seizing
fish than for forming a delicate nest. The long-legged broad-
billed flamingo, who is continually stalking over muddy flats
in search of food, heaps up the mud into a conical stool, on
the top of which it lays its eggs. The bird can thus sit
upon them conveniently, and they are kept dry, out of reach
of the tides.

Now I believe that throughout the whole class of birds
the same general principles will be found to hold good,
sometimes distinctly, sometimes more obscurely apparent,
according as the habits of the species are more marked, or
their structure more peculiar. It is true that, among birds
differing but little in structure or habits, we see considerable
diversity in the mode of nesting, but we are now so well
assured that important changes of climate and of the earth's
surface have occurred within the period of existing species,
that it is by no means difficult to see how such differences
have arisen. Simple habits are known to be hereditary, and
as the area now occupied by each species is different from
that of every other, we may be sure that such changes would
act differently upon each, and would often bring together
species which had acquired their peculiar habits in distinct
regions and under different conditions.

104 NATURAL SELECTION v

How do Young Birds learn to Build their first Nest ?

But it is objected, birds do not learn to make their nest as
man does to build, for all birds will make exactly the same
nest as the rest of their species, even if they have never seen
one, and it is instinct alone that can enable them to do this.
No doubt this would be instinct if it were true, and I simply
ask for proof of the fact. This point, although so important
to the question at issue, is always assumed without proof,
and even against proof, for what facts there are, are opposed
to it. Birds brought up from the egg in cages do not make
the characteristic nest of their species, even though the
proper materials are supplied them, and often make no nest
at all, but rudely heap together a quantity of materials ; and
the experiment has never been fairly tried of turning out a
pair of birds so brought up into an enclosure covered with
netting, and watching the result of their untaught attempts at
nest-making. With regard to the songs of birds, however,
which is thought to be equally instinctive, the experiment
has been tried, and it is found that young birds never have
the song peculiar to their species if they have not heard it,
whereas they acquire very easily the song of almost any
other bird with which they are associated.

Do Birds sing by Instinct or by Imitation ?
The Hon. Daines Barrington was of opinion that " notes
in birds are no more innate than language is in man, and
depend entirely on the master under which they are bred, as
far as their organs will enable them to imitate the sounds which
they have frequent opportunities of hearing." He has given
an account of his experiments in the Philosophical Transactions
for 1773 (vol. Ixiii.) He says : "I have educated nestling linnets
under the three best singing larks — the skylark, woodlark, and
titlark, every one of which, instead of the linnet's song,
adhered entirely to that of their respective instructors.
When the note of the titlark linnet was thoroughly fixed, I
hung the bird in a room with two common linnets for a
quarter of a year, which were full in song; the titlark
linnet, however, did not borrow any passage from the
linnet's song, but adhered steadfastly to that of the titlark."

v THE PHILOSOPHY OF BIRDS' NESTS 105

He then goes on to say that birds taken from the nest at two
or three weeks old have already learnt the call-note of their
species. To prevent this the birds must be taken from the
nest when a day or two old, and he gives an account of a
goldfinch which he saw at Knighton in Radnorshire, and
which sang exactly like a wren, without any portion of the
proper note of its species. This bird had been taken from
the nest at two or three days old, and had been hung at a
window opposite a small garden, where it had undoubtedly
acquired the notes of the wren without having any oppor-
tunity of learning even the call of the goldfinch.

He also saw a linnet, which had been taken from the
nest when only two or three days old, and which, not having
any other sounds to imitate, had learnt almost to articulate,
and could repeat the words, " Pretty Boy," and some other short
sentences.

Another linnet was educated by himself under a vengolina
(a small African finch, which he says sings better than any
foreign bird but the American mocking bird), and it imitated
its African master so exactly that it was impossible to dis-
tinguish the one from the other.

Still more extraordinary was the case of a common house
sparrow, which only chirps in a wild state, but which learnt
the song of the linnet and goldfinch by being brought up
near those birds.

The Rev. W. H. Herbert made similar observations, and
states that the young whinchat and wheatear, which have
naturally little variety of song, are ready in confinement to
learn from other species, and become much better songsters.
The bullfinch, whose natural notes are weak, harsh, and
insignificant, has nevertheless a wonderful musical faculty,
since it can be taught to whistle complete tunes. The night-
ingale, on the other hand, whose natural song is so beautiful,
is exceedingly apt in confinement to learn tkat of other birds
instead. Bechstein gives an account of a redstart which had
built under the eaves of his house, which imitated the song
of a caged chaffinch in a window underneath, while another
in his neighbour's garden repeated some of the notes of a
blackcap, which had a nest close by.

These facts, and many others which might be quoted,

106 NATURAL SELECTION v

render it certain that the peculiar notes of birds are acquired
by imitation, as surely as a child learns English or French,
not by instinct, but by hearing the language spoken by its
parents.

It is especially worthy of remark that, for young birds to
acquire a new song correctly, they must be taken out of
hearing of their parents very soon, for in the first three or
four days they have already acquired some knowledge of the
parent notes, which they will afterwards imitate. This shows
that very young birds can both hear and remember, and it
would be very extraordinary if, after they could see, they
could neither observe nor recollect, and could live for days
and weeks in a nest and know nothing of its materials and
the manner of its construction. During the time they are
learning to fly and return often to the nest, they must be able
to examine it inside and out in every detail, and as we have
seen that their daily search for food invariably leads them
among the materials of which it is constructed, and among
places similar to that in which it is placed, is it so very
wonderful that when they want one themselves they should
make one like it ? How else, in fact, should they make it ?
Would it not be much more remarkable if they went out of
their way to get materials quite different from those used in
the parent nest, if they arranged them in a way they had seen
no example of, and formed the whole structure differently
from that in which they themselves were reared, and which
we may fairly presume is that which their whole organisation
is best adapted to put together with celerity and ease ? It
has, however, been objected that observation, imitation, or
memory can have nothing to do with a bird's architectural
powers, because the young birds, which in England are born
in May or June, will proceed in the following April or May
to build a nest as perfect and as beautiful as that in which it
was hatched, although it could never have seen one built.
But surely the young birds before they left the nest had
ample opportunities of observing its form, its size, its position,
the materials of which it was constructed, and the manner in
which those materials were arranged. Memory would retain
these observations till the following spring, when the materials
would come in their way during their daily search for food,

v THE PHILOSOPHY OF BIRDS' NESTS 107

and it seems highly probable that the older birds would begin
building first, and that those born the preceding summer would
follow their example, learning from them how the foundations
of the nest are laid and the material put together.1

Again, we have no right to assume that young birds gene-
rally pair together. It seems probable that in each pair there
is most frequently only one bird born the preceding summer,
who would be guided, to some extent, by its partner.

My friend, Dr. Eichard Spruce, the well-known traveller
and botanist, thinks this is the case, and has kindly allowed
me to publish the following observations, which he sent me
after reading my book.

How young Birds may learn to build Nests
" Among the Indians of Peru and Ecuador, many of whose
customs are relics of the semi-civilisation that prevailed before
the Spanish conquest, it is usual for the young men to marry
old women, and the young women old men. A young man,
they say, accustomed to be tended by his mother, would fare
ill if he had only an ignorant young girl to take care of him ;
and the girl herself would be better off with a man of mature
years, capable of supplying the place of a father to her.

" Something like this custom prevails among many animals.
A stout old buck can generally fight his way to the doe of his
choice,, and indeed of as many does as he can manage ; but a
young buck ' of his first horns ' must either content himself
with celibacy, or with some dame well-stricken in years.

" Compare the nearly parallel case of the domestic cock
and of many other birds. Then consider the consequences
amongst birds that pair, if an old cock sorts with a young
hen and an old hen with a young cock, as I think is certainly
the case with blackbirds and others that are known to fight
for the youngest and handsomest females. One of each pair

1 It has been very pertinently remarked by a friend that, if young birds
did observe the nest they were reared in, they would consider it to be a
natural production, like the leaves and branches and matted twigs that sur-
rounded it, and could not possibly conclude that their parents had constructed
the one and not the other. This may be a valid objection, and if so, we shall
have to depend on the mode of instruction described in the succeeding para-
graphs, but the question can only be finally decided by a careful set of
experiments.

108 NATURAL SELECTION v

being already an ' old bird,' will be competent to instruct its
younger partner (not only in the futility of ' chaff,' but) in the
selection of a site for a nest and how to build it ; then, how
eggs are hatched and young birds reared.

" Such, in brief, is my idea of how a bird on its first
espousals may be taught the Whole Duty of the married
state."

On this difficult point I have sought for information from
some of our best field ornithologists, but without success, as it
is in most cases impossible to distinguish old from young
birds after the first year. I am informed, however, that the
males of blackbirds, sparrows, and many other kinds fight
furiously, and the conqueror of course has the choice of a
mate. Dr. Spruce's view is at least as probable as the
contrary one (that young birds, as a rule, pair together), and
it is to some extent supported by the celebrated American
observer, Wilson, who strongly insists on the variety in the
nests of birds of the same species, some being so much better
finished than others ; and he believes that the less perfect nests
are built by the younger, the more perfect by the older, birds.

Nearly a century ago the Swiss naturalist, Leroy, made a
similar observation. He maintained that there is a distinctly
perceptible inferiority in the nests built by young birds ; and
he further remarks that the best constructed nests are made
by birds whose young remain a long time in them, and thus
have more opportunity of learning how they are made. He
says that the nests of young birds are ill made and badly
situated, and that these defects are remedied in time, when
their builders have been instructed by a sense of the incon-
veniences they have endured. He maintains that nests of the
same species of bird differ as much as human dwellings, and
that of a hundred swallows' nests no two are exactly alike ;
and he imputes to want of long -continued observation our
failure to discover improvement in them.1

At all events, till the crucial experiment is made, and a
pair of wild birds, raised from the egg without ever seeing a
nest, are shown to be capable of making one exactly of the
parental type, I do not think we are justified in calling in the

1 The Intelligence and Perfectibility of Animals from a Philosophic Point
of View. By Charles Georges Leroy.

v THE PHILOSOPHY OF BIRDS' NESTS 109

aid of an unknown and mysterious faculty to do that which
is so strictly analogous to the house-building of savage man.

The observations and experiments of the late Mr. Spalding
may seem opposed to this view, as they undoubtedly prove
some very remarkable instinctive actions on the part of young
chickens hatched in an incubator. These birds appear to
recognise the call of a hen ; and one chick walked or ran
straight towards her, leaping over or running round small
obstacles ; and this only twenty minutes after its eyes had
been allowed to see the light and the first time it had ever
moved its legs. A young chicken, ten minutes after its eyes
had been unveiled for the first time, seized and swallowed
a fly at the first stroke.1

In subsequent papers Mr. Spalding showed that young
swallows could fly well and avoid obstacles on the first
attempt ; that young pigs a few minutes old could hear and
run to their mother, though out of sight ; and that most young
animals give indications of fear at the voice or presence of
their natural enemies.

But in all these cases we have comparatively simple motions
or acts induced by feelings of liking or disliking ; and we can
see that they may be due to definite nervous and muscular
co-ordinations which are essential to the existence of the
species. That a chicken should feel pleasure at the sound of a
hen's voice and pain or fear at that of a hawk, and should
move towards the one and away from the other, is a fact of
the same nature as the liking of an infant for milk and its
dislike of beer with the motion of the head towards the one
and away from the other when offered to it. But when, at a
much later period, with all its senses and powers of motion
fully developed by use and exercise, and with the results of
the experiences of a year's eventful life, the bird proceeds to
perform the highly complex operation of building a nest, we
have no right to assume without direct proof that it will
be guided throughout by instinct alone ; and we have seen
that not only is there no evidence to support this theory, but
that all the facts we possess are directly opposed to it.

Since this essay was published, however, some amount of

1 " On Instinct." Paper read at British Association, sect. D., 1872 ; Nature,
vol. vi. p. 485.

110 NATURAL SELECTION v

experiment to illustrate the question at issue has become
available. Mr. B. T. Lowne, F.E.C.S., had three of the small
ring-doves (Turtur risoria) which had been hatched in the
breeding box of an ordinary dove's cage. They were kept at
first in a similar cage, with some hay, on which the two
hen birds laid eggs and hatched some young. In the follow-
ing April these birds were put into an aviary in the open air,
in which was a large branch of a tree with numerous twigs
and buds, and there was also a breeding box with hay and
straw. Noticing that the older birds perched on the branch
with small pieces of stick in their bills, Mr. Lowne supplied
them with a quantity of twigs and small sticks, and the
very curious and interesting result was that they built a nest
on the branch and laid their eggs in it. But this was not
effected without much difficulty, and only after they had
received assistance. They first seemed to try to fix the twigs
against the wall of the aviary or its roof, and waved them
about above their heads till they dropped them. Mr. Lowne
then fixed some perches for them lower down, and wove some
small branches together to afford an additional resting-place.
They took possession of this and again carried up twigs and
dropped them, and Mr. Lowne then observed that while the
straight smooth twigs fell to the ground those that were forked
often lodged in the branches. He therefore supplied them with
plenty of forked or branched twigs, and by carrying these up
and dropping them (and I presume standing on them, or other-
wise rendering them compact, though this is not mentioned)
they at length (in three days) formed a nest " exactly like
that of a wood-pigeon." This " they lined neatly with straw,"
and each dove laid two eggs in it.1

This experiment, though very interesting, is by no means
satisfactory or conclusive. In the first place, pigeons are the
very rudest of nest-builders, and will sometimes lay their eggs
on a dense flat bough without any nest at all. Then it is clear
that these birds had no notion how to begin to build ; they
required to be assisted, and, as Mr. Lowne says, " as soon as
a few branches had lodged below them, they finished the nest
which accident had commenced for them." Then they lined it with
straw, which is not their habit in a state of nature, but appears
1 Popular Science Revieic, New Series, vol. iii. p. 274.

v THE PHILOSOPHY OF BIRDS' NESTS 111

to have been the result of their having been used to such a
nest. The one thing that remains, and which Mr. Lowne
thinks proves instinct, is their not forming their nest in the
box they had been accustomed to, and their using sticks and
twigs instead of straw only. But they evidently preferred
the light and air and movement of the branch. That was all
in harmony with their special organisation, and was a return to
the habits which were at once the result and the cause of that
organisation. They preferred to make the nest in this pleasant
place, but they did not know how to begin. As soon as the
sticks, lodged by accident, furnished a sufficient base, they car-
ried up more sticks and soon obtained a rude nest. They saw
that smooth straight twigs dropped to the ground, whereas
branched twigs kept in the branches, and they had quite
sense and observation enough to choose the branched twigs
for the purpose. In all this there seems to me to be no proof
of the operation of instinct as usually understood, and the
experiment yet requires trying with some of our native birds
that build elaborate and very distinctive nests, such as the
song-thrush, the gold-crest, the wren or the long-tailed tit. If
several of these could be brought up in strange nests, and
then be turned out into a large wired enclosure containing
shrubs and bushes, and if under these circumstances each built
an unmistakable nest of its own species, the nest-building
instinct would have to be admitted.

The nearest approach to such a test experiment has been
recently furnished by Mr. Charles Dixon. He states that
some young chaffinches (Fringilla Ccelebs) were, taken to New
Zealand and there turned out. They throve well, and a nest
built by a pair of them was photographed, and from this photo-
graph the nest is thus described by Mr. Dixon : " It is evidently
built in the fork of a branch, and shows very little of that neat-
ness of fabrication for which this bird is noted in England. The
cup of the nest is small, loosely put together, apparently lined
with feathers, and the walls of the structure are prolonged
about eighteen inches and hang loosely down the side of the
supporting branch. The whole structure bears some resem-
blance to the nests of the hangnests, with the exception that
the cavity containing the eggs is situated on the top. Clearly
these New Zealand chaffinches were at a loss for a design

112 NATURAL SELECTION v

when fabricating their nest. They had no standard to work
by, no nests of their own kind to copy, no older birds to give
them any instruction, and the result is the abnormal structure
I have just described. Perhaps these chaffinches imitated in
some degree the nest of some New Zealand species ; or it
may be that the few resemblances to the typical nest of the
Palsearctic chaffinch are the results of memory — the dim
remembrance of the nest in which they had been reared, but
which had almost been effaced by novel surroundings and
changed conditions of life. Any way we have here, at least,
a most interesting and convincing proof that birds do not
make their nests by blind instinct, but by imitating the nest
in which they were reared, aided largely by rudimentary
reason and by memory." l

This experiment also leaves much to be desired, but it
undoubtedly shows that instinct alone does not determine
the form and structure of a bird's nest, or we should not see
so great a departure from the type in the case of the New
Zealand chaffinches.

The Skill exhibited in Nest-building Exaggerated

We are too apt to assume that because a nest appears to
us delicately and artfully built, it therefore requires much
special knowledge and acquired skill (or their substitute,
instinct) in the bird who builds it. We forget that it is
formed twig by twig and fibre by fibre, rudely enough at first,
but crevices and irregularities, which must seem huge gaps
and chasms in tiie eyes of the little builders, are filled up by
twigs and stalks pushed in by slender beak and active foot,
and that the wool, feathers, or horsehair are laid thread by
thread, so that the result seems a marvel of ingenuity to us,
just as would the rudest Indian hut to a native of Brobdignag.

Levaillant has given an account of the process of nest-
building by a little African warbler, which sufficiently shows
that a very beautiful structure may be produced with very
little art. The foundation was laid of moss and flax inter-
woven with grass and tufts of cotton, and presented a rude
mass, five or six inches in diameter, and four inches thick.
This was pressed and trampled down repeatedly, so as at last
1 Nature, voL xxxi. p. 533 (April 1885).

v THE PHILOSOPHY OF BIRDS' NESTS 113

to make it into a kind of felt. The birds pressed it with
their bodies, turning round upon them in every direction, so
as to get it quite firm and smooth before raising the sides.
These were added bit by bit, trimmed and beaten with the
wings and feet, so as to felt the whole together, projecting
fibres being now and then worked in with the bill. By these
simple and apparently inefficient means, the inner surface of
the nest was rendered almost as smooth and compact as a
piece of cloth.

Man's Works mainly Imitative

But look at civilised man ! it is said ; look at Grecian, and
Egyptian, and Koman, and Gothic, and modern architecture !
What advance ! what improvement ! what refinements ! This
is what reason leads to, whereas birds remain for ever
stationary. If, however, such advances as these are required
to prove the effects of reason as contrasted with instinct, then
all savage and many half-civilised tribes have no reason, but
build instinctively quite as much as birds do.

Man ranges over the whole earth, and exists under the
most varied conditions, leading necessarily to equally varied
habits. He migrates — he makes wars and conquests — one
race mingles with another — different customs are brought
into contact — the habits of a migrating or conquering race,
are modified by the different circumstances of a new country.
The civilised race which conquered Egypt must have de-
veloped its mode of building in a forest country where timber
was abundant, for it is not probable that the idea of cylin-
drical columns originated in a country destitute of trees. The
pyramids might have been built by an indigenous race, but
not the temples of Luxor and Karnak. In Grecian archi-
tecture almost every characteristic feature can be traced to an
origin in wooden buildings. The columns, the architrave, the
frieze, the fillets, the cantilevers, the form of the roof, all
point to an origin in some southern forest-clad country, and
strikingly corroborate the view derived from philology, that
Greece was colonised from north-western India. But to erect
columns and span them with huge blocks of stone, or marble,
is not an act of reason, but one of pure unreasoning imita-
tion. The arch is the only true and reasonable mode of
covering over wide spaces with stone, and, therefore, Grecian
I

114 NATURAL SELECTION V

architecture, however exquisitely beautiful, is false in prin-
ciple, and is by no means a good example of the application
of reason to the art of building. And what do most of us
do at the present day but imitate the buildings of those that
have gone before us ? We have not even been able to dis-
cover or develop any definite style of building best suited for
us. We have no characteristic national style of architecture,
and to that extent are even below the birds, who have each
their characteristic form of nest, exactly adapted to their
wants and habits.

Birds do Alter and Improve their Nests when altered Con-
ditions require it

The great uniformity in the architecture of each species of
bird which has been supposed to prove a nest-building instinct,
may, therefore, fairly be imputed to the uniformity of the
conditions under which each species lives. Their range is
often limited, and they very seldom permanently change
their country, so as to be placed in new conditions. When,
however, new conditions do occur, they take advantage of
them just as freely and wisely as man could do. The
chimney and house - swallows are a standing proof of a
change of habit since chimneys and houses were built, and
in America this change has taken place within about three
hundred years. Thread and worsted are now used in many
nests instead of wool and horsehair, and the jackdaw shows
an affection for the church steeple, which can hardly be
explained by instinct. In the more thickly populated parts
of the United States the Baltimore Oriole uses all sorts of
pieces of string, skeins of silk, or the gardener's bass, to weave
into its fine pensile nest, instead of the single hairs and vege-
table fibres it has painfully to seek in wilder regions ; and,
as already stated, Wilson, a most careful observer, believes
that it improves in neskbuilding by practice — the older birds
making the best nests. More recently, Dr. Abbott, the well-
known American naturalist, has studied the nests of the
Baltimore Oriole. He found that, away from the habitations
of man, the orioles built concealing nests ; but in villages
and cities, on the other hand, where they were in no special
danger from predatory hawks (or more probably from snakes)

v THE PHILOSOPHY OF BIRDS' NESTS 115

the nests were built comparatively open, so that the bird
within was not concealed.1 The purple martin takes posses-
sion of empty gourds or small boxes, stuck up for its reception
in almost every village and farm in America ; and several
of the American wrens will also build in cigar boxes, with a
small hole cut in them, if placed in a suitable situation. The
orchard oriole of the United States offers us an excellent
example of a bird which modifies its nest according to circum-
stances. When built among firm and stiff branches the nest
is very shallow, but if, as is often the case, it is suspended
from the slender twigs of the weeping willow, it is made
much deeper, so that when swayed about violently by the
wind the young may not tumble out. It has been observed
also that the nests built in the warm Southern States are
much slighter and more open in texture than those in the
colder regions of the north. Our own house-sparrow equally
well adapts himself to circumstances. When he builds in
trees, as he, no doubt, always did originally, he constructs a
well-made domed nest, perfectly fitted to protect his young
ones ; but when he can find a convenient hole in a building or
among thatch, or in any well-sheltered place, he takes much
less trouble, and forms a very loosely-built nest.

Professor Jeitteles of Vienna has described various forms of
nests of Hirundo urbica adapted to different situations, some
having the form of a semi-ellipsoid placed vertically, with the
entrance at one side, others being three-quarters of a sphere,
with the entrance in the centre. A nest of Hirundo rustica
was also observed supported on an iron hook in a wall, but
not itself touching the wall. It was quite hemispherical, like
that of a blackbird, a form common in England, whereas the
usual form on the Continent is that of a .quarter of a
sphere.2

The following case of a recent change of habit in nest-
building was communicated to me by Mr. Henry Reeks in
1870 : "Thirty years ago, and perhaps less, the herring-gulls
used to breed on some inland rocks in a large lake called

1 Popular Science Monthly, vol. vi. p. 481. Quoted by Vice-President
E. S. Morse, in Address to American Association for Advancement of Science
at Buffalo, N.Y., August 1876.

8 Ornithologischer Verein in Wien. Mitthelungen des Ausschusses, No. 3,
12 Juli 1876. See also Seebohm's British Birds, vol. ii. p. 174.

116 NATURAL SELECTION v

'Parsons Pond,' in Newfoundland, which is separated from
the sea only by a high pebbly beach. Within the period
above stated high tides and heavy seas have shifted the course
of the brook flowing from the lake into the sea, and caused a
greater, and consequently a more rapid fall of fresh water,
which has so shallowed that part of the lake where the gulls
were in the habit of breeding that it was no longer safe to
build on rocks easily accessible to their common enemy, the
fox. They therefore betook themselves to some neighbouring
spruce and balsam firs not much over a hundred yards distant
from their old breeding station." Audubon also notes a
similar change of habit, some herring-gulls building their nests
in spruce-trees on an island in the Bay of Fundy, where they
had formerly built on the ground.

A curious example of a recent change of habits has oc-
curred in Jamaica. Previous to 1854 the palm swift
(Tachornis phoenicobea) inhabited exclusively the palm trees
in a few districts in the island. A colony then established
themselves in two cocoa-nut palms in Spanish Town, and
remained there till 1857, when one tree was blown down and
the other stripped of its foliage. Instead of now seeking out
other palm trees the swifts drove out the swallows who built
in the piazza of the House of Assembly, and took possession
of it, building their nests on the tops of the end walls and at
the angles formed by the beams and joists, a place which they
continue to occupy in considerable numbers. It is remarked
that here they form their nest with much less elaboration than
when built in the palms, probably from being less exposed.

But perfection of structure and adaptation to purpose are
not universal characteristics of birds' nests, since there are
decided imperfections in the nesting of many birds which are
quite compatible with our present theory, but are hardly so
with that of instinct, which is supposed to be infallible. The
passenger pigeon of America often crowds the branches with
its nests till they break, and the ground is strewn with
shattered nests, eggs, and young birds. Books' nests are
often so imperfect that during high winds the eggs fall out ;
but the window-swallow is the most unfortunate in this re-
spect, for White, of Selborne, informs us that he has seen them
build, year after year, in places where their nests are liable

v THE PHILOSOPHY OF BIRDS' NESTS 117

to be washed away by a heavy rain and their young ones
destroyed.

Conclusion

A fair consideration of all these facts will, I think, fully
support the statement with which I commenced, and show
that the chief mental faculties exhibited by birds in . the con-
struction of their nests are the same in kind as those mani-
fested by mankind in the formation of their dwellings. These
are, essentially, imitation, and a slow and partial adaptation
to new conditions. To compare the work of birds with the
highest manifestations of human art and science is totally
beside the question. I do not maintain that birds are gifted
with reasoning faculties at all approaching in variety and
extent to those of man. I simply hold that the phenomena
presented by their mode of building their nests, when fairly
compared with those exhibited by the great mass of mankind
in building their houses, indicate no essential difference in the
kind or nature of the mental faculties employed. If instinct
means anything, it means the capacity to perform some com-
plex act without teaching or experience. It implies not only
innate ideas but innate knowledge of a very definite kind, and,
if established, would overthrow Mr. Mill's sensationalism and
all the modern philosophy of experience. That the existence
of true instinct may be established in other cases is not
impossible ; but in the particular instance of birds' nests, which
is usually considered one of its strongholds, I cannot find a
particle of evidence to show the existence of anything beyond
those lower reasoning and imitative powers which animals
are universally admitted to possess.

VI

A THEORY OF BIRDS' NESTS, SHOWING THE RELATION OF

CERTAIN DIFFERENCES OF COLOUR IN FEMALE BIRDS

TO THEIR MODE OF NIDIFICATION 1

THE habit of forming a more or less elaborate structure for
the reception of their eggs and young must undoubtedly be
looked upon as one of the most remarkable and interesting
characteristics of the class of birds. In other classes of verte-
brate animals, such structures are few and exceptional, and
never attain to the same degree of completeness and beauty.
Birds' nests have, accordingly, attracted much attention, and
have furnished one of the stock arguments to prove the exist-
ence of a blind but unerring instinct in the lower animals.
The very general belief that every bird is enabled to build its
nest, not by the ordinary faculties of observation, memory,
and imitation, but by means of some innate and mysterious im-
pulse, has had the bad effect of withdrawing attention from the
very evident relation that exists between the structure, habits,
and intelligence of birds, and the kind of nests they construct.

In the preceding essay I have detailed several of these
relations, and they teach us that a consideration of the
structure, the food, and other specialities of a bird's existence
will give a clue, and sometimes a very complete one, to the
reason why it builds its nest of certain materials, in a definite
situation, and in a more or less elaborate manner.

I now propose to consider the question from a more general
point of view, and to discuss its application to some important
problems in the natural history of birds.

1 Published in the Journal of Travel and Natural History, No. 2 ;
reprinted in Contributions, etc., with considerable additions and corrections.

vi A THEORY OF BIRDS' NESTS 119

Changed Conditions and persistent Habits as influencing
Nidification

Besides the causes above alluded to, there are two other
factors whose effect in any particular case we can only vaguely
guess at, but which must have had an important influence in
determining the existing details of nidification. These are —
changed conditions of existence, whether internal or external,
and the influence of hereditary or imitative habit ; the first
inducing alterations in accordance with changes of organic
structure, of climate, or of the surrounding fauna and flora ;
the other preserving the peculiarities so produced, even when
changed conditions render them no longer necessary. Many
facts have been already given which show that birds do adapt
their nests to the situations in which they place them, and the
adoption of eaves, chimneys, and boxes by swallows, wrens,
and many other birds, shows that they are always ready to
take advantage of changed conditions. It is probable, there-
fore, that a permanent change of climate would cause many
birds to modify the form or materials of their abodes, so as
better to protect their young. The introduction of new
enemies to eggs or young birds might introduce many alter-
ations tending to their better concealment. A change in the
vegetation of a country would often necessitate the use of
new materials. So, also, we may be sure, that as a species
slowly became modified in any external or internal characters,
it would necessarily change in some degree its mode of build-
ing. This effect would be produced by modifications of the
most varied nature ; such as the power and rapidity of flight,
which must often determine the distance to which a bird will
go to obtain materials for its nest ; the capacity of sustaining
itself almost motionless in the air, which must sometimes
determine the position in which a nest can be built; the
strength and grasping power of the foot in relation to the
weight of the bird, a power absolutely essential to the con-
structor of a delicately -woven and well -finished nest; the
length and fineness of the beak, which has to be used like
a needle in building the best textile nests ; the length and
mobility of the neck, which is needful for the same purpose ;
the possession of a salivary secretion like that used in the

120 NATURAL SELECTION vi

nests of many of the swifts and swallows, as well as that of
the song-thrush — peculiarities of habits which ultimately
depend on structure, and which often determine the material
most frequently met with or most easily to be obtained.
Modifications in any of these characters would necessarily
lead either to a change in the materials of the nest, or in the
mode of combining them in the finished structure, or in the
form or position of that structure.

During all these changes, however, certain specialities of
nest-building would continue for a shorter or a longer time
after the causes which had necessitated them had passed
away. Such records of a vanished past meet us everywhere,
even in man's works, notwithstanding his boasted reason.
Not only are the main features of Greek architecture mere
reproductions in stone of what were originally parts of a
wooden building, but our modern copyists of Gothic archi-
tecture often build solid buttresses capped with weighty
pinnacles to support a wooden roof which has no outward
thrust to render them necessary; and even think they
ornament their buildings by adding sham spouts of carved
stone, while modern waterpipes, stuck on without any attempt
at harmony, do the real duty. So, when railways superseded
coaches, it was thought necessary to build the first-class
carriages to imitate a number of coach-bodies joined together;
and the arm-loops for each passenger to hold on by, which
were useful when bad roads made every journey a succession
of jolts and lurches, were continued on our smooth macadam-
ised mail-routes, and, still more absurdly, remain to this day J
in our railway carriages, the relic of a kind of locomotion we
can now hardly realise. Another good example is to be seen
in our boots. When elastic sides came into fashion Ave had
been so long used to fasten them with buttons or laces, that
a boot without either looked bare and unfinished, and accord-
ingly the makers often put on a row of useless buttons or
imitation laces, because habit rendered the appearance of
them necessary to us. It is universally admitted that the
habits of children and of savages give us the best clue to the
habits and mode of thought of animals ; and every one must
have observed how children at first imitate the actions of
1 Since this was written they have generally been disused.

vi A THEORY OF BIRDS' NESTS 121

their elders, without any regard to the use or applicability of
the particular acts. So, in savages, many customs peculiar to
each tribe are handed down from father to son merely by the
force of habit, and are continued long after the purpose which
they originally served has ceased to exist. With these and a
hundred similar facts everywhere around us, we may fairly
impute much of what we cannot understand in the details of
Bird- Architecture to an analogous cause. If we do not do so,
we must assume either that birds are guided in every action
by pure reason to a far greater extent than men are, or that
an infallible instinct leads them to the same result by a
different road. The first theory has never, that I am aware
of, been maintained by any author, and I have already shown
that the second, although constantly assumed, has never been
proved, and that a large body of facts is entirely opposed to
it. One of my critics has, indeed, maintained that I admit
" instinct " under the term " hereditary habit " ; but the
whole course of my argument shows that I do not do so.
Hereditary habit is, indeed, the same as instinct when the
term is applied to some simple action dependent upon a
peculiarity of structure which is hereditary ; as when the
descendants of tumbler pigeons tumble, and the descendants
of pouter pigeons pout. In the present case, however, I
compare it strictly to the hereditary, or more properly, per-
sistent or imitative, habits of savages, in building their
houses as their fathers did. Imitation is a lower faculty
than invention. Children and savages imitate before
they originate ; birds, as well as all other animals, do the
same.

The preceding observations are intended to show that the
exact mode of nidification of each species of bird is probably
the result of a variety of causes, which have been continually
inducing changes in accordance with changed organic or
physical conditions. The most important of these causes
seem to be, in the first place, the structure of the species,
and, in the second, its environment or conditions of existence.
Now, we know that every one of the characters or conditions
included under these two heads is variable. We have seen
that, on the large scale, the main features of the nest built by
each group of birds bears a relation to the organic structure

122 NATURAL SELECTION vi

. _ — , ^

of that group, and we have, therefore, a right to infer that as
structure varies, the nest will vary also in some particular
corresponding to the changes of structure. We have seen
also that birds change the position, the form, and the con-
struction of their nest whenever the available materials or
the available situations vary naturally or have been altered
by man ; and we have, therefore, a right to infer that similar
changes have taken place when, by a natural process, external
conditions have become in any way permanently altered. We
must remember, however, that all these factors are very stable
during many generations, and only change at a rate com-
mensurate with those of the great physical features of the
earth as revealed to us by geology ; and we may, therefore,
infer that the form and construction of nests, which we have
shown to be dependent on them, are equally stable. If,
therefore, we find less important and more easily modified
characters than these so correlated with peculiarities of
nidification as to indicate that one is probably the cause of
the other, we shall be justified in concluding that these
variable characters are dependent on the mode of nidification,
and not that the form of the nest has been determined by
these variable characters. Such a correlation I am now
about to point out.

Classification of Nests

For the purpose of this inquiry it is necessary to group
nests into two great classes, without any regard to their most
obvious differences or resemblances, but solely looking to the
fact of whether the contents (eggs, young, or sitting bird) are
hidden or exposed to view. In the first class we place all
those in which the eggs and young are completely hidden,
no matter whether this is effected by an elaborate covered
structure, or by depositing the eggs in some hollow tree or
burrow underground. In the second, we group all in which
the eggs, young, and sitting bird are exposed to view, no
matter whether there is the most beautifully formed nest or
none at all. Kingfishers, which build almost invariably in
holes in banks; woodpeckers and parrots, which build in
hollow trees; the Icteridae of America, which all make
beautiful covered and suspended nests ; and our own wren,
which builds a domed nest— are examples of the former;

vi A THEORY OF BIRDS' NESTS 123

while our thrashes, warblers, and finches, as well as the crow-
shrikes, chatterers, and tanagers of the tropics, together with all
raptorial birds and pigeons, and a vast number of others in
every part of the world, all adopt the latter mode of building.

It will be seen that this division of birds, according to
their nidification, bears little relation to the character of the
nest itself. It is a functional not a structural classification.
The most rude and the most perfect specimens of bird-
architecture are to be found in both sections. It has, how-
ever, a certain relation to natural affinities, for large groups of
birds, undoubtedly allied, fall into one or the other division
exclusively. The species of a genus or of a family are rarely
divided between the two primary classes, although they are
frequently divided between the two very distinct modes of
nidification that exist in the first of them.

All the Scansorial or climbing, and most of the Fissirostral
or wide-gaped birds, for example, build concealed nests ; and
in the latter group the two families which build open nests,
the swifts and the goatsuckers, are undoubtedly very widely
separated from the other families with which they are asso-
ciated in our classifications.1 The tits vary much in their
mode of nesting, some making open nests concealed in a hole,
while others build domed or even pendulous covered nests,
but they all come under the same class. Starlings vary in a
similar way. The talking mynahs, like our own starlings,
build in holes, the glossy starlings of the East (of the genus
Calornis) form a hanging covered nest, while the genus
Sturnopastor builds in a hollow tree. One of the most
striking cases in which one family of birds is divided between
the two classes is that of the finches ; for while most of the
European species build exposed nests, many of the Australian
finches make them dome-shaped.

Sexual differences of Colour in Birds

Turning now from the nests to the creatures who make
them, let us consider birds themselves from a somewhat
unusual point of view, and form them into separate groups,

1 Recent research places the goatsuckers nearest to (though still far
from) the owls, while swifts are again brought nearer to the swallows.
Dr. R. W. Shufeldt in Journ. of the Linn. Soc., vol. xx. Zoology, p. 383.

124 NATURAL SELECTION vi

•»

according as both sexes, or the males only, are adorned with
conspicuous colours.

The sexual differences of colour and plumage in birds are
very remarkable, and have attracted much attention ; and, in
the case of polygamous birds, have been explained by Mr.
Darwin's principle of sexual selection. We may, perhaps,
understand how male pheasants and grouse have acquired
their more brilliant plumage and greater size by the continual
rivalry of the males both in strength and beauty ; but this
theory does not throw any light on the causes which have
made the female toucan, bee -eater, parroquet, macaw, and
tit in almost every case as gay and brilliant as the male,
while the gorgeous chatterers, manakins, tanagers, and birds
of paradise, as well as our own blackbird, have mates so dull
and inconspicuous that they can hardly be recognised as
belonging to the same species.

The Law which connects the Colours of Female Birds
with the mode of Nidification

The above-stated anomaly can, however, now be explained
by the influence of the mode of nidification, since, with very
few exceptions, I find it to be the rule — that when both
sexes are of strikingly gay and conspicuous colours the nest is of the
first class, or such as to conceal the sitting birds ; while, whenever
the male is gay and conspicuous and the nest is open so as to expose
the sitting bird to view, the female is of dull or obscure colours. I
will now proceed to indicate the chief facts that support this
statement, and will afterwards explain the manner in which I
conceive the relation has been brought about.

We will first consider those groups of birds in which the
female is gaily or at least conspicuously coloured, and is in
most cases exactly like the male.

1. Kingfishers (Alcedinidse). In some of the most brilliant
species of this family the female exactly resembles the male ;
in others there is a sexual difference, but it rarely tends to
make the female less conspicuous. In some the female has a
coloured band across the breast, which is wanting in the male,
as in the beautiful blue and white Halcyon diops of Ternate.
In others the band is rufous in the female, as in several of the
American species ; while in Dacelo gaudichaudii, and others of

vi A THEORY OF BIRDS' NESTS 125

the same genus, the tail of the female is rufous, while that of
the male is blue. In most kingfishers the nest is in a deep
hole in the ground ; in Tanysiptera it is said to be a hole
in the nests of termites, or sometimes in crevices under over-
hanging rocks.

2. Motmots (Momotidse). In these showy birds the sexes
are exactly alike, and the nest in a hole under ground.

3. Puff-birds (Bucconidse). These birds are often gaily
coloured; some have coral -red bills; the sexes are exactly
alike, and the nest is in a hole in sloping ground.

4. Trogons (Trogonidse). In these magnificent birds the
females are generally less brightly coloured than the males, but
are yet often gay and conspicuous. The nest is in a hole of a tree.

5. Hoopoes (Upupidse). The barred plumage and long
crests of these birds render them conspicuous. The sexes are
exactly alike, and the nest is in a hollow tree.

6. Hornbills (Bucerotidae). These large birds have enor-
mous coloured bills, which are generally quite as well coloured
and conspicuous in the females. Their nests are always in
hollow trees, where the female is entirely concealed.

7. Barbets (Capitonidse). These birds are all very gaily-
coloured, and, what is remarkable, the most brilliant patches
of colour are disposed about the head and neck, and are very
conspicuous. The sexes are exactly alike, and the nest is in
a hole of a tree.

8. Toucans (Rhamphastidae). These fine birds are coloured
in the most conspicuous parts of their body, especially on the
large bill, and on the upper and lower tail coverts, which are
crimson, white, or yellow. The sexes are exactly alike, and
they always build in a hollow tree.

9. Plaintain-eaters (Musophagidae). Here again the head
and bill are most brilliantly coloured in both sexes, and the
nest is in a hole of a tree.

10. Ground cuckoos (Centropus). These birds are often
of conspicuous colours, and are alike in both sexes. They
build a domed nest.

11. Woodpeckers (Picidae). In this family the females
often differ from the males in having a yellow or white,
instead of a crimson crest, but are almost as conspicuous.
They all nest in holes in trees.

126 NATURAL SELECTION % vi

12. Parrots (Psittaci). In this great tribe, adorned with
the most brilliant and varied colours, the rule is that the
sexes are precisely alike, and this is the case in the most
gorgeous families, the lories, the cockatoos, and the macaws ;
but in some there is a sexual difference of colour to a
slight extent. All build in holes, mostly in trees, but some-
times in the ground, or in white ants' nests. In the single
case in which the nest is exposed, that of the Australian
ground parrot, Pezoporus formosus, the bird has lost the gay
colouring of its allies, and is clothed in sombre and completely
protective tints of dusky green and black.

13. Gapers (Eurylsemidae). In these beautiful Eastern
birds, somewhat allied to the American chatterers, the sexes
are exactly alike, and are adorned with the most gay and con-
spicuous markings. The nest is a woven structure, covered over,
and suspended from the extremities of branches over water.

14. Pardalotus (Ampelidae). In these Australian birds
the females differ from the males, but are often very con-
spicuous, having brightly -spotted heads. Their nests are
sometimes dome shaped, sometimes in holes of trees, or in
burrows in the ground.

15. Tits (Paridse). These little birds are always pretty, and
many (especially among the Indian species) are very conspicuous.
They always have the sexes alike, a circumstance very unusual
among the smaller gaily-coloured birds of our own country.
The nest is always covered over or concealed in a hole.

16. Nuthatches (Sitta). Often very pretty birds, the
sexes alike, and the nest in a hole.

17. (SitteUa). The female of these Australian nut-
hatches is often the most conspicuous, being white and black
marked. The nest is, according to Gould, " completely con-
cealed among upright twigs connected together."

18. Creepers (Climacteris). In these Australian creepers
the sexes are alike, or the female most conspicuous, and the
nest is in a hole of a tree.

19. Estrelda, Amadina. In these genera of Eastern and
Australian finches the females, although more or less different
from the males, are still very conspicuous, having a red rump,
or being white spotted. They differ from most others of the
family in building domed nests.

vi A THEORY OF BIRDS' NESTS 127

20. Certhiola. In these pretty little American creepers
the sexes are alike, and they build a domed nest.

21. Mynahs (Sturnidae). These showy Eastern starlings
have the sexes exactly alike. They build in holes of trees.

22. Calornis (Sturnidse). These brilliant metallic starlings
have no sexual differences. They build a pensile covered nest.

23. Hangnests (Icteridse). The red or yellow and black
plumage of most of these birds is very conspicuous, and is
exactly alike in both sexes. They are celebrated for their
fine purse-shaped pensile nests.

It will be seen that this list comprehends six important
families of Fissirostres, four of Scansores, the Psittaci, and
several genera, with three entire families of Passeres, com-
prising about twelve hundred species, or about one-seventh of
all known birds.

The cases in which, whenever the male is gaily coloured,
the female is much less gay or quite inconspicuous are ex-
ceedingly numerous, comprising, in fact, almost all the bright- '
coloured Passeres, except those enumerated in the preceding
class. The following are the most remarkable : —

1. Chatterers (Cotingidse). These comprise some of the
most gorgeous birds in the world, vivid blues, rich purples,
and bright reds being the most characteristic colours. The
females are always obscurely tinted, and are often of a
greenish hue, not easily visible among the foliage.

2. Manakins (Pipridse). These elegant birds, whose caps
or crests are of the most brilliant colours, are usually of a
sombre green in the female sex.

3. Tanagers (Tanagridse). These rival the chatterers in
the brilliancy of their colours, and are even more varied. The
females are generally of plain and sombre hues, and always
less conspicuous than the males.

4. Sugar-birds (Coerebidse). The males are a beautiful
blue ; the females green.

5. Pheasants (Phasianidse). These include some of the
most brilliant and gorgeously coloured birds in the world,
such as the peacock, gold and silver pheasants, fire-backed
pheasants, and many others ; but the females are always com-
paratively dull coloured, and generally of highly protective tints.

NATURAL SELECTION

In the extensive families of the warblers (Sylviadae),
thrushes (Turdidae), flycatchers (Muscicapidse), and shrikes
(Laniadee), a considerable proportion of the species are beauti-
fully marked with gay and conspicuous tints, but in every
case the females are less gay, and are most frequently of the
very plainest and least conspicuous hues. Now, throughout
the whole of these families the nest is open, and I am not aware of
a single instance in which any one of these birds builds a
domed nest, or places it in a hole of a tree, or under ground, or in
any place where it is effectually concealed.

In considering the question we are now investigating, it is
not necessary to take into account the larger and more power-
ful birds, because they seldom depend much on concealment
to secure their safety. In the raptorial birds bright colours
are as a rule absent ; and their structure and habits are such
as not to require any special protection for the female. The
larger waders are sometimes very brightly coloured in both
sexes ; but they are probably little subject to the attacks of
enemies, since the scarlet ibis, the most conspicuous of birds,
exist in immense quantities in South America. In game birds
and water-fowl, however, the females are often very plainly
coloured, when the males are adorned with brilliant hues ;
and the abnormal family of the Megapodidee offers us the in-
teresting fact of an identity in the colours of the sexes (which
in Megacephalon and Talegalla are somewhat conspicuous), in
conjunction with the habit of not sitting on the eggs at all.

What the Fads Teach us

Taking the whole body of evidence here brought forward,
embracing as it does almost every group of bright-coloured
birds, it will, I think, be admitted that the relation between
the two series of facts in the colouring and nidification of
birds has been sufficiently established. There are, it is true,
a few apparent and some real exceptions, which I shall con-
sider presently ; but they are too few and unimportant to
weigh much against the mass of evidence on the other side,
and may for the present be neglected. Let us then consider
what we are to do with this unexpected set of correspondences
between groups of phenomena which, at first sight, appear so
disconnected. Do they fall in with any other groups of

A THEORY OF BIRDS' NESTS

natural phenomena 1 Do they teach us anything of the way
in which nature works, and give us any insight into the
causes which have brought about the marvellous variety, and
beauty, and harmony of living things? I believe we can
answer these questions in the affirmative ; and I may mention,
as a sufficient proof that these are not isolated facts, that I
was first led to see their relation to each other by the study
of an analogous though distinct set of phenomena among in-
sects, that of protective resemblance and " mimicry."

On considering this remarkable series of corresponding
facts, the first thing we are taught by them seems to be, that
there is no incapacity in the female sex among birds to receive
the same bright hues and strongly contrasted tints with which
their partners are so often decorated, since whenever they are
protected and concealed during the period of incubation they
are similarly adorned. The fair inference is, that it is chiefly
due to the absence of protection or concealment during this
important epoch, that gay and conspicuous tints are withheld
or left undeveloped. The mode in which this has been effected
is very intelligible, if we admit the action of natural and
sexual selection. It would appear from the numerous cases
in which both sexes are adorned with equally brilliant colours
(while both sexes are rarely armed with equally developed
offensive and defensive weapons when not required for indi-
vidual safety), that the normal action of " sexual selection " or
of other unknown causes, is to develop colour and beauty in
both sexes, by the preservation and multiplication of all
varieties of colour in either sex which are pleasing to the
other. Several very close observers of the habits of animals
have assured me that male birds and quadrupeds do often
take very strong likes and dislikes to individual females, and
we can hardly believe that the one sex (the female) can have
a general taste for colour while the other has no such taste.
However this may be, the fact remains, that in a vast number
of cases the female acquires as brilliant and as varied colours
as the male, and therefore most probably acquires them in the
same way as the male does — that is, either because the
colour is useful to it, or is correlated with some useful varia-
tion, or is pleasing to the other sex. The only remaining
supposition is that it is transmitted from the other sex, with-
K

130 NATURAL SELECTION vi

out being of any use. From the number of examples above
adduced of bright colours in the female, this would imply that
colour-characters acquired by one sex are generally (but not
necessarily) transmitted to the other. If this be the case it
will, I think, enable us to explain the phenomena, even if we
do not admit that the male bird is ever influenced in the
choice of a mate by her more gay or perfect plumage.

The female bird, while sitting on her eggs in an uncovered
nest, is much exposed to the attacks of enemies, and any
modification of colour which rendered her more conspicuous
would often lead to her destruction and that of her offspring.
All variations of colour in this direction in the female would
therefore sooner or later be eliminated, while such modifications
as rendered her inconspicuous, by assimilating her to sur-
rounding objects, as the earth or the foliage, would, on the
whole, survive the longest, and thus lead to the attainment
of those brown or green and inconspicuous tints, which form
the colouring (of the upper surface at least) of the vast
majority of female birds which sit upon open nests.

This does not imply, as some have thought, that all female
birds were once as brilliant as the males. The change has
been a very gradual one, generally dating from the origin of
genera or of larger groups, but there can be no doubt that
the remote ancestry of birds having great sexual differences
of colour were nearly or quite alike, sometimes (perhaps in
most cases) more nearly resembling the female, but occasion-
ally perhaps being nearer what the male is now. The young
birds (which usually resemble the females) will probably give
some idea of this ancestral type, and it is well known that
the young of allied species and of different sexes are often
undistinguishable.

Colour more variable than Structure or Habits, and therefore the

Character which has generally been Modified
At the commencement of this essay I have endeavoured
to prove that the characteristic differences and the essential
features of birds' nests are dependent on the structure of the
species and upon the present and past conditions of their
existence. Both these factors are more important and less
variable than colour j and we must therefore conclude that in

vi A THEORY OF BIRDS' NESTS 131

most cases the mode of nidification (dependent on structure
and environment) has been the cause, and not the effect, of
the similarity or differences of the sexes as regards colour.
When the confirmed habit of a group of birds was to build
their nests in holes of trees like the toucans, or in holes in
the ground like the kingfishers, the protection the female thus
obtained, during the important and dangerous time of incuba-
tion, placed the two sexes on an equality as regards exposure
to attack, and allowed " sexual selection," or any other cause,
to act unchecked in the development of gay colours and con-
spicuous markings in both sexes.

When, on the other hand (as in the tanagers and flycatchers),
the habit of the whole group was to build open cup-shaped
nests in more or less exposed situations, the production of
colour and marking in the female, by whatever cause, was
continually checked by its rendering her too conspicuous, while
in the male it had free play, and developed in him the most
gorgeous hues. This, however, was not perhaps universally
the case ; for where there was more than usual intelligence
and capacity for change of habits, the danger the female was
exposed to by a partial brightness of colour or marking might
lead to the construction of a concealed or covered nest, as in
the case of the tits and hangnests. When this occurred, a
special protection to the female would be no longer necessary;
so that the acquisition of colour and the modification of the
nest might in some cases act and reactj on each other and
attain their full development together.

Exceptional Cases confirmatory of the above Explanation
There exist a few very curious and anomalous facts in the
natural history of birds, which fortunately serve as crucial
tests of the truth of this mode of explaining the inequalities
of sexual coloration. It has been long known that in some
species the males either assisted in, or wholly performed, the
act of incubation. It has also been often noticed that in
certain birds the usual sexual differences were reversed, the
male being the more plainly coloured, the female more gay
and often larger. I am not, however, aware that these two
anomalies had ever been supposed to stand to each other in
the relation of cause and effect, till I adduced them in support

182 NATURAL SELECTION vi

of my views of the general theory of protective adaptation.
Yet it is undoubtedly the fact that in the best known cases
in which the female bird is more conspicuously coloured than
the male, it is either positively ascertained that the latter
performs the duties of incubation, or there are good reasons
for believing such to be the case. The most satisfactory
example is that of the Gray Phalarope (Phalaropus fulicarius),
the sexes of which are alike in winter, while in summer the
female instead of the male takes on a gay and conspicuous
nuptial plumage ; but the male performs the duties of incubation,
sitting upon the eggs, which are laid upon the bare ground.

In the dotterel! (Eudromias morinellus) the female is
larger and more brightly coloured than the male ; and here,
also, it is almost certain that the latter sits upon the eggs.
The turnices of India also have the female larger and often
more brightly coloured ; and Mr. Jerdon states, in his Birds
of India, that the natives report that, during the breeding
season, the females desert their eggs and associate in flocks,
while the males are employed in hatching the eggs. In the
few other cases in which the females are more brightly
coloured, the habits are not accurately known. The case of
the ostriches and emeus will occur to many as a difficulty,
for here the male incubates, but is not less conspicuous than
the female ; but there are two reasons why the case does not
apply : the birds are too large to derive any safety from
concealment ; from enemies which would devour the eggs
they can defend themselves by force, while to escape from
their personal foes they trust to speed.

We find, therefore, that a very large mass of facts relating
to the sexual coloration and the mode of nidification of birds,
including some of the most extraordinary anomalies to be
found in their natural history, can be shown to have an inter-
dependent relation to each other, on the simple principle of
the need of greater protection to that parent which performs
the duties of incubation. Considering the very imperfect
knowledge we possess of the habits of most extra-European
birds, the exceptions to the prevalent rule are few, and gene-
rally occur in isolated species or in small groups ; while several
apparent exceptions can be shown to be really confirmations
of the law.

vi A THEORY OF BIRDS' NESTS 133

Real or apparent Exceptions to the Law stated at page 124

The only marked exceptions I have been able to discover
are the following —

1. King crows (Dicrourus). These birds are of a glossy
black colour, with long forked tails. The sexes present no
difference, and they build open nests. This apparent excep-
tion may probably be accounted for by the fact that these
birds do not need the protection of a less conspicuous colour.
They are very pugnacious, and often attack and drive away
crows, hawks, and kites ; and as they are semi-gregarious in
their habits, the females are not likely to be attacked while
incubating.

2. Orioles (Oriolidse). The true orioles are very gay birds ;
the sexes are, in many Eastern species, either nearly or quite
alike, and the nests are open. This is one of the most serious
exceptions, but it is one that to some extent proves the rule ;
for in this case it has been noticed that the parent birds
display excessive care and solicitude in concealing the nest
among thick foliage, and in protecting their offspring by in-
cessant and anxious watching. This indicates that the want
of protection consequent on the bright colour of the female
makes itself felt, and is obviated by an increased development
of the mental faculties.

3. Ground thrushes (Pittidse). These elegant and brilliantly-
coloured birds are generally alike in both sexes, and build an
open nest. It is curious, however, that this is only an ap-
parent exception, for almost all the bright colours are on the
under surface, the back being usually olive-green or brown,
and the head black, with brown or whitish stripes, all which
colours would harmonise with the foliage, sticks, and roots
which surround the nest, built on or near the ground, and
thus serve as a protection to the female bird.

4. Grallina Australis. This Australian bird is of strongly
contrasted black and white colours. The sexes are exactly
alike, and it builds an open clay nest in an exposed situation
on a tree. This appears to be a most striking exception, but
I am by no means sure that it is so. We require to know
what tree it usually builds on, the colour of the bark or of
the lichens that grow upon it, the tints of the ground, or of

134 NATURAL SELECTION > vi

other surrounding objects, before we can say that the bird,
when sitting on its nest, is really conspicuous. It has been
remarked that small patches of white and black blend at a
short distance to form gray, one of the commonest tints of
natural objects.

5. Sunbirds (Nectariniidse). In these beautiful little birds
the males only are adorned with brilliant colours, the females
being quite plain, yet they build covered nests in all the cases
in which the nidification is known. This is a negative rather
than a positive exception to the rule, since there may be other
causes besides the need for protection which prevent the
female acquiring the gay colours of her mate, and there is one
curious circumstance which tends to elucidate it. The male
of Leptocoma zeylanica is said to assist in incubation. It is
possible, therefore, that the group may originally have used
open nests, and some change of conditions, leading the male
bird to sit, may have been followed by the adoption of a domed
nest. This is, however, the most serious exception I have yet
found to the general rule.

6. Superb warblers (Maluridse). The males of these little
birds are adorned with the most gorgeous colours, while the
females are very plain, yet they make domed nests. It is to
be observed, however, that the male plumage is nuptial
merely, and is retained for a very short time ; the rest of
the year both sexes are plain alike. It is probable, there-
fore, that the domed nest is for the protection of these
delicate little birds against the rain, and that there is some
unknown cause which has led to the development of colour
in the males only.

There is one other case which at first sight looks like an
exception, but which is far from being one in reality, and
deserves to be mentioned. In the beautiful waxwing (Bom-
bycilla garrula) the sexes are very nearly alike, and the
elegant red wax tips to the wing-feathers are nearly, and
sometimes quite, as conspicuous in the female as in the male.
Yet it builds an open nest, and a person looking at the bird
would say it ought, according to my theory, to cover its nest.
But it is, in reality, as completely protected by its coloration
as the most plainly coloured bird that flies. It breeds only
in very high latitudes, and the nest, placed in fir-trees, is

vi A THEORY OF BIRDS' NESTS 135

formed chiefly of fir-twigs and lichens. Now the delicate
gray and ashy and purplish hues of the head and back, to-
gether with the yellow of the wings and tail, are tints that
exactly harmonise with the colours of fir leaves, bark, and
lichens, while the brilliant red wax tips exactly represent the
crimson fructification of the common lichen, Cladonia cocci-
fera. When sitting on its nest, therefore, the female bird
will exhibit no colours that are not common to the materials
by which it is surrounded ; and the several tints are distri-
buted in about the same proportions as they occur in nature.
At a short distance the bird would be undistinguishable from
the nest it is sitting on, or from a natural clump of lichens,
and will thus be completely protected.

I think I have now noticed all exceptions of any import-
ance to the law of dependence of sexual colour on modification.
It will be seen that they are very few in number, compared
with those which support the generalisation ; and in several
cases there are circumstances in the habits or structure of the
species that sufficiently explain them. It is remarkable also
that I have found scarcely any positive exceptions — that is,
cases of very brilliant or conspicuous female birds in which
the nest was not concealed. Much less can there be shown
any group of birds in which the females are all of decidedly
conspicuous colours on the upper surface, and yet sit in open
nests. The many cases in which birds of dull colours in both
sexes make domed or concealed nests do not, of course, affect
this theory one way or the other ; since its purpose is only
to account for the fact that brilliant females of brilliant
males are always found to have covered or hidden nests, while
obscure females of brilliant males almost always have open and
exposed nests. The fact that all classes of nests occur with
birds which are dull coloured in both sexes merely shows
that these dull colours serve to protect the parents at other
times than when sitting on the nest, the structure of which is
determined by the requirements of the offspring.

If the views here advocated are correct, as to the various
influences that have determined the specialities of every bird's
nest, and the general coloration of female birds, with their
action and reaction on each other, we can hardly expect to
find evidence more complete than that here set forth. Nature

136 NATURAL SELECTION ^ vi

is such a tangled web of complex relations, that a series of
correspondences running through hundreds of species, genera,
and families, in every part of the system, can hardly fail to
indicate a true casual connection ; and when, of the two
factors in the problem, one can be shown to be dependent on
the most deeply seated and the most stable facts of structure
and conditions of life, while the other is a character univer-
sally admitted to be superficial and easily modified, there can
be little doubt as to which is cause and which effect.

Various modes of Protection of Animals
But the explanation of the phenomenon here attempted
does not rest alone on the facts I have been able now to
adduce. In the essay on "Mimicry" it is shown how im-
portant a part the necessity for protection has played, in
determining the external form and coloration, and sometimes
even the internal structure of animals.

As illustrating this latter point, I may refer to the remark-
able hooked, branched, or star-like spiculae in many sponges,
which are believed to have the function chiefly of rendering
them unpalatable to other creatures. The Holothuridae or
sea -cucumbers possess a similar protection, many of them
having anchor-shaped spicules embedded in their skin, as the
Synapta ; while others (Cuviera squamata) are covered with a
hard calcareous pavement. Many of these are of a bright red
or purple colour, and are very conspicuous, while the allied
Trepang, or Beche-de-mer (Holothuria edulis), which is not
armed with any such defensive weapons, is of a dull sand or
mud colour, so as hardly to be distinguished from the sea-bed
on which it reposes. Many of the smaller marine animals are
protected by their almost invisible transparency, Avhile those
that are most brightly coloured will be often found to have a
special protection, either in stinging tentacles like Physalia,
or in a hard calcareous crust, as in the star-fishes.

Females of some Groups require and obtain more Protection
than the Males

In the struggle for existence incessantly going on, pro-
tection or concealment is one of the most general and most
effectual means of maintaining life ; and it is by modifications

vi A THEORY OF BIRDS' NESTS 137

of colour that this protection can be most readily obtained,
since no other character is subject to such numerous and
rapid variations. The case I have now endeavoured to illus-
trate is exactly analogous to what occurs among butterflies.
As a general rule, the female butterfly is of dull and incon-
spicuous colours, even when the male is most gorgeously
arrayed ; but when the species is protected from attack by a
disagreeable odour and taste, as in the Heliconidse, Danaidae
and Acrseidae, both sexes display the same or equally brilliant
hues. Among the species which gain a protection by imitat-
ing these, the very weak and slow-flying Leptalides resemble
them in both sexes, because both sexes alike require pro-
tection, while in the more active and strong-winged genera —
Papilio, Pieris, and Diadema — it is generally the females only
that mimic the protected groups, and in doing so often become
actually more gay and more conspicuous than the males, thus
reversing the usual and in fact almost universal characters of
the sexes. So, in the wonderful Eastern leaf-insects of the
genus Phyllium, it is the female only that so marvellously
imitates a green leaf ; and in all these cases the difference can
be traced to the greater need of protection for the female, on
whose continued existence, while depositing her eggs, the
safety of the race depends. In Mammalia and in reptiles,
however brilliant the colour may be, there is rarely any differ-
ence between that of the sexes, because the female is not
necessarily more exposed to attack than the male. It may, I
think, be looked upon as a confirmation of this view, that no
single case is known either in the above-named genera —
Papilio, Pieris, and Diadema — or in any other butterfly, of a
male alone mimicking one of the Danaidse or Heliconidaa
Yet the necessary colour is far more abundant in the males,
and variations always seem ready for any useful purpose.
This seems to depend on the general law that each species
and each sex can only be modified just as far as is absolutely
necessary for it to maintain itself in the struggle for existence,
not a step further. A male insect by its structure and habits
is less exposed to danger, and also requires less protection,
than the female. It cannot, therefore, alone acquire any
further protection through the agency of natural selection.
But the female requires some extra protection, to balance the

138 NATURAL SELECTION

greater danger to which she is exposed and her greater im-
portance to the existence of the species ; and this she always
acquires, in one way or another, through the action of natural
selection.

In his Origin of Species, fourth edition, p. 241, Mr. Darwin
recognises the necessity for protection as sometimes being a
cause of the obscure colours of female birds ; 1 but he does not
seem to consider it so very important an agent in modifying
colour as I am disposed to do. In the same paragraph (p.
240) he alludes to the fact of female birds and butterflies
being sometimes very plain, sometimes as gay as the males ;
but, apparently, considers this mainly due to peculiar laws of
inheritance, which sometimes continue acquired colour in the
line of one sex only, sometimes in both. Without denying
the action of such a law (which Mr. Darwin informs me he
has facts to support), I impute the difference, in the great
majority of cases, to the greater or less need of protection in
the female sex in these groups of animals.

This need was seen to exist a century ago by the Hon.
Daines Barrington, who, in the article already quoted (see p.
104), after alluding to the fact that singing birds are all small,
and suggesting (but I think erroneously) that this may have
arisen from the difficulty larger birds would have in conceal-
ing themselves if they called the attention of their enemies by
loud notes, goes on thus : " I should rather conceive it is for
the same reason no hen bird sings, because this talent would
be still more dangerous during incubation, which may possibly
also account for the inferiority in point of plumage." This is a
curious anticipation of the main idea on which this essay is
founded. It has been unnoticed for near a century, and my
attention was only recently called to it by Mr. Darwin himself.

Conclusion

To some persons it will perhaps appear that the causes to
which I impute so much of the external aspect of nature are
too simple, too insignificant, and too unimportant for such a
mighty Ayork. But I would ask them to consider that the
great object of all the peculiarities of animal structure is to
preserve the life of the individual, and to maintain the exist-
1 This passage is omitted in the sixth edition.

vi A THEORY OF BIRDS' NESTS 139

ence of the species. Colour has hitherto been too often looked
upon as something adventitious and superficial, something
given to an animal not to be useful to itself, but solely to
gratify man or even superior beings — to add to the beauty
and ideal harmony of nature. If this were the case, then, it
is evident that the colours of organised beings would be an
exception to most other natural phenomena. They would not
be the product of general laws, or determined by ever-chang-
ing external conditions ; and we must give up all inquiry into
their origin and causes, since (by the hypothesis) they are
dependent on a Will whose motives must ever be unknown to
us. But, strange to say, no sooner do we begin to examine
and classify the colours of natural objects, than we find that
they are intimately related to a variety of other phenomena,
and are, like them, strictly subordinated to general laws. I
have here attempted to elucidate some of these laws in the
case of birds, and have shown how the mode of nidification
has affected the colouring of the female sex in this group. I
have before shown to how great an extent, and in how many
ways, the need of protection has determined the colours of
insects, and of some groups of reptiles and mammalia, and I
would now call particular attention to the fact that the gay
tints of flowers, so long supposed to be a convincing proof that
colour has been bestowed for other purposes than the good of
its possessor, have been shown by Mr. Darwin to follow the
same great law of utility. Flowers do not often need pro-
tection, but very often require the aid of insects to fertilise
them, and maintain their reproductive powers in the greatest
vigour. Their gay colours attract insects, as do also their
sweet odours and honeyed secretions ; and that this is the
main function of colour in flowers is shown by the striking
fact that those flowers which can be perfectly fertilised by
the wind, and do not need the aid of insects, rarely or never
have gaily-coloured flowers.

This wide extension of the general principle of utility to
the colours of such varied groups, both in the animal and
vegetable kingdoms, compels us to acknowledge that the
" reign of law" has been fairly traced into this stronghold of
the advocates of special creation. And to those who oppose
the explanation now given of the various facts bearing upon

140 NATURAL SELECTION ^ vi

this subject, I would again respectfully urge that they must
grapple with the whole of the facts, not one or two of them
only. It will be admitted that, on the theory of evolution
and natural selection, a wide range of facts with regard to
colour in nature have been co-ordinated and explained. Until
at least an equally wide range of facts can be shown to be in
harmony with any other theory, we can hardly be expected
to abandon that which has already done such good service,
and which has led to the discovery of so many interesting
and unexpected harmonies among the most common (but
hitherto most neglected and least understood) of the phe-
nomena presented by organised beings.

VII

CREATION BY LAW1

AMONG the various criticisms that have appeared on Mr.
Darwin's celebrated Origin of Species, there is, perhaps,
none that will appeal to so large a number of well educated
and intelligent persons as that contained in the Duke of
Argyll's Reign of Law. The noble author represents the feel-
ings and expresses the ideas of that large class of persons who
take a keen interest in the progress of science in general,
and especially that of Natural History, but have never them-
selves studied nature in detail, or acquired that personal
knowledge of the structure of closely allied forms, — the
wonderful gradations from species to species and from group
to group, and the infinite variety of the phenomena of " varia-
tion " in organic beings, — which is absolutely necessary for
a full appreciation of the facts and reasonings contained in
Mr. Darwin's great work.

Nearly half of the Duke's book is devoted to an exposition
of his idea of " Creation by Law," and he expresses so clearly
what are his difficulties and objections as regards the theory
of " Natural Selection," that I think it advisable that they
should be fairly answered, and that his own views should be
shown to lead to conclusions .as hard to accept as any which
he imputes to Mr. Darwin.

The point on which the Duke of Argyll lays most stress
is, that proofs of Mind everywhere meet us in Nature, and
are more especially manifest wherever we find " contrivance "
or "beauty." He maintains that this indicates the constant

1 First published in the Quarterly Journal of Science, October 1868 ;
reprinted in Contributions, etc., with a few alterations and additions.

142 NATURAL SELECTION vn

supervision and direct interference of the Creator, and
cannot possibly be explained by the unassisted action of any
combination of laws. Now, Mr. Darwin's work has for its
main object to show that all the phenomena of living things,

all their wonderful organs and complicated structures, their

infinite variety of form, size, and colour, their intricate and
involved relations to each other, — may have been produced
by the action of a few general laws of the simplest kind, laws
which are in most cases mere statements of admitted facts.
The chief of these laws or facts are the following : —

1. The Law of Multiplication in Geometrical Progression. —
All organised beings have enormous powers of multiplication.
Even man, who increases slower than all other animals, could
under the most favourable circumstances double his numbers
every fifteen years, or a hundredfold in a century. Many
animals and plants could increase their numbers from ten to
a thousandfold every year.

2. The Law of Limited Populations. — The number of living
individuals of each species in any country, or in the whole
globe, is practically stationary; whence it follows that the
whole of this enormous increase must die off almost as fast
as produced, except only those individuals for whom room is
made by the death of parents. As a simple but striking
example, take an oak forest. Every oak will drop annually
many thousands of acorns, but till an old tree falls not one
of the millions of acorns produced can grow up into an oak.
They must die at various stages of growth.

3. The Law of Heredity, or Likeness of Offspring to their
Parents. — This is a universal, but not an absolute law. All
creatures resemble their parents in a high degree, and in the
majority of cases very accurately; so that even individual
peculiarities, of whatever kind, in the parents, are almost
always transmitted to some of the offspring.

4. The Law of Variation. — This is fully expressed by the
lines : —

" No being on this earthly ball,
Is like another, all in all. "

Offspring resemble their parents very much, but not wholly
-—each being possesses its individuality. This " variation "
itself varies in amount, but it is always present, not only in

vii CREATION BY LAW 143

the whole organism, but in every part of each organism.
Every organ, every character, every feeling, is individual;
that is to say, varies from the same organ, character, or feeling
in every other individual.

5. The Law of unceasing Change of Physical Conditions upon
the Surface of the Earth. — Geology shows us that this change
has always gone on in times past, and we also know that it
is now everywhere going on.

6. The Equilibrium or Harmony of Nature. — When a species
is well adapted to the conditions which environ it, it nourishes;
when imperfectly adapted it decays; when ill-adapted it
becomes extinct. If all the conditions which determine an
organism's wellbeing are taken into consideration, this state-
ment can hardly be disputed.

This series of facts or laws are mere statements of what
is the condition of nature. They are facts or inferences which
are generally known, generally admitted — but, in discussing
the subject of the "Origin of Species," as generally for-
gotten. It is from these universally admitted facts that the
origin of all the varied forms of nature may be deduced by
a logical chain of reasoning, which, however, is at every step
verified and shown to be in strict accord with facts ; and, at
the same time, many curious phenomena which can by no
other means be understood are explained and accounted for.
It is probable that these primary facts or laws are but results
of the very nature of life, and of the essential properties of
organised and unorganised matter. Mr. Herbert Spencer, in
his First Principles and his Biology, has, I think, made us able
to understand how this may be; but at present we may
accept these simple laws without going further back, and the
question then is — whether the variety, the harmony, the
contrivance, and the beauty we perceive in organic beings
can have been produced by the action of these laws alone, or
whether we are required to believe in the incessant interfer-
ence and direct action of the mind and will of the Creator.
It is simply a question of how the Creator has worked. The
Duke (and I quote him as having well expressed the views
of the more intelligent of Mr. Darwin's opponents) maintains
that He has personally applied general laws to produce effects

144 NATURAL SELECTION vn

which those laws are not in themselves capable of producing ;
that the universe alone, with all its laws intact, would be
a sort of chaos, without variety, without harmony, without
design, without beauty; that there is not (and therefore we
may presume that there could not be) any self -developing
power in the universe. I believe, on the contrary, that the
universe is so constituted as to be self-regulating ; that as
long as it contains Life, the forms under which that life is
manifested have an inherent power of adjustment to each
other and to surrounding nature ; and that this adjustment
necessarily leads to the greatest amount of variety and beauty
and enjoyment, because it does depend on general laws, and
not on a continual supervision and rearrangement of details.
As a matter of feeling and religion, I hold this to be a far
higher conception of the Creator and of the Universe than
that which may be called the "continual interference"
hypothesis ; but it is not a question to be decided by our
feelings or convictions — it is a question of facts and of reason.
Could the change which geology shows us has continually
taken place in the forms of life, have been produced by general
laws, or does it imperatively require the incessant supervision
of a creative mind ? This is the question for us to consider,
and our opponents have the difficult task of proving a nega-
tive, if we show that there are both facts and analogies in
our favour.1

Mr. Darwin's Metaphors liable to Misconception
Mr. Darwin has laid himself open to much misconception,
and has given to his opponents a powerful weapon against
himself, by his continual use of metaphor in describing the
wonderful co-adaptations of organic beings.

" It is curious," says the Duke of Argyll, " to observe the
language which this most advanced disciple of pure naturalism
instinctively uses, when he has to describe the complicated
structure of this curious order of plants (the Orchids).
' Caution in ascribing intentions to nature ' does not seem to

1 In addition to the laws referred to above, there are of course the funda-
mental laws and properties of organised matter and the mysterious powers of
Life, which we shall probably never be able to explain, but which must be
taken as the basis of all attempts to account for the details of form and
structure in organised beings.

CREATION BY LAW 145

occur to him as possible. Intention is the one thing which
he does see, and which, when he does not see, he seeks for
diligently until he finds it. He exhausts every form of words
and of illustration, by which intention or mental purpose can
be described. ' Contrivance' — 'curious contrivance,' — 'beauti-
ful contrivance,' — these are expressions which occur over and
over again. Here is one sentence describing the parts of a
particular species : ' The labellum is developed into a long
nectary, in order to attract Lepidoptera, and we shall presently
give reason for suspecting that the nectar is purposely so
lodged that it can be sucked only slowly in order to give time
for the curious chemical quality of the viscid matter setting
hard and dry.' " Many other examples of similar expressions
are quoted by the Duke, who maintains that no explanation
of these " contrivances " has been or can be given, except on
the supposition of a personal contriver, specially arranging
the details of each case, although causing them to be produced
by the ordinary processes of growth and reproduction.

Now there is a difficulty in this view of the origin of the
structure of Orchids which the Duke does not allude to. The
majority of flowering plants are fertilised, either without the
agency of insects or, when insects are required, without any
very important modification of the structure of the flower.
It is evident, therefore, that flowers might have been formed
as varied, fantastic, and beautiful as the orchids, and yet have
been fertilised without more complexity of structure than is
found in violets, or clover, or primroses, or a thousand other
flowers. The strange springs and traps and pitfalls found in
the flowers of orchids cannot be necessary per se, since exactly
the same end is gained in ten thousand other flowers which
do not possess them. Is it not then an extraordinary idea, to
imagine the Creator of the universe contriving the various
complicated parts of these flowers, as a mechanic might con-
trive an ingenious toy or a difficult puzzle ? Is it not a more
worthy conception that they are some of the results of those
general laws which were so co-ordinated at the first intro-
duction of life upon the earth as to result necessarily in the
utmost possible development of varied forms ?

But let us take one of the simpler cases adduced and see
if our general laws are unable to account for it.
L

14e NATURAL SELECTION vir

A Case of Orchid-structure explained by Natural Selection

There is a Madagascar orchid— the Angrsecum sesquipedale

with an immensely long and deep nectary. How did such

an extraordinary organ come to be developed ? Mr. Darwin's
explanation is this. The pollen of this flower can only be
removed by the base of the proboscis of some very large
moths, when trying to get at the nectar at the bottom of the
vessel. The moths with the longest probosces would do this
most effectually; they would be rewarded for their long
tongues by getting the most nectar ; whilst on the other hand,
the flowers with the deepest nectaries would be the best
fertilised by the largest moths preferring them. Conse-
quently, the deepest nectaried orchids and the longest tongued
moths would each confer on the other an advantage in the
battle of life. This would tend to their respective perpetua-
tion, and to the constant lengthening of nectaries and pro-
bosces. Now let it be remembered that what we have to
account for is only the unusual length of this organ. A nec-
tary is found in many orders of plants and is especially
common in the orchids, but in this one case only is it some-
times more than a foot long. How did this arise ? We begin
with the fact, proved experimentally by Mr. Darwin, that
moths do visit orchids, do thrust their spiral trunks into the
nectaries, and do fertilise them by carrying the pollinia of one
flower to the stigma of another. He has further explained
the exact mechanism by which this is effected, and the Duke
of Argyll admits the accuracy of his observations. In our
British species, such as Orchis pyramidalis, it is not necessary
that there should be any exact adjustment between the length
of the nectary and that of the proboscis of the insect ; and
thus a number of insects of various sizes are found to carry
away the pollinia and aid in the fertilisation. In the
Angraecum sesquipedale, however, it is necessary that the
proboscis should be forced into a particular part of the flower,
and this would only be done by a large moth burying its pro-
boscis to the very base, and straining to drain the nectar from
the bottom of the long tube, in which it occupies a depth of
one or two inches only. Now let us start from the time when
the nectary was only half its present length or about six

CREATION BY LAW 147

inches, and was chiefly fertilised by a species of moth which
appeared at the time of the plant's flowering, and whose pro-
boscis was of the same length. Among the millions of flowers
of the Angrsecum produced every year, some would always be
shorter than the average, some longer. The former, owing
to the structure of the flower, would not get fertilised, be-
cause the moths could get all the nectar without forcing their
trunks down to the very base. The latter would be well
fertilised, and the longest would on the average be the best
fertilised of all. By this process alone the average length
of the nectary would annually increase, because, the short-
nectaried flowers being sterile and the long ones having
abundant offspring, exactly the same effect would be produced
as if a gardener destroyed the short ones and sowed the seed
of the long ones only ; and this we know by experience
would produce a regular increase of length, since it is this
very process which has increased the size and changed the
form of our cultivated fruits and flowers.

But this would lead in time to such an increased length
of the nectary that many of the moths could only just reach
the surface of the nectar, and only the few with exceptionally
long trunks be able to suck up a considerable portion.

This would cause many moths to neglect these flowers
because they could not get a satisfying supply of nectar, and
if these were the only moths in the country the flowers would
undoubtedly suffer, and the further growth of the nectary be
checked by exactly the same process which had led to its
increase. But there are an immense variety of moths, of
various lengths of proboscis, and as the nectary became longer,
other and larger species would become the fertilisers, and
would carry on the process till the largest moths became the
sole agents. Now, if not before, the moth would also be
affected, for those with the longest probosces would get most
food, would be the strongest and most vigorous, would visit
and fertilise the greatest number of flowers, and would leave
the largest number of descendants. The flowers most com-
pletely fertilised by these moths being those which had the
longest nectaries, there would in each generation be on the
average an increase in the length of the nectaries, and also
an average increase in the length of the probosces of the

148 NATURAL SELECTION vn

moths ; and this would be a necessary result from the fact that
nature ever fluctuates about a mean, or that in every genera-
tion there would be flowers with longer and shorter nectaries,
and moths with longer and shorter probosces than the average.
No doubt there are a hundred causes that might have checked
this process before it had reached the point of development
at which we find it. If, for instance, the variation in the
quantity of nectar had been at any stage greater than the
variation in the length of the nectary, then smaller moths
could have reached it and have effected the fertilisation. Or
if the growth of the probosces of the moths had from other
causes increased quicker than that of the nectary, or if the
increased length of proboscis had been injurious to them in
any way, or if the species of moth with the longest proboscis
had become much diminished by some enemy or other un-
favourable conditions, then, in any of these cases, the shorter
nectaried flowers, which would have attracted and could have
been fertilised by the smaller kinds of moths, would have had
the advantage. And checks of a similar nature to these no
doubt have acted in other parts of the world, and have pre-
vented such an extraordinary development of nectary as has
been produced by favourable conditions in Madagascar only,
and in one single species of orchid. I may here mention that
some of the large Sphinx moths of the tropics have probosces
nearly as long as the nectary of Angrsecum sesquipedale. I
have carefully measured the proboscis of a specimen of Macro-
sila cluentius from South America, in the collection of the British
Museum, and find it to be nine inches and a quarter long !
One from tropical Africa (Macrosila morganii) is seven inches
and a half. A species having a proboscis two or three inches
longer could reach the nectar in the largest flowers of Angrae-
cum sesquipedale, whose nectaries vary in length from ten
to fourteen inches. That such a moth exists in Madagascar
may be safely predicted ; and naturalists who visit that island
should search for it with as much confidence as astronomers
searched for the planet Neptune, — and I venture to predict
they will be equally successful !

Now, instead of this beautiful self-acting adjustment, the
opposing theory is, that the Creator of the universe, by a
direct act of His will, so disposed the natural forces influencing

vii CREATION BY LAW 149

the growth of this one species of plant as to cause its nectary
to increase to this enormous length ; and at the same time,
by an equally special act, determined the flow of nourishment
in the organisation of the moth, so as to cause its proboscis to
increase in exactly the same proportion, having previously so
constructed the Angrsecum that it could only be maintained
in existence by the agency of this moth. But what proof is
given or suggested that this was the mode by which the ad-
justment took place ? None whatever, except a feeling that
there is an adjustment of a delicate kind, and an inability to
see how known causes could have produced such an adjust-
ment. I believe I have shown, however, that such an
adjustment is not only possible but inevitable, unless at some
point or other we deny the action of those simple laws which
we have already admitted to be but the expressions of exist-
ing facts.

Adaptation brought about by General Laws

It is difficult to find anything like parallel cases in inorganic
nature, but that of a river may perhaps illustrate the subject
in some degree. Let us suppose a person totally ignorant of
modern geology to study carefully a great river system. He
finds in its lower part a deep broad channel filled to the
brim, flowing slowly through a flat country and carrying out
to the sea a quantity of fine sediment. Higher up it branches
into a number of smaller channels, flowing alternately through
flat valleys and between high banks ; sometimes he finds a
deep rocky bed with perpendicular walls, carrying the water
through a chain of hills ; where the stream is narrow he finds
it deep, where wide shallow. Farther up still, he comes to a
mountainous region, with hundreds of streams and rivulets,
each with its tributary rills and gullies, collecting the water
from every square mile of surface, and every channel adapted
to the water that it has to carry. He finds that the bed of
every branch and stream and rivulet has a steeper and
steeper slope as it approaches its sources, and is thus enabled
to carry off the water from heavy rains, and to bear away
the stones and pebbles and gravel that would otherwise block
up its course. In every part of this system he would see
exact adaptation of means to an end. He would say that
this system of channels must have been designed, it answers

150 NATURAL SELECTION vn

its purpose so effectually. Nothing but a mind could have so
exactly adapted the slopes of the channels, their capacity, and
frequency, to the nature of the soil and the quantity of the
rainfall. Again, he would see special adaptation to the wants
of man, in broad, quiet, navigable rivers flowing through fertile
plains that support a large population, while the rocky streams
and mountain torrents were confined to those sterile regions
suitable only for a small population of shepherds and herds-
men. He would listen with incredulity to the geologist who
assured him that the adaptation and adjustment he so admired
was an inevitable result of the action of general laws ; that
the rains and rivers, aided by subterranean forces, had
modelled the country, had formed the hills and valleys, had
scooped out the river beds and levelled the plains ; and it
would only be after much patient observation and study,
after having watched the minute changes produced year by
year, and multiplying them by thousands and ten thousands,
— after visiting the various regions of the earth and seeing the
changes everywhere going on, and the unmistakable signs of
greater changes in past times, — that he could be made to
understand that the surface of the earth, however beautiful
and harmonious it may appear, is strictly due in every detail
to the action of forces which are demonstrably self-adjusting.
Moreover, when he had sufficiently extended his inquiries,
he would find that every evil effect which he would imagine
must be the result of non-adjustment does somewhere or other
occur, only it is not always evil. Looking on a fertile valley,
he would perhaps say : " If the channel of this river were not
well adjusted — if for a few miles it sloped the wrong way —
the water could not escape, and all this luxuriant valley, full of
human beings, would become a waste of waters." Well, there
are hundreds of such cases. Every lake is a valley "wasted
by water," and in some cases (as the Dead Sea) it is a positive
evil, a blot upon the harmony and adaptation of the surface
of the earth. Again, he might say — "If rain did not fall
here, but the clouds passed over us to some other regions,
this verdant and highly cultivated plain would become a
desert." And there are such deserts over large portions of
the earth, which abundant rains would convert into pleasant
dwelling-places for man. Or he might observe some great

vii CREATION BY LAW 161

navigable river, and reflect how easily rocks, or a steeper
channel in places, might render it useless to man ; — and a
little inquiry would show him hundreds of rivers in every
part of the world, which are thus rendered useless for
navigation.

Exactly the same thing occurs in organic nature. We see
some one wonderful case of adjustment, some unusual develop-
ment of an organ, but we pass over the hundreds of cases in
which that adjustment and development do not occur. No
doubt when one adjustment is absent another takes its place,
because no organism can continue to exist that is not adjusted
to its environment ; and unceasing variation, with unlimited
powers of multiplication, in most cases, furnishes the means
of self-adjustment. The world is so constituted that by the
action of general laws there is produced the greatest possible
variety of surface and of climate ; and by the action of laws
equally general, the greatest possible variety of organisms has
been produced, adapted to the varied conditions of every part of
the earth. The objector would probably himself admit that
the varied surface of the earth — the plains and valleys, the
hills and mountains, the deserts and volcanoes, the winds and
currents, the seas and lakes and rivers, and the various
climates of the earth — are all the results of general laws
acting and reacting during countless ages ; and that the
Creator does not appear to guide and control the action of
these laws — here determining the height of a mountain, there
altering the channel of a river — here making the rains more
abundant, there changing the direction of a current. He
would probably admit that the forces of inorganic nature are
self-adjusting, and that the result necessarily fluctuates about
a given mean condition (which is itself slowly changing), while
within certain limits the greatest possible amount of variety
is produced. If then a " contriving mind " is not necessary
at every step of the process of change eternally going on in
the inorganic world, why are we required to believe in the con-
tinual action of such a mind in the region of organic nature ?
True, the laws at work are more complex, the adjustments
more delicate, the appearance of special adaptation more
remarkable ; but why should we measure the creative mind
by our own? Why should we suppose the machine too

152 NATURAL SELECTION vii

' — >*

complicated to have been designed by the Creator so com-
plete that it would necessarily work out harmonious results ?
The theory of " continual interference " is a limitation of the
Creator's power. It assumes that He could not work by pure
law in the organic, as He has done in the inorganic world ; it
assumes that He could not foresee the consequences of the laws
of matter and mind combined — that results would continually
arise which are contrary to what is best — and that He has to
change what would otherwise be the course of nature in order
to produce that beauty, and variety, and harmony which even
we, with our limited intellects, can conceive to be the result
of self-adjustment in a universe governed by unvarying law.
If we could not conceive the world of nature to be self-adjust-
ing and capable of endless development, it would even then
be an unworthy idea of a Creator to impute the incapacity of
our minds to Him; but when many human minds can conceive,
and can even trace out in detail, some of the adaptations in
nature as the necessary results of unvarying law, it seems
strange that, in the interests of religion, any one should seek
to prove that the System of Nature, instead of being above,
is far below our highest conceptions of it. I, for one, cannot
believe that the world would come to chaos if left to law
alone. I cannot believe that there is in it no inherent power
of developing beauty or variety, and that the direct action of
the Deity is required to produce each spot or streak on every
insect, each detail of structure in every one of the millions of
organisms that live or have lived upon the earth. For it is
impossible to draw a line. If any modifications of structure
could be the result of law, why not all ? If some self -adapta-
tions could arise, why not others 1 If any varieties of colour,
why not all the varieties we see ? No attempt is made to
explain this, except by reference to the fact that " purpose "
and " contrivance " are everywhere visible, and by the illo-
gical deduction that they could only have arisen from the
direct action of some mind, because the direct action of our
minds produces similar " contrivances " ; but it is forgotten
that adaptation, however produced, must have the appearance
of design. The channel of a river looks as if made far the
river, although it is made by it ; the fine layers and beds in a
deposit of sand often look as if they had been sorted, and

vii CREATION BY LAW 153

sifted, and levelled designedly; the sides and angles of a
crystal exactly resemble similar forms designed by man ; but
we do not therefore conclude that these' effects have, in each
individual case, required the directing action of a creative
mind, or see any difficulty in their being produced by natural
law.

in Nature

Let us, however, leave this general argument for a while,
and turn to another special case, which has been appealed to
as conclusive against Mr. Darwin's views. " Beauty " is, to
some persons, as great a stumbling-block as ".contrivance."
They cannot conceive a system of the universe so perfect as
necessarily to develop every form of beauty, but suppose that
when anything specially beautiful occurs, it is a step beyond
what that system could have produced — something which the
Creator has added for his own delectation.

Speaking of the humming birds, the Duke of Argyll says :
" In the first place it is to be observed of the whole group,
that there is no connection which can be traced or conceived,
between the splendour of the humming birds and any function
essential to their life. If there were any such connection,
that splendour could not be confined, as it almost exclusively
is, to only one sex. The female birds are, of course, not
placed at any disadvantage in the struggle for existence by
their more sombre colouring." And after describing the
various ornaments of these birds, he says : " Mere ornament
and variety of form, and these for their own sake, is the only
principle or rule with reference to which Creative Power
seems to have worked in these wonderful and beautiful birds.
... A crest of topaz is no better in the struggle for existence
than a crest of sapphire. A frill ending in spangles of
the emerald is no better in the battle of life than a frill ending
in spangles of the ruby. A tail is not affected for the pur-
poses of flight, whether its marginal or its central feathers are
decorated with white. . . . Mere beauty and mere variety,
for their own sake, are objects which we ourselves seek when
we can make the forces of nature subordinate to the attain-
ment of them. There seems to be no conceivable reason why
we should doubt or question that these are ends and aims

154 NATURAL SELECTION vn
>»

also in the forms given to living organisms " (Reign of Law,
p. 248).

Here the statement that " no connection can be conceived
between the splendour of the humming birds and any function
essential to their life," is met by the fact that Mr. Darwin
has not only conceived but has shown, both by observation
and reasoning, how beauty of colour and form may have a
direct influence on the most important of all the functions of
life, that of reproduction. In the variations to which birds
are subject, any more brilliant colour than usual is believed
to be attractive to the females, and would therefore lead to
the individuals so adorned leaving more than the average
number of offspring. There are some indications that this kind
of sexual selection does actually take place, and the laws of
inheritance would necessarily lead to the further development
of any individual peculiarity that was attractive, and thus the
splendour of the humming birds is directly connected with
their very existence. It is true that "a crest of topaz may
be no better than a crest of sapphire," but either of these may
be much better than no crest at all ; and the different condi-
tions under which the parent form must have existed in
different parts of its range will have determined different
variations of tint, either of which were advantageous.1 The
reason why female birds are not adorned with equally brilliant
plumes is sufficiently clear ; they would be injurious by ren-
dering their possessors too conspicuous during incubation.
Survival of the fittest has therefore favoured the development
of those dark green tints on the upper surface of so many
female humming birds, which are most conducive to their
protection while the important functions of hatching and
rearing the young are being carried on. Keeping in mind
the laws of multiplication, variation, and survival of the
fittest, which are for ever in action, these varied develop-

1 Since writing this essay I have come to the conclusion that mere
diversity of colouring between species is an important factor in their differ-
entiation, serving as a means of recognition, and thus preventing cross-
unions. See Damnnism, p. 217. I have also been led to doubt the reality
of the fact of female selection of slight differences of colour on which Mr.
Darwin relied, but it has not been thought advisable to alter the passages
which seem to admit it, as they represent my belief at the time they were

CREATION BY LAW 155

ments of beauty and harmonious adjustments to conditions
are not only conceivable but demonstrable results.

The objection I am now combating is solely founded on
the supposed analogy of the Creator's mind to ours as regards
the love of beauty for its own sake ; but if this analogy is to
be trusted, then there ought to be no natural objects which
are disagreeable or ungraceful in our eyes. And yet it is
undoubtedly the fact that there are many such. Just as
surely as the horse and deer are beautiful and graceful, the
elephant, rhinoceros, hippopotamus, and camel are the reverse.
The majority of monkeys and apes are not beautiful ; the
majority of birds have no beauty of colour ; a vast number of
insects and reptiles are positively ugly. Now, if the Creator's
mind is like ours, whence this ugliness ? It is useless to say
" that is a mystery we cannot explain," because we have
attempted to explain one -half of creation by a method that
will not apply to the other half. We know that a man with
the highest taste and with unlimited wealth practically does
abolish all ungraceful and disagreeable forms and colours from
his own domains. If the beauty of creation is to be explained
by the Creator's love of beauty, we are bound to ask why He
has not banished deformity from the earth, as the wealthy and
enlightened man does from his estate and from his dwelling ;
and if we can get no satisfactory answer, we shall do well to
reject the explanation offered. Again, in the case of flowers,
which are always especially referred to as the surest evidence
of beauty being an end of itself in creation, the whole of the
facts are never fairly met. At least half the plants in the
world have not bright-coloured or beautiful flowers ; and Mr.
Darwin has lately arrived at the wonderful generalisation
that flowers have become beautiful solely to attract insects to
assist in their fertilisation. He adds, " I have come to this
conclusion from finding it an invariable rule, that when a
flower is fertilised by the wind it never has a gaily-coloured
corolla." Here is a most wonderful case of beauty being
useful, when it might be least expected. But much more is
proved ; for when beauty is of no use to the plant it is not
given. It cannot be imagined to do any harm. It is simply
not necessary, and is therefore withheld ! We ought surely
to have been told how this fact is consistent with beauty

166 NATURAL SELECTION vn

„ - — •*

being " an end in itself," and with the statement of its being
given to natural objects " for its own sake."

How New Forms are, produced by Variation and Selection
Let us now consider another of the popular objections
which the Duke of Argyll thus sets forth : —

"Mr. Darwin does not pretend to have discovered any
law or rule, according to which new forms have been born
from old forms. He does not hold that outward conditions,
however changed, are sufficient to account for them. . . . His
theory seems to be far better than a mere theory — to be an
established scientific truth — in so far as it accounts, in part at
least, for the. success and establishment and spread of new
forms when they have arisen. But it does not even suggest the
law under which, or by or according to which, such new forms
are introduced. Natural Selection can do nothing, except
with the materials presented to its hands. It cannot select
except among the things open to selection. . . . Strictly
speaking, therefore, Mr. Darwin's theory is not a theory on
the Origin of Species at all, but only a theory on the causes
which lead to the relative success or failure of such new forms
as may be born into the world " (Reign of Law, p. 230).

In this and many other passages in his work the Duke
of Argyll sets forth his idea of creation as a "creation by
birth," but maintains that each birth of a new form from
parents differing from itself has been produced by a special
interference of the Creator, in order to direct the process of
development into certain channels ; that each new species is
in fact a " special creation," although brought into existence
through the ordinary laws of reproduction. He maintains,
therefore, that the laws of multiplication and variation cannot
furnish the right kinds of materials at the right times for
natural selection to work on. I believe, on the contrary,
that it can be logically proved from the six axiomatic laws
before laid down, that such materials would be furnished ; but
I prefer to show there are abundance of facts which demon-
strate that they are furnished.

The experience of all cultivators of plants and breeders of
animals shows that, when a sufficient number of individuals
are examined, variations of any required kind can always be

CREATION BY LAW 157

met with. On this depends the possibility of obtaining
breeds, races, and fixed varieties of animals and plants • and it
is found that any one form of variation may be accumulated
by selection, without materially affecting the other characters
of the species ; each seems to vary in the one required direction
only. For example, in turnips, radishes, potatoes, and carrots
the root or tuber varies in size, colour, form, and flavour, while
the foliage and flowers seem to remain almost stationary ; in
the cabbage and lettuce, on the contrary, the foliage can be
modified into various forms and modes of growth, the root,
flower, and fruit remaining little altered ; in the cauliflower
and broccoli the flower heads vary ; in the garden pea the pod
only changes. We get innumerable forms of fruit in the
apple and pear, while the leaves and flowers remain almost
undistinguishable ; the same occurs in the gooseberry and
garden currant. Directly, however (in the very same genus),
we want the flower to vary in the Kibes sanguineum, it does
so, although mere cultivation for hundreds of years has not
produced marked differences in the flowers of Eibes grossu-
laria. When fashion demands any particular change in the
form, or size, or colour of a flower, sufficient variation always
occurs in the right direction, as is shown by our roses, auri-
culas, and geraniums ; when, as recently, ornamental leaves
come into fashion, sufficient variation is found to meet the
demand, and we have zoned pelargoniums and variegated
ivy, and it is discovered that a host of our commonest shrubs
and herbaceous plants have taken to vary in this direction
just when we want them to do so ! This rapid variation is
not confined to old and well-known plants subjected for a long
series of generations to cultivation, but the Sikkim rhodo-
dendrons, the fuchsias, and calceolarias from the Andes, and
the pelargoniums from the Cape, are equally accommodating,
and vary just when and where and how we require them.

Turning to animals we find equally striking examples.
If we want any special quality in any animal we have only to
breed it in sufficient quantities and watch carefully, and the
required variety is always found, and can be increased to
almost any desired extent. In sheep, we get flesh, fat, and
wool ; in cows, milk ; in horses, colour, strength, size, and
speed ; in poultry, we have got almost any variety of colour,

158 NATURAL SELECTION vn

curious modifications of plumage, and the capacity of per-
petual egg-laying. In pigeons we have a still more remark-
able proof of the universality of variation, for it has been at
one time or another the fancy of breeders to change the form
of every part of these birds, and they have never found the
required variations absent. The form, size, and shape of bill
and feet have been changed to such a degree as is found only
in distinct genera of wild birds ; the number of tail feathers
has been increased, a character which is generally one of the
most permanent nature, and is of high importance in the
classification of birds ; and the size, the colour, and the habits
have been also changed to a marvellous extent. In dogs,
the degree of modification and the facility with which it is
effected is almost equally apparent. Look at the constant
amount of variation in opposite directions that must have
been going on to develop the poodle and the greyhound from
the same original stock ! Instincts, habits, intelligence, size,
speed, form, and colour have always varied, so as to produce
the very races which the wants or fancies or passions of
men may have led them to desire. Whether they wanted a
bull-dog to torture another animal, a greyhound to catch a
hare, or a bloodhound to hunt down their oppressed fellow-
creatures, the required variations have always appeared.

Now this great mass of facts, of which a mere sketch has
been here given, are fully accounted for by the "Law of
Variation " as laid down at the commencement of this paper.
Universal variability — small in amount, but in every direction,
ever fluctuating about a mean condition until made to advance
in a given direction by " selection," natural or artificial — is
the simple basis for the indefinite modification of the forms
of life ; partial, unbalanced, and consequently unstable modi-
fications being produced by man, while those developed under
the unrestrained action of natural laws are at every step self-
adjusted to external conditions by the dying out of all
unadjusted forms, and are therefore stable and comparatively
permanent.1 To be consistent in their views, our opponents
must maintain that every one of the variations that have
rendered possible the changes produced by man have been

1 That the variations occiirring among wild animals are ample both in num-
ber and amount is proved in Darvrinism, chap. iii.

CREATION BY LAW 159

determined at the right time and place by the will of the
Creator. Every race produced by the florist or the breeder,
the dog or the pigeon fancier, the ratcatcher, the sporting man,
or the slave-hunter, must have been provided for by varieties
occurring when wanted ; and as these variations were never
withheld, it would prove that the sanction of an all -wise
and all-powerful Being has been given to that which the
highest human minds consider to be trivial, mean, or debasing.
This appears to be a complete answer to the theory that
variation sufficient in amount to be accumulated in a given
direction must be the direct act of the creative mind, but it is
also sufficiently condemned by being so entirely unnecessary.
The facility with which man obtains new races depends chiefly
upon the number of individuals he can procure to select from.
When hundreds of florists or breeders are all aiming at the
same object, the work of change goes on rapidly. But a
common species in nature contains a thousand or a million-
fold more individuals than any domestic race ; and survival
of the fittest must unerringly preserve all that vary in the
right direction, not only in obvious characters but in minute
details — not only in external but in internal organs ; so that if
the materials are sufficient for the needs of man, there can be
no want of them to fulfil the grand purpose of keeping up a
supply of modified organisms, exactly adapted to the changed
conditions that are always occurring in the inorganic world.

Tfte Objection that there are Limits to Variation
Having now, I believe, fairly answered the chief objections
of the Duke of Argyll, I proceed to notice one or two of those
adduced in an able and argumentative essay on the " Origin
of Species" in the North British Review for July 1867. The
writer first attempts to prove that there are strict limits to
variation. When we begin to select variations in any one
direction, the process is comparatively rapid, but after a con-
siderable amount of change has been effected it becomes
slower and slower, till at length its limits are reached and no
care in breeding and selection can produce any further advance.
The racehorse is chosen as an example. It is admitted that,
with any ordinary lot of horses to begin with, careful selection
would in a few years make a great improvement, and in a

NATURAL SELECTION

comparatively short time the standard of our best racers might
be reached. But that standard has not for many years been
materially raised, although unlimited wealth and energy are
expended in the attempt. This is held to prove that there
are definite limits to variation in any special direction, and
that we have no reason to suppose that mere time, and the
selective process being carried on by natural law, could make
any material difference. But the writer does not perceive
that this argument fails to meet the real question, which is,
not whether indefinite and unlimited change in any or all
directions is possible, but whether such differences as do occur
in nature could have been produced by the accumulation of
variations by selection. In the matter of speed, a limit of a
definite kind as regards land animals does exist in nature.
All the swiftest animals — deer, antelopes, hares, foxes, lions,
leopards, horses, zebras, and many others — have reached very
nearly the same degree of speed. Although the swiftest of
each must have been for ages preserved, and the slowest must
have perished, we have no reason to believe there is any
advance of speed. The possible limit under existing con-
ditions, and perhaps under possible terrestrial conditions, has
been long ago reached. In cases, however, where this limit had
not been so nearly reached as in the horse, we have been
enabled to make a more marked advance and to produce a
greater difference of form. The wild dog is an animal that
hunts much in company, and trusts more to endurance than
to speed. Man has produced the greyhound, which differs
much more from the wolf or the dingo than the racer does
from the wild Arabian. Domestic dogs, again, have varied
more in size and in form than the whole family of Canidse in
a state of nature. No wild dog, fox, or wolf is either so
small as some of the smallest terriers and spaniels, or so large
as the largest varieties of hound or Newfoundland dog. And,
certainly, no two wild animals of the family differ so widely
in form and proportions as the Chinese pug and the Italian
greyhound, or the bulldog and the common greyhound. The
known range of variation is, therefore, more than enough for
the derivation of all the forms of dogs, wolves, and foxes
from a common ancestor.

Again, it is objected that the pouter or the fan-tail pigeon

vii CREATION BY LAW 161

cannot be further developed in the same direction. Variation
seems to have reached its limits in these birds. But so it has
in nature. The fantail has not only more tail feathers than
any of the three hundred and sixty existing species of pigeons,
but more than any of the ten thousand known species of birds.
There is, of course, some limit to the number of feathers of
which a tail useful for flight can consist, and in the fantail we
have probably reached that limit. Many birds have the
oesophagus or the skin of the neck more or less dilatable, but
in no known bird is it so dilatable as in the pouter pigeon.
Here again the possible limit, compatible with a healthy
existence, has probably been reached. In like manner tho
differences in the size and form of the beak in the various
breeds of the domestic pigeon is greater than that between
the extreme forms of beak in the various genera and sub-
families of the whole pigeon tribe. From these facts, and many
others of the same nature, we may fairly infer that if rigid
selection were applied to any organ, we could in a comparatively
short time produce a much greater amount of change than
that which occurs between species and species in a state of
nature, since the differences which we do produce are often
comparable with those which exist between distinct genera or
distinct families. The facts adduced by the writer of the
article referred to, of the definite limits to variability in certain
directions in domesticated animals, are, therefore, no objection
whatever to the view that all the modifications which exist in
nature have been produced by the accumulation, by natural
selection, of small and useful variations, since those very
modifications have equally definite and very similar limits.

Objection to the Argument from Classification
To another of this writer's objections — that by Professor
Thomson's calculations the sun can only have existed in a
solid state 500,000,000 of years, and that therefore time
would not suffice for the slow process of development of all
living organisms — it is hardly necessary to reply, as it cannot
be seriously contended, even if this calculation has claims to
approximate accuracy, that the process of change and develop-
ment may not have been sufficiently rapid to have occurred
within that period. His objection to the classification argu-

51

162 NATURAL SELECTION vn

ment is, however, more plausible. The uncertainty of opinion
among naturalists as to which are species and which varieties,
is one of Mr. Darwin's very strong arguments that these two
names cannot belong to things quite distinct in nature and
origin. The reviewer says that this argument is of no weight,
because the works of man present exactly the same phenomena ;
and he instances patent inventions, and the excessive difficulty
of determining whether they are new or old. I accept the
analogy, though it is a very imperfect one, and maintain that,
such as it is, it is all in favour of Mr. Darwin's views. For
are not all inventions of the same kind directly affiliated to a
common ancestor ? Are not improved steam-engines or clocks
the lineal descendants of some existing steam-engine or clock 1
Is there ever a new creation in art or science any more than
in nature 1 Did ever patentee absolutely originate any
complete and entire invention, no portion of which was
derived from anything that had been made or described
before 1 It is therefore clear that the difficulty of distin-
guishing the various classes of inventions which claim to be
new, is of the same nature as the difficulty of distinguish-
ing varieties and species, because neither are absolutely new
creations, but both are alike descendants of pre-existing forms,
from which and from each other they differ by varying and
often imperceptible degrees. It appears, then, that however
plausible this writer's objections may seem, whenever he
descends from generalities to any specific statement, his
supposed difficulties turn out to be in reality strongly con-
firmatory of Mr. Darwin's view.

The TIMES on Natural Selection

The extraordinary misconception of the whole subject by
popular writers and reviewers is well shown by an article
which appeared in the Times newspaper on "The Reign of
Law." Alluding to the supposed economy of nature, in the
adaptation of each species to its own place and its special use,
the reviewer remarks : " To this universal law of the greatest
economy, the law of natural selection stands in direct
antagonism as the law of « greatest possible waste ' of time
and of creative power. To conceive a duck with webbed feet
and a spoon-shaped bill, living by suction, to pass naturally

CREATION BY LAW 163

into a gull with webbed feet and a knife-like bill, living on
flesh, in the longest possible time and in the most laborious
possible way, we may conceive it to pass from the one to the
other state by natural selection. The battle of life the ducks
will have to fight will increase in peril continually as they
cease (with the change of their bill) to be ducks, and attain a
maximum of danger in the condition in which they begin to
be gulls ; and ages must elapse and whole generations must
perish, and countless generations of the one species be created
and sacrificed, to arrive at one single pair of the other."

In this passage the theory of natural selection is so absurdly
misrepresented that it would be amusing, did we not consider
the misleading effect likely to be produced by this kind of
teaching in so popular a journal. It is assumed that the duck
and the gull are essential parts of nature, each well fitted for its
place, and that if one had been produced from the other by
a gradual metamorphosis, the intermediate forms would have
been useless, unmeaning, and unfitted for any place in the
system of the universe. Now, this idea can only exist in a
mind ignorant of the very foundation and essence of the
theory of natural selection, which is, the preservation of useful
variations only, or, as has been well expressed, in other words,
the " survival of the fittest." Every intermediate form which
could possibly have arisen during the transition from the duck
to the gull, so far from having an unusually severe battle to
fight for existence, or incurring any "maximum of danger,"
would necessarily have been as accurately adjusted to the rest
of nature, and as well fitted to maintain and to enjoy its
existence, as the duck or the gull actually are. If it were not
so, it never could have been produced under the law of natural
selection.

Intermediate or generalised Forms of extinct Animals, an

indication of Transmutation or Development
The misconception of this writer illustrates another point
yery frequently overlooked. It is an essential part of Mr.
Darwin's theory that one existing animal has not been
derived from any other existing animal, but that both are the
descendants of a common ancestor, which was at once different
from either, but, in essential characters, to some extent inter-

164 NATURAL SELECTION vn

mediate between them both. The illustration of the duck
and the gull is therefore misleading ; one of these birds has
not been derived from the other, but both from a common
ancestor. This is not a mere supposition invented to support
the theory of natural selection, but is founded on a variety of
indisputable facts. As we go back into past time, and meet
with the fossil remains of more and more ancient races of
extinct animals, we find that many of them actually are
intermediate between distinct groups of existing animals.
Professor Owen continually dwells on this fact : he says in
his Palceontology, p. 284 : "A more generalised vertebrate
structure is illustrated, in the extinct reptiles, by the affinities
to ganoid fishes, shown by Ganocephala, Labyrinthodontia, and
Ichthyopterygia ; by the affinities of the Pterosauria to birds,
and by the approximation of the Dinosauria to mammals.
(These have been recently shown by Professor Huxley to
have more affinity to birds.) It is manifested by the combina-
tion of modern crocodilian, chelonian, and lacertian characters
in the Cryptodontia and the Dicynodontia, and by the com-
bined lacertian and crocodilian characters in the Thecodontia
and Sauropterygia." In the same work he tells us that " the
Anoplotherium, in several important characters, resembled
the embryo Ruminant, but retained throughout life those
marks of adhesion to a generalised mammalian type ; " and
assures us that he has " never omitted a proper opportunity
for impressing the results of observations showing the more
generalised structures of extinct as compared with the more
specialised forms of recent animals." Modern palaeontologists
have discovered hundreds of examples of these more generalised
or ancestral types. In the time of Cuvier, the Kuminants
and the Pachyderms were looked upon as two of the most
distinct orders of animals ; but it is now demonstrated that
there once existed a variety of genera and species, connecting
by almost imperceptible grades such widely different animals
as the pig and the camel. Among living quadrupeds we can
scarcely find a more isolated group than the genus Equus,
comprising the horses, asses, and zebras ; but through many
species of Paloplotherium, Hippotherium, and Hipparion, and
numbers of extinct forms of Equus found in Europe, India,
and America, an almost complete transition is established with

CREATION BY LAW 165

the Eocene Anoplotherium and Paleotherium, which are also
generalised or ancestral types of the tapir and rhinoceros.
The recent researches of M. Gaudry in Greece have furnished
much new evidence of the same character. In the Miocene
(or Pliocene) beds of Pikermi he has discovered the group of
the Simocyonidse intermediate between bears and wolves ; the
genus Hysenictis which connects the hyaenas with the civets ;
the Ancylotherium, which is allied both to the extinct mas-
todon and to the living pangolin or scaly ant-eater ; and
the Helladotherium, which connects the now isolated giraffe
with the deer and antelops.

Between reptiles and fishes an intermediate type has been
found in the Archegosaurus of the Coal formation ; while the
Labyrinthodon of the Trias combined characters of the
Batrachia with those of crocodiles, lizards, and ganoid fishes.
Even birds, the most apparently isolated of all living forms,
and the most rarely preserved in a fossil state, have been
shown to possess undoubted affinities with reptiles ; and in
the Oolitic Archseopteryx, with its lengthened tail, feathered
on each side, we have one of the connecting links from the
side of birds ; while Professor Huxley has recently shown
that the entire order of Dinosaurians have remarkable affinities
to birds, and that one of them, the Compsognathus, makes a
nearer approach to bird organisation than does Archaeopteryx
to that of reptiles.

Analogous facts to these occur in other classes of animals,
as an example of which we have the authority of a distin-
guished paleontologist, M. Barande, quoted by Mr. Darwin, for
the statement that although the Palaeozoic Invertebrata can
certainly be classed under existing groups, yet at this ancient
period the groups were not so distinctly separated from each
other as they are now; while Mr. Scudder tells us that
some of the fossil insects discovered in the Coal formation
of America offer characters intermediate between those of
existing orders. Agassiz, again, insists strongly that the
more ancient animals resemble the embryonic forms of
existing species ; but as the embryos of distinct groups are
known to resemble each other more than the adult animals
(and in fact to be undistinguishable at a very early age), this
is the same as saying that the ancient animals are exactly

166

NATURAL SELECTION

what, on Darwin's theory, the ancestors of existing animals
ought to be ; and this, it must be remembered, is the evidence
of one of the strongest opponents of the theory of natural
selection.

Conclusion

I have thus endeavoured to meet fairly, and to answer
plainly, a few of the most common objections to the theory of
natural selection, and I have done so in every case by refer-
ring to admitted facts and to logical deductions from those
facts.

As an indication and general summary of the line of
argument I have adopted, I here give a brief demonstration
in a tabular form of the Origin of Species by means of Natural
Selection, referring for the facts to Mr. Darwin's works, and
to the pages in this volume, where they are more or less fully
treated.

A Demonstration of the Origin of Species by Natural Selection

PROVED FACTS

TOTAL NUMBER OF INDIVIDUALS
STATIONARY, p. 23.

STRUGGLE FOR EXISTENCE.

HEREDITY WITH VARIATION, or
general likeness with individual
differences of parents and off-
springs, pp. 142, 156, 179 (Origin
of Species, chaps, i. ii. v.)

SURVIVAL OF THE FITTEST.

CHANGE OF EXTERNAL CONDITIONS,
universal and unceasing. — See
Lyell's Principles of Geology.

NECESSARY CONSEQUENCES
(afterwards taken as Proved Facts)

the

deaths equalling the births on
the average, p. 24 (Origin of
Species, chap. iii. )

SURVIVAL OF THE FITTEST, or
Natural Selection ; meaning,
simply, that on the whole those
die who are least fitted to main-
tain their existence (Origin of
Species, chap, iv.)

CHANGES OF ORGANIC FORMS, to
keep them in harmony with the
Changed Conditions ; and as the
changes of conditions are perman-
ent changes, in the sense of not
reverting back to identical pre-
vious conditions, the changes of
organic forms must be in the
same sense permanent, and thus

. originate SPECIES.

VIII

THE DEVELOPMENT OF HUMAN RACES UNDER THE LAW OF

NATURAL SELECTION

AMONG the most advanced students of man there exists a
wide difference of opinion on some of the most vital questions
respecting his nature and origin. Anthropologists are now,
indeed, pretty well agreed that man is not a recent introduc-
tion into the earth. All who have studied the question now
admit that his antiquity is very great ; and that, though
we have to some extent ascertained the minimum of time
during which he must have existed, we have made no approxi-
mation towards determining that far greater period during which
he may have, and probably has existed. We can with toler-
able certainty affirm that man must have inhabited the earth a
thousand centuries ago, but we cannot assert that he positively
did not exist, or that there is any good evidence against his
having existed, for a period of ten thousand centuries. We
know positively that he was contemporaneous with many now
extinct animals, and has survived changes of the earth's
surface fifty or a hundred times greater than any that have
occurred during the historical period; but we cannot place
any definite limit to the number of species he may have
outlived, or to the amount of terrestrial change he may
have witnessed.

Wide differences of opinion as to Man's Origin
But while on this question of man's antiquity there is a
very general agreement, — and all are waiting eagerly for

1 First published in the Anthropological Revieio, May 1864 ; reprinted in
Contributions, etc., with some alterations and additions.

168 NATURAL SELECTION ^ vnr

fresh evidence to clear up those points which all admit to be
full of doubt, — on other and not less obscure and difficult
questions a considerable amount of dogmatism is exhibited ;
doctrines are put forward as established truths, no doubt or
hesitation is admitted, and it seems to be supposed that no
further evidence is required, or that any new facts can
modify our convictions. This is especially the case when we
inquire, — Are the various forms under which man now
exists primitive, or derived from pre-existing forms ; in
other words, is man of one or many species ? To this ques-
tion we immediately obtain distinct answers diametrically
opposed to each other : the one party positively maintaining
that man is a species and is essentially one — that all differences
are but local and temporary variations, produced by the
different physical and moral conditions by which he is
surrounded ; the other party maintaining with equal con-
fidence that man is a genus of many species, each of which
is practically unchangeable, and has ever been as distinct, or
even more distinct, than we now behold them. This differ-
ence of opinion is somewhat remarkable, when we consider
that both parties are well acquainted with the subject ; both
use the same vast accumulation of facts ; both reject those
early traditions of mankind which profess to give an account
of his origin ; and both declare that they are seeking fear-
lessly after truth alone ; yet each will persist in looking only
at the portion of truth on his own side of the question, and at
the error which is mingled with his opponent's doctrine. It
is my wish to show how the two opposing views can be com-
bined, so as to eliminate the error and retain the truth in
each, and it is by means of Mr. Darwin's celebrated theory
of Natural Selection that I hope to do this, and thus to har-
monise the conflicting theories of modern anthropologists.

Let us first see what each party has to say for itself. In
favour of the unity of mankind it is argued that there are
no races without transitions to others ; that every race
exhibits within itself variations of colour, of hair, of feature,
and of form, to such a degree as to bridge over, to a large
extent, the gap that separates it from other races. It is
asserted that no race is homogeneous ; that there is a tend-
ency to vary; that climate, food, and habits produce, and

vni THE DEVELOPMENT OF HUMAN RACES 169

render permanent, physical peculiarities, which, though slight
in the limited periods allowed to our observation, would, in
the long ages during which the human race has existed, have
sufficed to produce all the differences that now appear. It is
further asserted that the advocates of the opposite theory do
not agree among themselves ; that some would make three,
some five, some fifty or a hundred and fifty species of man ;
some would have had each species created in pairs, while
others require nations to have at once sprung into existence,
and that there is no stability or consistency in any doctrine
but that of one primitive stock.

The advocates of the original diversity of man, on the
other hand, have much to say for themselves. They argue
that proofs of change in man have never been brought for-
ward except to the most trifling amount, while evidence of
his permanence meets us everywhere. The Portuguese and
Spaniards, settled for two or three centuries in South
America, retain their chief physical, mental, and moral
characteristics ; the Dutch boers at the Cape, and the de-
scendants of the early Dutch settlers in the Moluccas, have
not lost the features or the colour of the Germanic races ;
the Jews, scattered over the world in the most diverse
climates, retain the same characteristic lineaments every-
where ; the Egyptian sculptures and paintings show us that,
for at least 4000 or 5000 years, the strongly contrasted
features of the Negro and the Semitic races have remained
altogether unchanged; while more recent discoveries prove
that the mound-builders of the Mississippi valley, and the
dwellers on Brazilian mountains, had, even in the very infancy
of the human race, some traces of the same peculiar and
characteristic type of cranial formation that now distinguishes
them.

If we endeavour to decide impartially on the merits of
this difficult controversy, judging solely by the evidence that
each party has brought forward, it certainly seems that the
best of the argument is on the side of those who maintain
the primitive diversity of man. Their opponents have not
been able to refute the permanence of existing races as far
back as we can trace them, and have failed to show, in a
single case, that at any former epoch the well marked varie-

170 NATURAL SELECTION ^ vin

ties of" mankind approximated more closely than they do at
the present day. At the same time this is but negative
evidence. A condition of immobility for four or five thou-
sand years does not preclude an advance at an earlier epoch,
and — if we can show that there are causes in nature which
would check any further physical change when certain con-
ditions were fulfilled — does not even render such an advance
improbable, if there are any general arguments to be adduced
in its favour. Such a cause, I believe, does exist ; and I
shall now endeavour to point out its nature and its mode of
operation.

Outline of the Theory of Natural Selection

In order to make my argument intelligible, it is necessary
for me to explain very briefly the theory of natural selec-
tion promulgated by Mr. Darwin, and the power which it
possesses of modifying the forms of animals and plants. The
grand feature in the multiplication of organic life is, that
close general resemblance is combined with more or less
individual variation. The child resembles its parents or
ancestors more or less closely in all its peculiarities, deformi-
ties, or beauties ; it resembles them in general more than it
does any other individuals ; yet children of the same parents
are not all alike, and it often happens that they differ very
considerably from their parents and from each other. This
is equally true of man, of all animals, and of all plants.
Moreover, it is found that individuals do not differ from their
parents in certain particulars only, while in all others they
are exact duplicates of them. They differ from them and
from each other in every particular : in form, in size, in
colour ; in the structure of internal as well as of external
organs ; in those subtle peculiarities which produce differences
of constitution, as well as in those still more subtle ones
which lead to modifications of mind and character. In other
words, in every possible way, in every organ, and in every
function, individuals of the same stock vary.

Now, health, strength, and long life are the results of a
harmony between the individual and the universe that sur-
rounds it. Let us suppose that at any given moment this
harmony is perfect. A certain animal is exactly fitted to

vin THE DEVELOPMENT OF HUMAN RACES 171

secure its prey, to escape from its enemies, to resist the
inclemencies of the seasons, and to rear a numerous and
healthy offspring. But a change now takes place. A series
of cold winters, for instance, come on, making food scarce,
and bringing an immigration of some other animals to com-
pete with the former inhabitants of the district. The new
immigrant is swift of foot, and surpasses its rivals in the
pursuit of game ; the winter nights are colder, and require a
thicker fur as a protection, and more nourishing food to keep
up the heat of the system. Our supposed perfect animal is
no longer in harmony with its universe ; it is in danger of
dying of cold or of starvation. But the animal varies in its
offspring. Some of these are swifter than others — they still
manage to catch food enough ; some are hardier and more
thickly furred — they manage in the cold nights to keep warm
enough ; the slow, the weak, and the thinly clad soon die
off. Again and again, in each succeeding generation, the
same thing takes place. By this natural process, which is so
inevitable that it cannot be conceived not to act, those best
adapted to live, live ; those least adapted, die. It is some-
times said that we have no direct evidence of the action of
this selecting power in nature. But it seems to me we have
better evidence than even direct observation would be,
because it is more universal, viz., the evidence of necessity.
It must be so ; for, as all wild animals increase in a geomet-
rical ratio, while their actual numbers remain on the
average stationary, it follows that as many die annually as
are born. If, therefore, we deny natural selection, it can
only be by asserting that, in such a case as I have supposed,
the strong, the healthy, the swift, the well clad, the well
organised animals in every respect, have no advantage over
— do not on the average live longer than — the weak, the
unhealthy, the slow, the ill-clad, and the imperfectly organised
individuals ; and this no sane man has yet been found hardy
enough to assert. But this is not all ; for the offspring on
the average resemble their parents, and the selected portion
of each succeeding » generation will therefore be stronger,
swifter, and more thickly furred than the last ; and if this
process goes on for thousands of generations, our animal will
have again become thoroughly in harmony with the new con-

172 NATURAL SELECTION vm

. ^

ditions in which it is placed. But it will now be a different
creature. It will be not only swifter and stronger, and more
furry — it will also probably have changed in colour, in form,
perhaps have acquired a longer tail, or differently shaped
ears ; for it is an ascertained fact that when one part of an
animal is modified, some other parts almost always change,
as it were in sympathy with it. Mr. Darwin calls this
" correlation of growth," and gives as instances that hairless
dogs have imperfect teeth ; white cats, when blue-eyed, are
deaf ; small feet accompany short beaks in pigeons ; and other
equally interesting cases.

Grant, therefore, the premises : 1st, That peculiarities of
every kind are more or less hereditary; 2d, That the off-
spring of every animal vary more or less in all parts of their
organisation ; 3d, That the universe in which these animals
live is not absolutely invariable ; — none of which proposi-
tions can be denied ; and then consider that the animals in
any country (those at least which are not dying out) must at
each successive period be brought into harmony with the
surrounding conditions ; and we have all the elements for a
change of form and structure in the animals, keeping exact
pace with changes of whatever nature in the surrounding
universe. Such changes must be slow, for the changes in the
universe are very slow ; but just as these slow changes be-
come important, when we look at results after long periods
of action, — as we do when we perceive the alterations of the
earth's surface during geological epochs, — so the parallel
changes in animal form become more and more striking, in
proportion as the time they have been going on is great ; as
we see when we compare our living animals with those
which we disentomb from each successively older geological
formation.

This is, briefly, the theory of natural selection, which
explains the changes in the organic world as being parallel
with, and in part dependent on, those in the inorganic. What
we now have to inquire is, Can this theory be applied in
any way to the question of the origin of the races of man 1 or
is there anything in human nature that takes him out of the
category of those organic existences over whose successive
mutations it has had such powerful sway ?

THE DEVELOPMENT OF HUMAN RACES 173

Different Effects of Natural Selection on Animals and on Man

In order to answer these questions, we must consider why
it is that natural selection acts so powerfully upon animals,
and we shall, I believe, find that its effect depends mainly
upon their self-dependence and individual isolation. A slight
injury, a temporary illness, will often end in death, because
it leaves the individual powerless against its enemies. If an
herbivorous animal is a little sick and has not fed well for a
day or two, and the herd is then pursued by a beast of prey,
our poor invalid inevitably falls a victim. So, in a carnivor-
ous animal, the least deficiency of vigour prevents its captur-
ing food, and it soon dies of starvation. There is, as a
general rule, no mutual assistance between adults, which
enables them to tide over a period of sickness. Neither is
there any division of labour ; each must fulfil all the con-
ditions of its existence, and, therefore, natural selection
keeps all up to a pretty uniform standard.

But in man, as we now behold him, this is different. He
is social and sympathetic. In the rudest tribes the sick are
assisted, at least with food ; less robust health and vigour
than the average does not entail death. Neither does the
want of perfect limbs or other organs produce the same effects
as among animals. Some division of labour takes place ; the
swiftest hunt, the less active fish, or gather fruits ; food is, to
some extent, exchanged or divided. The action of natural
selection is therefore checked ; the weaker, the dwarfish, those
of less active limbs, or less piercing eyesight, do not suffer the
extreme penalty which falls upon animals so defective.

In proportion as these physical characteristics become of
less importance, mental and moral qualities will have increas-
ing influence on the well-being of the race. Capacity for
acting in concert for protection, and for the acquisition of
food and shelter ; sympathy, which leads all in turn to assist
each other; the sense of right, which checks depredations
upon our fellows ; the smaller development of the combative
and destructive propensities ; self-restraint in present appe-
tites, and that intelligent foresight which prepares for the
future, are all qualities that from their earliest appearance
must have been for the benefit of each community, and would,

174 NATURAL SELECTION vin

. — ^jj

therefore, have become the subjects of natural selection.
For it is evident that such qualities would be for the well-
being of man, would guard him against external enemies,
against internal dissensions, and against the effects of incle-
ment seasons and impending famine, more surely than could
any merely physical modification. Tribes in which such
mental and moral qualities were predominant would there-
fore have an advantage in the struggle for existence over
other tribes in which they were less developed — would live
and maintain their numbers, while the others would decrease
and finally succumb.

Again, when any slow changes of physical geography or
of climate make it necessary for an animal to alter its food,
its clothing, or its weapons, it can only do so by the occur-
rence of a corresponding change in its own bodily structure
and internal organisation. If a larger or more powerful
beast is to be captured and devoured, as when' a carnivorous
animal which has hitherto preyed on antelopes is obliged from
their decreasing numbers to attack buffaloes, it is only the
strongest who can hold, — those with most powerful claws
and formidable canine teeth that can struggle with and over-
come such an animal. Natural selection immediately comes
into play, and by its action these organs gradually become
adapted to their new requirements. But man, under similar
circumstances, does not require longer nails or teeth, greater
bodily strength or swiftness. He makes sharper spears, or a
better bow, or he constructs a cunning pitfall, or combines in
a hunting party to circumvent his new prey. The capacities
which enable him to do this are what he requires to be
strengthened, and these will, therefore, be gradually modified
by natural selection, while the form and structure of his
body will remain unchanged. So, when a glacial epoch comes
on, some animals must acquire warmer fur, or a covering of
fat, or else die of cold. Those best clothed by nature are,
therefore, preserved by natural selection. Man, under the
same circumstances, will make himself warmer clothing, and
build better houses, and the necessity of doing this will react
upon his mental organisation and social condition — will ad-
vance them while his natural body remains naked as before.

When the accustomed food of some animal becomes scarce

via THE DEVELOPMENT OF HUMAN RACES 175

or totally fails, it can only exist by becoming adapted to a new
kind of food, a food perhaps less nourishing and less digestible.
Natural selection will now act upon the stomach and intes-
tines, and all their individual variations will be taken advan-
tage of, to modify the race into harmony with its new food.
In many cases, however, it is probable that this cannot be
done. The internal organs may not vary quick enough, and
then the animal will decrease in numbers and finally become
extinct. But man guards himself from such accidents by
superintending and guiding the operations of nature. He
plants the seed of his most agreeable food, and thus procures
a supply, independent of the accidents of varying seasons or
natural extinction. He domesticates animals, which serve him
either to capture food or for food itself, and thus changes of
any great extent in his teeth or digestive organs are rendered
unnecessary. Man, too, has everywhere the use of fire, and
by its means can render palatable a variety of animal and
vegetable substances, which he could hardly otherwise make
use of, and thus obtains for himself a supply of food far
more varied and abundant than that which any animal can
command.

Thus man, by the mere capacity of clothing himself, and
making weapons and tools, has taken away from nature that
power of slowly but permanently changing the external form
and structure in accordance with changes in the external
world, which she exercises over all other animals. As the
competing races by which they are surrounded — the climate,
the vegetation, or the animals which serve them for food — are
slowly changing, they must undergo a corresponding change
in their structure, habits, and constitution to keep them in
harmony with the new conditions — to enable them to live
and maintain their numbers. But man does this by means
of his intellect alone, the variations of which enable him, with
an unchanged body, still to keep in harmony with the changing
universe.

There is one point, however, in which nature will still act
upon him as it does on animals, and, to some extent, modify
his external characters. Mr. Darwin has shown that the colour
of the skin is correlated with constitutional peculiarities both
in vegetables and animals, so that liability to certain diseases

176 NATURAL SELECTION vm

or freedom from them is often accompanied by marked external
characters. Now, there is every reason to believe that this
has acted, and, to some extent, may still continue to act on
man. In localities where certain diseases are prevalent, those
individuals of savage races which were subject to them would
rapidly die off, while those who were constitutionally free
from the disease would survive, and become the progenitors
of a new race. These favoured individuals would probably
be distinguished by peculiarities of colour, with which again
peculiarities in the texture or the abundance of hair seem to
be correlated, and thus may have been brought about those
racial differences of colour which seem to have little relation
to mere temperature or other obvious peculiarities of climate.
From the time, therefore, when the social and sympathetic
feelings came into active operation, and the intellectual and
moral faculties became fairly developed, man would cease to
be influenced by natural selection in his physical form and
structure. As an animal he would remain almost stationary,
the changes of the surrounding universe ceasing to produce in
him that powerful modifying effect which they exercise over
other parts of the organic world. But from the moment that
the form of his body became stationary, his mind would
become subject to those very influences from which his body
had escaped ; every slight variation in his mental and moral
nature which should enable him better to guard against
adverse circumstances, and combine for mutual comfort and
protection, would be preserved and accumulated ; the better
and higher specimens of our race would therefore increase and
spread, the lower and more brutal would give way and suc-
cessively die out, and that rapid advancement of mental
organisation would occur which has raised the very lowest
races of man so far above the brutes (although differing so
little from some of them in physical structure), and, in con-
junction with scarcely perceptible modifications of form, has
developed the wonderful intellect of the European races.

Influence of external Nature in the development of the

Human Mind

But from the time when this mental and moral advance
commenced, and man's physical character became fixed and

vin THE DEVELOPMENT OF HUMAN RACES 177

almost immutable, a new series of causes would come into
action and take part in his mental growth. The diverse aspects
of nature would now make themselves felt, and profoundly
influence the character of the primitive man.

When the power that had hitherto modified the body had
its action transferred to the mind, then races would advance
and become improved, merely by the harsh discipline of a
sterile soil and inclement seasons. Under their influence a
hardier, a more provident, and a more social race would be
developed than in those regions where the earth produces a
perennial supply of vegetable food, and where neither fore-
sight nor ingenuity are required to prepare for the rigours of
winter. And is it not the fact that in all ages, and in every
quarter of the globe, the inhabitants of temperate have been
superior to those of hotter countries ? All the great invasions
and displacements of races have been from North to South,
rather than the reverse ; and we have no record of there ever
having existed, any more than there exists to-day, a solitary
instance of an indigenous inter -tropical civilisation. The
Mexican civilisation and government came from the North,
and, as well as the Peruvian, was established, not in the rich
tropical plains, but on the lofty and sterile plateau:: of the
Andes. The religion and civilisation of Ceylon were intro-
duced from North India ; the successive conquerors of the
Indian peninsula came from the North-west; the northern
Mongols conquered the more Southern Chinese ; and it was
the bold and adventurous tribes of the North that overran
and infused new life into Southern Europe.

Extinction of Lower Races

It is the same great law of " the preservation of favoured
races in the struggle for life," which leads to the inevitable
extinction of all those low and mentally undeveloped popula-
tions with which Europeans come in contact. The red Indian
in North America and in Brazil ; the Tasmanian, Australian,
and New Zealander in the southern hemisphere, die out, not
from any one special cause, but from the inevitable effects
of an unequal mental and physical struggle. The intellectual
and moral, as well as the physical, qualities of the European
are superior ; the same powers and capacities which have
N

178 NATURAL SELECTION j- vni

made him rise in a few centuries from the condition of the
wandering savage, with a scanty and stationary population, to
his present state of culture and advancement, with a greater
average longevity, a greater average strength, and a capacity
of more rapid increase, — enable him when in contact with the
savage man to conquer in the struggle for existence, and to
increase at his expense, just as the better adapted increase at
the expense of the less adapted varieties in the animal and
vegetable kingdoms — just as the weeds of Europe overrun
North America and Australia, extinguishing native produc-
tions by the inherent vigour of their organisation, and by
their greater capacity for existence and multiplication.

The Origin of the Races of Man

If these views are correct, — if in proportion as man's social,
moral, and intellectual faculties became developed, his physical
structure would cease to be affected by the operation of
natural selection, — we have a most important clue to the
origin of races. For it will follow that those great modifica-
tions of structure and of external form, which resulted in the
development of man out of some lower type of animal, must
have occurred before his intellect had raised him above the
condition of the brutes, at a period when he was gregarious,
but scarcely social, with a mind perceptive but not reflective,
ere any sense of right or feelings of sympathy had been
developed in him. He would be still subject, like the rest of
the organic world, to the action of natural selection, which
would retain his physical form and constitution in harmony
with the surrounding universe. He was probably at a very
early period a dominant race, spreading widely over the
warmer regions of the earth as it then existed, and in agree-
ment with what we see in the case of other dominant species,
gradually becoming modified in accordance with local con-
ditions. As he ranged farther from his original home, and
became exposed to greater extremes of climate, to greater
changes of food, and had to contend with new enemies, organic
and inorganic, slight useful variations in his constitution
would be selected and rendered permanent, and would, on
the principle of " correlation of growth," be accompanied by
corresponding external physical changes. Thus might have

viii THE DEVELOPMENT OF HUMAN RACES 179

arisen those striking characteristics and special modifications
which still distinguish the chief races of mankind. The red,
black, yellow, or blushing white skin ; the straight, the curly,
the woolly hair; the scanty or 'abundant beard; the straight
or oblique eyes ; the various forms of the pelvis, the cranium,
and other parts of the skeleton.

But while these changes had been going on, his mental
development had, from some unknown cause, greatly advanced,
and had now reached that condition in which it began power-
fully to influence his whole existence, and would therefore
become subject to the irresistible action of natural selection.
This action would quickly give the ascendency to mind :
speech would probably now be first developed, leading to a
still further advance of the mental faculties ; and from that
moment man, as regards the form and structure of most parts
of his body, would remain almost stationary. The art of
making weapons, division of labour, anticipation of the future,
restraint of the appetites, moral, social, and sympathetic feel-
ings, would now have a preponderating influence on his well-
being, and would therefore be that part of his nature on
which natural selection would most powerfully act; and
we should thus have explained that wonderful persistence of
mere physical characteristics which is the stumbling-block of
those who advocate the unity of mankind.

We are now, therefore, enabled to harmonise the conflict-
ing views of anthropologists on this subject. Man may have
been — indeed I believe must have been — once a homogeneous
race ; but it was at a period of which we have as yet dis-
covered no remains — at a period so remote in his history that
he had not yet acquired that wonderfully developed brain,
the organ of the mind, which now, even in his lowest examples,
raises him far above the highest brutes — at a period when
he had the form but hardly the nature of man, when he
neither possessed human speech, nor those sympathetic and
moral feelings which in a greater or less degree everywhere
now distinguish the race. Just in proportion as these truly
human faculties became developed in him would his physical
features become fixed and permanent, because the latter would
be of less importance to his well-being ; he would bo kept in
harmony with the slowly changing universe around him, by

NATURAL SELECTION

an advance in mind rather than by a change in body. If,
therefore, we are of opinion that he was not really man till
these higher faculties were fully developed, we may fairly
assert that there were many originally distinct races of men ;
while, if we think that a being closely resembling us in form
and structure, but with mental faculties scarcely raised above
the brute, must still be considered to have been human, we
are fully entitled to maintain the common origin of all man-
kind.

The Bearing of these Views on the Antiquity of Man
These considerations, it will be seen, enable us to place the
origin of man at a much more remote geological epoch than
has yet been thought possible. He may even have lived in
the Miocene or Eocene period, when not a single other
mammal was identical in form with any existing species.
For, in the long series of ages during which these primeval
animals were being slowly changed into the species which now
inhabit the earth, the power which acted to modify them
would only affect the mental organisation of man. His brain
alone would have increased in size and complexity, and his
cranium have undergone corresponding changes of form, while
the whole structure of lower animals was being changed.
This will enable us to understand how the fossil crania of
Denise and Engis agree so closely with existing forms, al-
though they undoubtedly existed in company with large
mammalia now extinct. The Neanderthal skull may be a
specimen of one of the lowest races then existing, just as the
Australians are the lowest of our modern epoch. We have
no reason to suppose that mind and brain and skull modifica-
tion could go on quicker than that of the other parts of the
organisation ; and we must therefore look back very far in
the past to find man in that early condition in which his
mind was not sufficiently developed, to remove his body from
the modifying influence of external conditions and the cumu-
lative action of natural selection. I believe, therefore, that
there is no a priori reason against our finding the remains of
man or his works in the tertiary deposits. The absence of
all such remains in the European beds of this age has little
weight, because, as we go farther back in time, it is natural

vin .THE DEVELOPMENT OF HUMAN RACES 181

to suppose that man's distribution over the surface of the
earth was less universal than at present.

Besides, Europe was in a great measure submerged during
the tertiary epoch ; and though its scattered islands may have
been uninhabited by man, it by no means follows that he did
not at the same time exist in warm or tropical continents. If
geologists can point out to us the most extensive land in the
warmer regions of the earth, which has not been submerged
since Eocene or Miocene times, it is there that we may expect
to find some traces of the very early progenitors of man. It
is there that we may trace back the gradually decreasing
.brain of former races, till we come to a time when the body
also begins materially to differ. Then we shall have reached
the starting-point of the human family. Before that period
he had not mind enough to preserve his body from change,
and would, therefore, have been subject to the same com-
paratively rapid modifications of form as the other mammalia.

Their Bearing on the Dignity and Supremacy of Man
If the views I have here endeavoured to sustain have any
foundation, they give us a new argument for placing man
apart, as not only the head and culminating point of the grand
series of organic nature, but as in some degree a new and dis-
tinct order of being. From those infinitely remote ages, when
the first rudiments of organic life appeared upon the earth,
every plant and every animal has been subject to one great
law of physical change. As the earth has gone through its
grand cycles of geological, climatal, and organic progress,
every form of life has been subject to its irresistible action,
and has been continually but imperceptibly moulded into
such new shapes as would preserve their harmony with the
ever-changing universe. No living thing could escape this
law of its being ; none (except, perhaps, the simplest and most
rudimentary organisms) could remain unchanged and live,
amid the universal change around it.

At length, however, there came into existence a being in
whom that subtle force we term mind, became of greater
importance than his mere bodily structure. Though with a
naked and unprotected body, this gave him clothing against
the varying inclemencies of the seasons. Though unable to

182 NATURAL SELECTION y vni

compete with the deer in swiftness, or with the wild bull in
strength, this gave him weapons with which to capture or
overcome both. Though less capable than most other animals
of living on the herbs and the fruits that unaided nature sup-
plies, this wonderful faculty taught him to govern and direct
nature to his own benefit, and make her produce food for him,
when and where he pleased. From the moment when the
first skin was used as a covering, when the first rude spear
was formed to assist in the chase, when fire was first used to
cook his food, when the first seed was sown or shoot planted,
a grand revolution was effected in nature — a revolution which
in all the previous ages of the earth's history had had no
parallel, for a being had arisen who was no longer necessarily
subject to change with the changing universe — a being who
was in some degree superior to nature, inasmuch as he knew
how to control and regulate her action, and could keep him-
self in harmony with her, not by a change in body, but by an
advance of mind.

Here, then, we see the true grandeur and dignity of man.
On this view of his special attributes, we may admit that
even those who claim for him a position as an order, a class,
or a sub-kingdom by himself, have some show of reason on
their side. He is, indeed, a being apart, since he is not in-
fluenced by the great laws which irresistibly modify all other
organic beings. Nay more : this victory which he has gained
for himself, gives him a directing influence over other exist-
ences. Man has not only escaped natural selection him-
self, but he is actually able to take away some of that power
from nature which before his appearance she universally
exercised. We can anticipate the time when the earth will
produce only cultivated plants and domestic animals ; when
man's selection shall have supplanted natural selection ;
and when the ocean will be the only domain in which that
power can be exerted, which for countless cycles of ages has
ruled supreme over all the earth.

Their Bearing on the future Development of Man
We now find ourselves enabled to answer those who main-
tain that if Mr. Darwin's theory of the Origin of Species is
true, man too must change in form, and become developed

vin THE DEVELOPMENT OF HUMAN RACES 183

into some other animal as different from his present self as he
is from the gorilla or the chimpanzee ; and who speculate on
what this form is likely to be. But it is evident that such
will not be the case ; for no change of conditions is con-
ceivable which will render any important alteration of his
form and organisation so universally useful and necessary to
him, as to give those possessing it always the best chance of
surviving, and thus lead to the development of a new species,
genus, or higher group of man. On the other hand, we
know that far greater changes of conditions and of his entire
environment have been undergone by man than any other
highly organised animal could survive unchanged, and have
been met by mental, not corporeal adaptation. The difference
of habits, of food, clothing, weapons, and enemies between
savage and civilised man is enormous. Difference in bodily
form and structure there is practically none, except a slightly
increased size of brain, corresponding to his higher mental
development.

We have every reason to believe, then, that man may
have existed, and may continue to exist, through a series of
geological periods which shall see all other forms of animal
life again and again changed ; while he himself remains un-
changed, except in the two particulars already specified — the
head and face, as immediately connected with the organ of
the mind and as being the medium of expressing the most
refined emotions of his nature, — and to a slight extent in
colour, hair, and proportions, so far as they are correlated
with constitutional resistance to disease.

Summary

Briefly to recapitulate the argument; — in two distinct
ways has man escaped the influence of those laws which have
produced unceasing change in the animal world. 1. By his
superior intellect he is enabled to provide himself with cloth-
ing and weapons, and by cultivating the soil to obtain a con-
stant supply of congenial food. This renders it unnecessary
for his body to be modified in accordance with changing con-
ditions— to gain a warmer natural covering, to acquire more
powerful teeth or claws, or to become adapted to obtain and
digest new kinds of food, as circumstances may require. 2.

184 NATURAL SELECTION vin

By his superior sympathetic and moral feelings he becomes
fitted for the social state ; he ceases to plunder the weak and
helpless of his tribe ; he shares the game which he has caught
with less active or less fortunate hunters, or exchanges it for
weapons which even the weak or the deformed can fashion ;
he saves the sick and wounded from death ; and thus the
power which leads to the rigid destruction of all animals who
cannot in every respect help themselves, is prevented from
acting on him.

This power is natural selection ; and, as by no other
means can it be shown that individual variations can ever
become accumulated and rendered permanent, so as to form
well-marked races, it follows that the differences which now
separate mankind from other animals must have been pro-
duced before he became possessed of a human intellect or
human sympathies. This view also renders possible, or even
requires, the existence of man at a comparatively remote
geological epoch. For, during the long periods in which other
animals have been undergoing modification in their whole
structure, to such an amount as to constitute distinct genera
and families, man's body will have remained genetically, or even
specifically, the same, while his head and brain alone will have
undergone modification equal to theirs. We can thus under-
stand how it is that, judging from the head and brain, Pro-
fessor Owen places man in a distinct sub-class of mammalia,
while as regards the bony structure of his body, there is the
closest anatomical resemblance to the anthropoid apes, " every
tooth, every bone, strictly homologous — which makes the
determination of the difference between Homo and Pitliecus
the anatomist's difficulty." The present theory fully recog-
nises and accounts for these facts ; and we may perhaps
claim as corroborative of its truth that it neither requires us
to depreciate the intellectual chasm which separates man from
the apes, nor refuses full recognition of the striking resem-
blances to them, which exist in other parts of his structure.

In concluding this brief sketch of a great subject, I would
point out its bearing upon the future of the human race. If my
conclusions are just, it must inevitably follow that the higher

vin THE DEVELOPMENT OF HUMAN RACES 185

— the more intellectual and moral — must displace the lower
and more degraded races ; and the power of " natural selec-
tion," still acting on his mental organisation, must ever lead
to the more perfect adaptation of man's higher faculties to
the conditions of surrounding nature, and to the exigencies
of the social state. While his external form will probably
ever remain unchanged, except in the development of that
perfect beauty which results from a healthy and well organised
body, refined and ennobled by the highest intellectual faculties
and sympathetic emotions, his mental constitution may con-
tinue to advance and improve, till the world is again inhabited
by a single nearly homogeneous race, no individual of which
will be inferior to the noblest specimens of existing humanity.
Our progress towards such a result is very slow, but it
still seems to be a progress. We are just now living at an
abnormal period of the world's history, owing to the marvel-
lous developments and vast practical results of science having
been given to societies too low morally and intellectually to
know how to make the best use of them, and to whom they
have consequently been curses as well as blessings. Among
civilised nations at the present day it does not seem possible
for natural selection to act in any way, so as to secure the
permanent advancement of morality and intelligence ; for it is
indisputably the mediocre, if not the low, both as regards
morality and intelligence, who succeed best in life and multiply
fastest. Yet there is undoubtedly an advance — on the whole
a steady and a permanent one — both in the influence on public
opinion of a high morality, and in the general desire for in-
tellectual elevation ; and as I cannot impute this in any way
to " survival of the fittest," I am forced to conclude that it
is due to the inherent progressive power of those glorious
qualities which raise us so immeasurably above our fellow
animals, and at the same time afford us the surest proof that
there are other and higher existences than ourselves, from
whom these qualities may have been derived, and towards
whom we may be ever tending.

IX

THE LIMITS OF NATURAL SELECTION AS APPLIED TO MAN

THROUGHOUT this volume I have endeavoured to show that
the known laws of variation, multiplication, and heredity,
resulting in a " struggle for existence " and the " survival of
the fittest," have probably sufficed to produce all the varieties
of structure, all the wonderful adaptations, all the beauty of
form and of colour, that we see in the animal and vegetable
kingdoms. To the best of my ability I have answered the
most obvious and the most often repeated objections to this
theory, and have, I hope, added to its general strength,
by showing how colour — one of the strongholds of the ad-
vocates of special creation — may be, in almost all its modifi-
cations, accounted for by the combined influence of sexual
selection and the need of protection.1 I have also endeavoured
to show how the same power which has modified animals has
acted on man ; and have, I believe, proved that, as soon as
the human intellect became developed above a certain low
stage, man's body would cease to be materially affected by
natural selection, because the development of his mental
faculties would render important modifications of its form
and structure unnecessary. It will, therefore, probably ex-
cite some surprise among my readers to find that I do not
consider that all nature can be explained on the principles of
which I am so ardent an advocate ; and that I am now myself
going to state objections, and to place limits, to the power of
natural selection. I believe, however, that there are such

1 Since writing this in 1870 I have come to the conclusion that sexual
selection has had little, if any, influence on colour. See chap. v. of " Tropi-
cal Nature " in this volume, and Dantnnism, chap. x.

ix LIMITS OF NATURAL SELECTION IN MAN 187

limits ; and that just as surely as we can trace the action of
natural laws in the development of organic forms, and can
clearly conceive that fuller knowledge would enable us to
follow step by step the whole process of that development, so
surely can we trace the action of some unknown higher law,
beyond and independent of all those laws of which we have
any knowledge. We can trace this action more or less dis-
tinctly in many phenomena, the two most important of which
are — the origin of sensation or consciousness, and the develop-
ment of man from the lower animals. I shall first consider
the latter difficulty as more immediately connected with the
subjects discussed in this volume.

WJrnt Natural Sehctim can Not do

In considering the question of the development of man by
known natural laws, we must ever bear in mind the first prin-
ciple of natural selection, no less than of the general theory
of evolution, that all changes of form or structure, all increase
in the size of an organ or in its complexity, all greater special-
isation or physiological division of labour, can only be brought
about in as much as it is for the good of the being so modi-
fied. Mr. Darwin himself has taken care to impress upon us
that natural selection has no power to produce absolute
perfection, but only relative perfection, — no power to advance
any being much beyond his fellow beings, but only just so
much beyond them as to enable it to survive them in the
struggle for existence. Still less has it any power to produce
modifications which are in any degree injurious to its pos-
sessor, and Mr. Darwin frequently uses the strong expression,
that a single case of this kind would be fatal to his theory.
If, therefore, we find in man any characters, which all the
evidence we can obtain goes to show would have been actually
injurious to him on their first appearance, they could not
possibly have been produced by natural selection. Neither
could any specially developed organ have been so produced
if it had been merely useless to him, or if its use were not
proportionate to its degree of development. Such cases as
these would prove that some other law, or some other power,
than natural selection had been at work. But if, further,
we could see that these very modifications, though hurtful or

188 NATURAL SELECTION ix

useless at the time when they first appeared, became in the
highest degree useful at a much later period, and are now
essential to the full moral and intellectual development of
human nature, we should then infer the action of mind,
foreseeing the future and preparing for it, just as surely as
we do, when we see the breeder set himself to work with the
determination to produce a definite improvement in some culti-
vated plant or domestic animal. I would further remark that
this inquiry is as thoroughly scientific and legitimate as that
into the origin of species itself. It is an attempt to solve
the inverse problem, to deduce the existence of a new power
of a definite character, in order to account for facts which,
according to the theory of natural selection, ought not to
happen. Such problems are well known to science, and the
search after their solution has often led to the most brilliant
results. In the case of man, there are facts of the nature
above alluded to, and in calling attention to them, and in
inferring a cause for them, I believe that I am as strictly
within the bounds of scientific investigation as I have been
in any other portion of my work.

The Brain of the Savage shown to be Larger than he Needs it to be
Size of Brain an important Element of Mental Power. — The
brain is universally admitted to be the organ of the mind ;
and it is almost as universally admitted that size of brain is
one of the most important of the elements which determine
mental power or capacity. There seems to be no doubt that
brains differ considerably in quality, as indicated by greater
or less complexity of the convolutions, quantity of gray
matter, and perhaps unknown peculiarities of organisation ;
but this difference of quality seems merely to increase or
diminish the influence of quantity, not to neutralise it.
Thus, all the most eminent modern writers see an intimate
connection between the diminished size of the brain in the
lower races of mankind, and their intellectual inferiority.
The collections of Dr. J. B. Davis and Dr. Morton give the
following as the average internal capacity of the cranium in
the chief races : Teutonic family, 94 cubic inches ; Esquimaux,
91 cubic inches; Negroes, 85 cubic inches; Australians and Tas-
manians, 82 cubic inches ; Bushmen, 77 cubic inches. These

ix LIMITS OF NATURAL SELECTION IN MAN 189

last numbers, however, are deduced from comparatively few speci-
mens, and may be below the average, just as a small number of
Finns and Cossacks give 98 cubic inches, or considerably more
than that of the German races. It is evident, therefore, that the
absolute bulk of the brain is not necessarily much less in savage
than in civilised man, for Esquimaux skulls are known with a
capacity of 1 1 3 inches, or hardly less than the largest among
Europeans. But what is still more extraordinary, the few
remains yet known of prehistoric man do not indicate any
material diminution in the size of the brain case. A Swiss
skull of the stone age, found in the lake dwelling of Meilen,
corresponded exactly to that of a Swiss youth of the present
day. The celebrated Neanderthal skull had a larger circum-
ference than the average, and its capacity, indicating actual
mass of brain, is estimated to have been not less than 75
cubic inches, or nearly the average of existing Australian
crania. The Engis skull, perhaps the oldest known, and
which, according to Sir John Lubbock, "there seems no doubt
was really contemporary with the mammoth and the cave
bear," is yet, according to Professor Huxley, " a fair average
skull, which might have belonged to a philosopher, or might
have contained the thoughtless brains of a savage." Of the
cave men of Les Eyzies, who were undoubtedly contemporary
with the reindeer in the south of France, Professor Paul
Broca says (in a paper read before the Congress of Pre-
historic Archaeology in 1868): "The great capacity of the
brain, the development of the frontal region, the fine elliptical
form of the anterior part of the profile of the skull, are incon-
testible characteristics of superiority, such as we are accus-
tomed to meet with in civilised races ; " yet the great breadth
of the face, the enormous development of the ascending ramus
of the lower jaw, the extent and roughness of the surfaces for
the attachment of the muscles, especially of the masticators,
and the extraordinary development of the ridge of the femur,
indicate great muscular power, and the habits of a savage and
brutal race.

These facts might almost make us doubt whether the size
of the brain is in any direct way an index of mental power,
had we not the most conclusive evidence that it is so, in the
fact that, whenever an adult male European has a skull less

190 NATURAL SELECTION ix

than 19 inches in circumference, or has less than 65 cubic inches
of brain, he is invariably idiotic. When we join with this the
equally undisputed fact that great men, — those who combine
acute perception with great reflective power, strong passions,
and general energy of character, such as Napoleon, Cuvier, and
O'Connell, — have always heads far above the average size, we
must feel satisfied that volume of brain is one, and perhaps the
most important, measure of intellect ; and this being the case,
we cannot fail to be struck with the apparent anomaly that
many of the lowest savages should have as much brains as
average Europeans. The idea is suggested of a surplusage of
power — of an instrument beyond the needs of its possessor.

Comparison of the Brains of Man and of Anthropoid Apes. —
In order to discover if there is any foundation for this notion,
let us compare the brain of man with that of animals. The
adult male orang-utan is quite as bulky as a small sized man,
while the gorilla is considerably above the average size of
man, as estimated by bulk and weight ; yet the former has a
brain of only 28 cubic inches, the latter, one of 30, or, in the
largest specimen yet known, of 34 J cubic inches. We have
seen that the average cranial capacity of the lowest savages is
probably not less than five-sixths of that of the highest civilised
races, while the brain of the anthropoid apes scarcely amounts
to one-third of that of man, in both cases taking the average ;
or the proportions may be more clearly represented by the
following figures : Anthropoid apes, 1 0 ; savages, 26; civilised
man, 32. But do these figures at all approximately represent
the relative intellect of the three groups ? Is the savage really
no further removed from the philosopher, and so much removed
from the ape, as these figures would indicate ? In considering
this question, we must not forget that the heads of savages vary
in size almost as much as those of civilised Europeans. Thus,
while the largest Teutonic skull in Dr. Da vis's collection is 1 1 2 -4
cubic inches, there is an Araucanian of 1 1 5 '5, an Esquimaux of
113-1, a Marquesan of HO'6, a Negro of 105 '8, and even an
Australian of 104 '5 cubic inches. We may, therefore, fairly
compare the savage with the highest European on the one side,
and with the orang, chimpanzee, or gorilla, on the other,
and see whether there is any relative proportion between
brain and intellect.

ix LIMITS OF NATURAL SELECTION IN MAN 191

Range of Intellectual Power in Man. — First, let us consider
what this wonderful instrument, the brain, is capable of in
its higher developments. In Mr. Galton's interesting work
on Hereditary Genius, he remarks on the enormous differ-
ence between the intellectual power and grasp of the well-
trained mathematician or man of science, and the average
Englishman. The number of marks obtained by high
wranglers is often more than thirty times as great as that
of the men at the bottom of the honour list, who are still
of fair mathematical ability ; and it is the opinion of skilled
examiners that even this does not represent the full difference
of intellectual power. If, now, we descend to those savage
tribes who only count to three or five, and who find it im-
possible to comprehend the addition of two and three without
having the objects actually before them, we feel that the
chasm between them and the good mathematician is so vast
that a thousand to one will probably not fully express it.
'Yet we know that the mass of brain might be nearly the
same in both, or might not differ in a greater proportion than
as 5 to 6 ; whence we may fairly infer that the savage pos-
sesses a brain capable, if cultivated and developed, of per-
forming work of a kind and degree far beyond what he ever
requires it to do.

Again, let us consider the power of the higher or even the
average civilised man, of forming abstract ideas, and carrying
on more or less complex trains of reasoning. Our languages
are full of terms to express abstract conceptions. Our busi-
ness and our pleasures involve the continual foresight of many
contingencies. Our law, our government, and our science
continually require us to reason through a variety of compli-
cated phenomena to the expected result. Even our games,
such as chess, compel us to exercise all these faculties in a
remarkable degree. Compare this with the savage languages,
which contain no words for abstract conceptions ; the utter
want of foresight of the savage man beyond his simplest
necessities; his inability to combine, or to compare, or to
reason on any general subject that does not immediately
appeal to his senses. So, in his moral and aesthetic faculties,
the savage has none of those wide sympathies with all nature,
those conceptions of the infinite, of the good, of the sublime

192 NATURAL SELECTION-*" ix

and beautiful, which are so largely developed in civilised
man. Any considerable development of these would, in fact,
be useless or even hurtful to him, since they would to some
extent interfere with the supremacy of those perceptive and
animal faculties on which his very existence often depends, in
the severe struggle he has to carry on against nature and his
fellow-man. Yet the rudiments of all these powers and feel-
ings undoubtedly exist in him, since one or other of them
frequently manifest themselves in exceptional cases, or when
some special circumstances call them forth. Some tribes,
such as the Santals, are remarkable for as pure a love of
truth as the most moral among civilised men. The Hindoo
and the Polynesian have a high artistic feeling, the first traces
of which are clearly visible in the rude drawings of the
palseolithic men who were the contemporaries in France of
the reindeer and the mammoth. Instances of unselfish love,
of true gratitude, and of deep religious feeling, sometimes
occur among most savage races.

On the whole, then, we may conclude that the general,
moral, and intellectual development of the savage is not less
removed from that of civilised man than has been shown to
be the case in the one department of mathematics ; and from
the fact that all the moral and intellectual faculties do occa-
sionally manifest themselves, we may fairly conclude that they
are always latent, and that the large brain of the savage man
is much beyond his actual requirements in the savage state.

Intellect of Savages and of Animals compared. — Let us
now compare the intellectual wants of the savage, and the
actual amount of intellect he exhibits, with those of the
higher animals. Such races as the Andaman Islanders,
the Australians, and the Tasmanians, the Digger Indians of
North America, or the natives of Fuegia, pass their lives so
as to require the exercise of few faculties not possessed in an
equal degree by many animals. In the mode of capture of
game or fish they by no means surpass the ingenuity or fore-
thought of the jaguar, who drops saliva into the water, and
seizes the fish as they come to eat it; or of wolves and
jackals, who hunt in packs ; or of the fox, who buries his
surplus food till he requires it. The sentinels placed by
antelopes and by monkeys, and the various modes of building

ix LIMITS OF NATURAL SELECTION IN MAN 193

adopted by field mice and beavers, as well as the sleeping-
place of the orang-utan, and the tree-shelter of some of the
African anthropoid apes, may well be compared with the
amount of care and forethought bestowed by many savages
in similar circumstances. His possession of free and perfect
hands, not required for locomotion, enables man to form and
use weapons and implements which are beyond the physical
powers of brutes ; but having done this, he certainly does not
exhibit more mind in using them than do many lower animals.
What is there in the life of the savage but the satisfying of
the cravings of appetite in the simplest and easiest way?
What thoughts, ideas, or actions are there that raise him
many grades above the elephant or the ape 1 Yet he pos-
sesses, as we have seen, a brain vastly superior to theirs in
size and complexity ; and this brain gives him, in an unde-
veloped state, faculties which he never requires to use. And
if this is true of existing savages, how much more true must
it have been of the men whose sole weapons were rudely
chipped flints, and some of whom, we may fairly conclude,
were lower than any existing race ; while the only evidence
yet in our possession shows them to have had brains fully
as capacious as those of the average of the lower savage
races.

We see, then, that whether we compare the savage with
the higher developments of man, or with the brutes around
him, we are alike driven to the conclusion that in his large and
well -developed brain he possesses an organ quite dispropor-
tionate to his actual requirements — an organ that seems pre-
pared in advance, only to be fully utilised as he progresses in
civilisation. A brain one-half larger than that of the gorilla
would, according to the evidence before us, fully have sufficed
for the limited mental development of the savage ; and we
must therefore admit that the large brain he actually pos-
sesses could never have been solely developed by any of those
laws of evolution, whose essence is, that they lead to a degree
of organisation exactly proportionate to the wants of each
species, never beyond those wants — that no preparation can
be made for the future development of the race — that one
part of the body can never increase in size or complexity, ex-
cept in strict co-ordination to the pressing wants of the whole.
0

194 NATURAL SELECTION ix

The brain of prehistoric and of savage man seems to me to
prove the existence of some power distinct from that which
has guided the development of the lower animals through
their ever-varying forms of being.

The Use of the Hairy Covering of Mammalia
Let us now consider another point in man's organisation,
the bearing of which has been almost entirely overlooked by
writers on both sides of this question. One of the most
general external characters of the terrestrial mammalia is
the hairy covering of the body, which, whenever the skin is
flexible, soft, and sensitive, forms a natural protection against
the severities of climate, and particularly against rain. That
this is its most important function is well shown by the
manner in which the hairs are disposed so as to carry off the
water, by being invariably directed downwards from the most
elevated parts of the body. Thus, on the under surface the
hair is always less plentiful, and, in many cases, the belly is
almost bare. The hair lies downwards, on the limbs of all
walking mammals, from the shoulder to the toes ; but in the
orang-utan it is directed from the shoulder to the elbow, and
again from the wrist to the elbow, in a reverse direction.
This corresponds to the habits of the animal, which, when
resting, holds its long arms upwards over its head, or clasping
a branch above it, so that the rain would flow down both the
arm and forearm to the long hair which meets at the elbow.
In accordance with this principle, the hair is always longer
or more dense along the spine or middle of the back
from the nape to the tail, often rising into a crest of hair
or bristles on the ridge of the back. This character prevails
through the entire series of the mammalia, from the mar-
supials to the quadrumana, and by this long persistence it
must have acquired such a powerful hereditary tendency
that we should expect it to reappear continually even
after it had been abolished by ages of the most rigid
selection; and we may feel sure that it never could have
been completely abolished under the law of natural selec-
tion, unless it had become so positively injurious as to
lead to the almost invariable extinction of individuals
possessing it.

LIMITS OF NATURAL SELECTION IN MAN 195

The constant Absence of Hair from certain parts of Man's

Body a remarkable Phenomenon

In man the hairy covering of the body has almost totally
disappeared, and, what is very remarkable, it has disappeared
more completely from the back than from any other part of
the body. Bearded and beardless races alike have the back
smooth, and even when a considerable quantity of hair
appears on the limbs and breast, the back, and especially the
spinal region, is absolutely free, thus completely reversing
the characteristics of all other mammalia. The Ainos of the
Kurile Islands and Japan are said to be' a hairy race ; but
Mr. Bickmore, who saw some of them, and described them in
a paper read before the Ethnological Society, gives no details
as to where the hair was most abundant, merely stating gene-
rally that "their chief peculiarity is their great abundance
of hair, not only on the head and face, but over the whole
body." This might very well be said of any man who had
hairy limbs and breast, unless it was specially stated that his
back was hairy, which is not done in this case. The hairy
family in Birmah have, indeed, hair on the back rather longer
than on the breast, thus reproducing the true mammalian
character, but they have still longer hair on the face, fore-
head, and inside the ears, which is quite abnormal ; and the
fact that their teeth are all very imperfect shows that this is
a case of monstrosity rather than one of true reversion to the
ancestral type of man before he lost his hairy covering.

Savage Man feels the Want of this Hairy Covering
We must now inquire if we have any evidence to show,
or any reason to believe, that a hairy covering to the back
would be in any degree hurtful to savage man, or to man in
any stage of his progress from his lower animal form ; and
if it were merely useless, could it have been so entirely
and completely removed as not to be continually reappearing
in mixed races ? Let us look to savage man for some light
on these points. One of the most common habits of savages
is to use some covering for the back and shoulders, even when
they have none on any other part of the body. The early
voyagers observed with surprise that the Tasmanians, both

196 NATURAL SELECTION ix

men and women, wore the kangaroo -skin, which was their
only covering, not from any feeling of modesty, but over the
shoulders to keep the back dry and warm. A cloth over the
shoulders was also the national dress of the Maories. The
Patagonians wear a cloak or mantle over the shoulders, and
the Fuegians often wear a small piece of skin on the back,
laced on, and shifted from side to side as the wind blows.
The Hottentots also wore a somewhat similar skin over the
back, which they never removed, and in which they were
buried. Even in the tropics most savages take precautions
to keep their backs dry. The natives of Timor use the leaf
of a fan palm, carefully stitched up and folded, which they
always carry with them, and which, held over the back, forms
an admirable protection from the rain. Almost all the Malay
races, as well as the Indians of South America, make great
palm-leaf hats, four feet or more across, which they use during
their canoe voyages to protect their bodies from heavy showers
of rain ; and they use smaller hats of the same kind when
travelling by land.

We find, then, that so far from there being any reason to
believe that a hairy covering to the back could have been
hurtful or even useless to prehistoric man, the habits of
modern savages indicate exactly the opposite view, as they
evidently feel the want of it, and are obliged to provide
substitutes of various kinds. The perfectly erect posture of
man may be supposed to have something to do with the dis-
appearance of the hair from his body while it remains on his
head ; but when walking, exposed to rain and wind, a man
naturally stoops forwards and thus exposes his back ; and the
undoubted fact that most savages feel the effects of cold and
wet most severely in that part of the body, sufficiently demon-
strates that the hair could not have ceased to grow there merely
because it was useless, even if it were likely that a character
so long persistent in the entire order of mammalia could have
so completely disappeared under the influence of so weak a
selective power as a diminished usefulness.

Man's Naked Skin could not have been produced by Natural Selection

It seems to me, then, to be absolutely certain that natural

selection could not have produced man's hairless body by

ix LIMITS OF NATURAL SELECTION IN MAN 197

the accumulation of variations from a hairy ancestor. The
evidence all goes to show that such variations could not have
been useful, but must, on the contrary, have been to some
extent hurtful. If even, owing to an unknown correlation
with other hurtful qualities, it had been abolished in the
ancestral tropical man, we cannot conceive that, as man
spread into colder climates, it should not have returned under
the powerful influence of reversion to such a long persistent
ancestral type. But the very foundation of such a supposi-
tion as this is untenable, for we cannot suppose that a
character which, like hairiness, exists throughout the whole
of the mammalia, can have become, in one form only, so
constantly correlated with an injurious character as to lead to
its permanent suppression — a suppression so complete and
effectual that it never, or scarcely ever, reappears in mongrels
of the most widely different races of man.

Two characters could hardly be wider apart than the size
and development of man's brain and the distribution of hair
upon the surface of his body, yet they both lead us to the
same conclusion — that some other power than natural selec-
tion has been engaged in his production.

Feet and Hands of Man, considered as Difficulties on

the Theory of Natural Selection

There are a few other physical characteristics of man that
may just be mentioned as offering similar difficulties, though
I do not attach the same importance to them as to those I
have already dwelt on. The specialisation and perfection of
the hands and feet of man seems difficult to account for.
Throughout the whole of the quadrumana the foot is pre-
hensile, and a very rigid selection must therefore have been
needed to bring about that arrangement of the bones and
muscles which has converted the thumb into a great toe, so
completely, that the power of opposability is totally lost in
every race, whatever some travellers may vaguely assert to
the contrary. It is difficult to see why the prehensile power
should have been taken away. It must certainly have been
useful in climbing, and the case of the baboons shows that it
is quite compatible with terrestrial locomotion. It may not
be compatible with perfectly easy erect locomotion ; but, then,

198 NATURAL SELECTION ux

how can we conceive that early man, as an animal, gained
anything by purely erect locomotion? Again, the hand of
man contains latent capacities and powers which are unused
by savages, and must have been even less used by palaeolithic
man and his still ruder predecessors. It has all the appear-
ance of an organ prepared for the use of civilised man, and
one which was required to render civilisation possible. Apes
make little use of their separate fingers and opposable thumbs.
They grasp objects rudely and clumsily, and look as if a much
less specialised extremity would have served their purpose as
well. I do not lay much stress on this, but, if it be proved
that some intelligent power has guided or determined the
development of man, then we may see indications of that
power in facts which, by themselves, would not serve to
prove its existence.

The Voice of Man. — The same remark will apply to another
peculiarly human character, the wonderful power, range,
flexibility, and sweetness of the musical sounds producible
by the human larynx, especially in the female sex. The
habits of savages give no indication of how this faculty could
have been developed by natural selection, because it is never
required or used by them. The singing of savages is a more
or less monotonous howling, and the females seldom sing at
all. Savages certainly never choose their wives for fine voices,-
but for rude health, and strength, and physical beauty.
Sexual selection could not therefore have developed this
wonderful power, which only comes into play among civilised
people. It seems as if the organ had been prepared in anti-
cipation of the future progress of man, since it contains latent
capacities which are useless to him in his earlier condition.
The delicate correlations of structure that give it such mar-
vellous powers could not therefore have been acquired by
means of natural selection.

The Origin of some of Man's Mental Faculties, by the pre-
servation of Useful Variations, not possible
Turning to the mind of man, we meet with many difficulties
in attempting to understand how those mental faculties,
which are especially human, could have been acquired by the
preservation of useful variations. At first sight, it would

ix LIMITS OF NATURAL SELECTION IN MAN 199

seem that such feelings as those of abstract justice and bene-
volence could never have been so acquired, because they are
incompatible with the law of the strongest, which is the
essence of natural selection. But this is, I think, an errone-
ous view, because we must look, not to individuals, but to
societies ; and justice and benevolence exercised towards mem-
bers of the same tribe would certainly tend to strengthen
that tribe and give it a superiority over another in which the
right of the strongest prevailed, and where, consequently, the
weak and the sickly were left to perish, and the few strong
ruthlessly destroyed the many who were weaker.

But there is another class of human faculties that do not
regard our fellow-men, and which cannot, therefore, be thus
accounted for. Such are the capacity to form ideal concep-
tions of space and time, of eternity and infinity — the capacity
for intense artistic feelings of pleasure, in form, colour, and
composition, and for those abstract notions of form and
number which render geometry and arithmetic possible.
How were all or any of these faculties first developed, when
they could have been of no possible use to man in his
early stages of barbarism ? How could natural selection, or
survival of the fittest in the struggle for existence, at all
favour the development of mental powers so entirely removed
from the material necessities of savage men, and which even
now, with our comparatively high civilisation, are, in their
farthest developments, in advance of the age, and appear to
have relation rather to the future of the race than to its
actual status 1 l

Difficulty as to the Origin of the Moral Sense
Exactly the same difficulty arises when we endeavour to
account for the development of the moral sense or conscience
in savage man ; for although the practice of benevolence,
honesty, or truth may have been useful to the tribe possess-
ing these virtues, that does not at all account for the peculiar
sanctity attached to actions which each tribe considers right
and moral, as contrasted with the very different feelings with
which they regard what is merely useful. The utilitarian

1 This argument is extended and some new illustrations given in Darwin-
ism, pp. 461-471.

200 NATURAL SELECTION ix

hypothesis (which is the theory of natural selection applied "to
the mind) seems inadequate to account for the development
of the moral sense. This subject has been recently much
discussed, and I will here only give one example to illustrate
my argument. The utilitarian sanction for truthfulness is by
no means very powerful or universal. Few laws enforce it.
No very severe reprobation follows untruthfulness. In all
ages and countries falsehood has been thought allowable in
love, and laudable in war; while, at the present day, it is
held to be venial by the majority of mankind in trade, com-
merce, and speculation. A certain amount of untruthfulness
is a necessary part of politeness in the East and West alike,
while even severe moralists have held a lie justifiable to elude
an enemy or prevent a crime. Such being the difficulties with
which this virtue has had to struggle, with so many excep-
tions to its practice, with so many instances in which it
brought ruin or death to its too ardent devotee, how can we
believe that considerations of utility could ever invest it with
the mysterious sanctity of the highest virtue, — could ever
induce men to value truth for its own sake, and practise it
regardless of consequences ?

Yet it is a fact that such a mystical sense of wrong does
attach to untruthfulness, not only among the higher classes of
civilised people, but among whole tribes of utter savages.
Sir Walter Elliott tells us (in his paper " On the Character-
istics of the Population of Central and Southern India,"
published in the Journal of the Ethnological Society of
London, vol. i. p. 107) that the Kurubars and Santals,
barbarous hill-tribes of Central India, are noted for veracity.
It is a common saying that "a Kurubar always speaks the
truth ; " and Major Jervis says, " the Santals are the most
truthful men I ever met with." As a remarkable instance
of this quality the following fact is given. A number of
prisoners, taken during the Santal insurrection, were allowed
to go free on parole, to work at a certain spot for wages.
After some time cholera attacked them and they were obliged
to leave, but every man of them returned and gave up his
earnings to the guard. Two hundred savages, with money in
their girdles, walked thirty miles back to prison rather than
break their word ! My own experience among savages has

ix LIMITS OF NATURAL SELECTION IN MAN 201

furnished me with similar, although lest severely tested,
instances ; and we cannot avoid asking, How is it that in
these few cases " experiences of utility " have left such an
overwhelming impression, while in so many others they have
left none ? The experiences of savage men as regards the
utility of truth must, in the long run, be pretty nearly equal.
How is it, then, that in some cases the result is a sanctity
which overrides all considerations of personal advantage, while
in others there is hardly a rudiment of such a feeling ?

The intuitional theory, which I am now advocating, ex-
plains this by the supposition that there is a feeling — a sense
of right and wrong — in our nature, antecedent to and inde-
pendent of experiences of utility. Where free play is
allowed to the relations between man and man, this feeling
attaches itself to those acts of universal utility or self-
sacrifice which are the products of our affections and sym-
pathies, and which we term moral; while it may be, and
often is, perverted, to give the same sanction to acts of narrow
and conventional utility which are really immoral, — as when
the Hindoo will tell a lie, but will sooner starve than eat
unclean food, and looks upon the marriage of adult females
as gross immorality.

The strength of the moral feeling will depend upon
individual or racial constitution, and on education and
habit ; — the acts to which its sanctions are applied will
depend upon how far the simple feelings and affections of
our nature have been modified by custom, by law, or by
religion.

It is difficult to conceive that such an intense and mystical
f eeling of right and wrong (so intense as to overcome all ideas
of personal advantage or utility), could have been developed
out of accumulated ancestral experiences of utility; and
still more difficult to understand how feelings developed by
one set of utilities could be transferred to acts of which the
utility was partial, imaginary, or altogether absent. But if a
moral sense is an essential part of our nature, it is easy to
see that its sanction may often be given to acts which are
useless or immoral ; just as the natural appetite for drink
is perverted by the drunkard into the means of his de-
struction.

202 NATURAL SELECTION

Summary of the Argument as to the Insufficiency of Natural
Selection to account for the Development of Man

Briefly to resume my argument — I have shown that the
brain of the lowest savages, and, as far as we yet know, of
the prehistoric races, is little inferior in size to that of the
highest types of man, and immensely superior to that of the
higher animals ; while it is universally admitted that quantity
of brain is one of the most important, and probably the most
essential, of the elements which determine mental power.
Yet the mental requirements of savages, and the faculties
actually exercised by them, are very little above those of
animals. The higher feelings of pure morality and refined
emotion, and the power of abstract reasoning and ideal con-
ception, are useless to them, are rarely if ever manifested, and
have no important relations to their habits, wants, desires,
or well-being. They possess a mental organ beyond their
needs. Natural selection could only have endowed savage
man with a brain a few degrees superior to that of an ape,
whereas he actually possesses one very little inferior to that
of a philosopher.

The soft, naked, sensitive skin of man, entirely free from
that hairy covering which is so universal among other mam-
malia, cannot be explained on the theory of natural selection.
The habits of savages show that they feel the want of this
covering, which is most completely absent in man exactly
where it is thickest in other animals. We have no reason
whatever to believe that it could have been hurtful or even
useless to primitive man ; and, under these circumstances, its
complete abolition, shown by its never reverting in mixed
breeds, is a demonstration of the agency of some other power
than the law of the survival of the fittest, in the development
of man from the lower animals.

Other characters show difficulties of a similar kind, though
not perhaps in an equal degree. The structure of the human
foot and hand seem unnecessarily perfect for the needs of
savage man, in whom they are as completely and as humanly
developed as in the highest races. The structure of the
human larynx, giving the power of speech and of producing
musical sounds, and especially its extreme development in

ix LIMITS OF NATURAL SELECTION IN MAN 203

the female sex, are shown to be beyond the needs of
savages, and, from their known habits, impossible to have
been acquired either by sexual selection or by survival of
the fittest.

The mind of man offers arguments in the same direction,
hardly less strong than those derived from his bodily struc-
ture. A number of his mental faculties have no relation to
his fellow-men, or to his material progress. The power of
conceiving eternity and infinity, and all those purely abstract
notions of form, number, and harmony, which play so large
a part in the life of civilised races, are entirely outside of
the world of thought of the savage, and have no influence
on his individual existence or on that of his tribe. They
could not, therefore, have been developed by any preserva-
tion of useful forms of thought ; yet we find occasional
traces of them amidst a low civilisation, and at a time when
they could have had no practical effect on the success of the
individual, the family, or the race ; and the development of
a moral sense or conscience by similar means is equally
inconceivable.

But, on the other hand, we find that every one of these
characteristics is necessary for the full development of human
nature. The rapid progress of civilisation under favourable
conditions would not be possible, were not the organ of the
mind of man prepared in advance, fully developed as regards
size, structure, and proportions, and only needing a few
generations of use and habit to co-ordinate its complex func-
tions. The naked and sensitive skin, by necessitating clothing
and houses, would lead to the more rapid development of
man's inventive and constructive faculties ; and, by leading
to a more refined feeling of personal modesty, may have
influenced, to a considerable extent, his moral nature. The
erect form of man, by freeing the hands from all locomotive
uses, has been necessary for his intellectual advancement ;
and the extreme perfection of his hands has alone rendered
possible that excellence in all the arts of civilisation which
raises him so far above the savage, and is perhaps but the
forerunner of a higher intellectual and moral advancement.
The perfection of his vocal organs has first led to the forma-
tion of articulate speech, and then to the development of

204 NATURAL SELECTION ^ ix

those exquisitely toned sounds, which are only appreciated
by the higher races, and which are probably destined for
more elevated uses and more refined enjoyment in a higher
condition than we have yet attained to. So, those faculties
which enable us to transcend time and space, and to realise
the wonderful conceptions of mathematics and philosophy, or
which give us an intense yearning for abstract truth (all of
which were occasionally manifested at such an early period
of human history as to be far in advance of any of the few
practical applications which have since grown out of them),
are evidently essential to the perfect development of man as
a spiritual being, but are utterly inconceivable as having been
produced through the action of a law which looks only, and
can look only, to the immediate material welfare of the indi-
vidual or the race.

The inference I would draw from this class of phenomena
is, that a superior intelligence has guided the development
of man in a definite direction, and for a special purpose, just
as man guides the development of many animal and vegetable
forms. The laws of evolution alone would, perhaps, never
have produced a grain so well adapted to man's use as wheat
and maize ; such fruits as the seedless banana and bread-
fruit ; or such animals as the Guernsey milch cow, or the
London dray-horse. Yet these so closely resemble the un-
aided productions of nature, that we may well imagine a
being who had mastered the laws of development of organic
forms through past ages, refusing to believe that any new
power had been concerned in their production, and scornfully
rejecting the theory (as my theory will be rejected by
many who agree with me on other points) that in these few
cases a controlling intelligence had directed the action of the
laws of variation, multiplication, and survival, for his own
purposes. We know, however, that this has been done ; and
we must therefore admit the possibility that, if we are not
the highest intelligences in the universe, some higher intelli-
gence may have directed the process by which the human
race was developed, by means of more subtle agencies than
we are acquainted with. At the same time I must confess
that this theory has the disadvantage of requiring the inter-
vention of some distinct individual intelligence, to aid in the

ix LIMITS OF NATURAL SELECTION IN MAN 205

production of what we can hardly avoid considering as the
ultimate aim and outcome of all organised existence — intel-
lectual, ever-advancing, spiritual man. It therefore implies
that the great laws which govern the material universe were
insufficient for his production, unless we consider (as we may
fairly do) that the controlling action of such higher intelli-
gences is a necessary part of those laws, just as the action of
all surrounding organisms is one of the agencies in organic
development. But even if my particular view should not be
the true one, the difficulties I have put forward remain, and,
I think, prove that some more general and more funda-
mental law underlies that of natural selection. The law of
" unconscious intelligence " pervading all organic nature, put
forth by Dr. Laycock and adopted by Mr. Murphy, is such
a law ; but to my mind it has the double disadvantage of
being both unintelligible and incapable of any kind of proof.
It is more probable that the true law lies too deep for us to
discover it ; but there seems to me to be ample indications
that such a law does exist, and is probably connected with the
absolute origin of life and organisation.1

1 Some of my critics seem quite to have misunderstood my meaning in this
part of the argument. They have accused me of unnecessarily and unphiloso-
phically appealing to "first causes" in order to get over a difficulty — of
believing that " our brains are made by God and our lungs by natural selec-
tion ;" and that, in point of fact, "man is God's domestic animal." An
eminent French critic, M. Claparede, makes me continually call in the aid of
— " une Force supfrrieure" the capital F meaning, I imagine, that this
" higher Force " is the Deity. I can only explain this misconception by the
incapacity of the modern cultivated mind to realise the existence of any
higher intelligence between itself and Deity. Angels and archangels, spirits
and demons, have been so long banished from our belief as to have become
actually unthinkable as actual existences, and nothing in modern philosophy
takes their place. Yet the grand law of "continuity," the last outcome of
modern science, which seems absolute throughout the realms of matter, force,
and mind, so far as we can explore them, cannot surely fail to be true beyond
the narrow sphere of our vision, and leave an infinite chasm between man
and the Great Mind of the universe. Such a supposition seems to me in
the highest degree improbable.

Now, in referring to the origin of man, and its possible determining
causes, I have used the words "some other power" — "some intelligent
power" — " a superior intelligence " — "a controlling intelligence," and only
in reference to the origin of universal forces and laws have I spoken of the
will or power of " one Supreme Intelligence." These are the only expres-
sions I have used in alluding to the power which I believe has acted in the
case of man, and they were purposely chosen to show that I reject the
hypothesis of " first causes " for any and every special effect in the universe,

NATURAL SELECTION

The Origin of

The question of the origin of sensation and of thought
can be but briefly discussed in this place, since it is a subject
wide enough to require a separate volume for its proper
treatment. No physiologist or philosopher has yet ventured
to propound an intelligible theory of how sensation may
possibly be a product of organisation; while many have
declared the passage from matter to mind to be inconceiv-
able. In his presidental address to the Physical Section of
the British Association at Norwich, in 1868, Professor Tyndall
expressed himself as follows : —

" The passage from the physics of the brain to the corre-
sponding facts of consciousness is unthinkable. Granted that
a definite thought and a definite molecular action in the brain
occur simultaneously, we do not possess the intellectual organ,
nor apparently any rudiment of the organ, which would
enable us to pass by a process of reasoning from the one
phenomenon to the other. They appear together, but we do
not know why. Were our minds and senses so expanded,
strengthened, and illuminated as to enable us to see and feel
the very molecules of the brain, — were we capable of following
all their motions, all their groupings, all their electric dis-
charges, if such there be, and were we intimately acquainted
with the corresponding states of thought and feeling, — we
should be as far as ever from the solution of the problem,
' How are these physical processes connected with the facts of
consciousness ? ' The chasm between the two classes of
phenomena would still remain intellectually impassable."

In his latest work (An Introduction to the Classification of
Animals), published in 1869, Professor Huxley unhesitatingly

except in the same sense that the action of man or of any other intelligent
being is a first cause. In using such terms I wished to show plainly that I
contemplated the possibility that the development of the essentiaUy human
portions of man's structure and intellect may have been determined by the
directing influence of some higher intelligent beings, acting through natural
and universal laws. A belief of this nature may or may not have a founda-
tion, but it is an intelligible theory, and is not, in its nature, incapable of
proof ; and it rests on facts and arguments of an exactly similar kind to
those which would enable a sufficiently powerful intellect to deduce,
from the existence on the earth of cultivated plants and domestic animals,
the presence of some intelligent being of a higher nature than themselves.

ix LIMITS OF NATURAL SELECTION IN MAN 207

adopts the " well founded doctrine that life is the cause and
not the consequence of organisation." In his celebrated
article " On the Physical Basis of Life," however, he maintains
that life is a property of protoplasm, and that protoplasm
owes its properties to the nature and disposition of its
molecules. Hence he terms it "the matter of life," and
believes that all the physical properties of organised beings
are due to the physical properties of protoplasm. So far we
might, perhaps, follow him, but he does not stop here. He
proceeds to bridge over that chasm which Professor Tyndall
has declared to be " intellectually impassable," and, by means
which he states to be logical, arrives at the conclusion that
our "thoughts are the expression of molecular changes in that
matter of life which is the source of our other vital phenomena."
Not having been able to find any clue in Professor Huxley's
writings to the steps by which he passes from those vital
phenomena, which consists only, in their last analysis, of
movements of particles of matter, to those other phenomena
which we term thought, sensation, or consciousness, but
knowing that so positive an expression of opinion from him
will have great weight with many persons, I shall endeavour
to show, with as much brevity as is compatible with clearness,
that this theory is not only incapable of proof, but is also, as
it appears to me, inconsistent with accurate conceptions of
molecular physics. To do this, and in order further to
develop my views, I shall have to give a brief sketch of the
most recent speculations and discoveries as to the ultimate
nature and constitution of matter.

The Nature of Matter

It has been long seen by the deepest thinkers on the
subject, that atoms, — considered as minute solid bodies from
which emanate the attractive and repulsive forces which give
what we term matter its properties, — could serve no purpose
whatever ; since it is universally admitted that the supposed
atoms never touch each other, and it cannot be conceived that
these homogeneous, indivisible, solid units are themselves the
ultimate cause of the forces that emanate from their centres.
As, therefore, none of the properties of matter can be due to
the atoms themselves, but only to the forces which emanate

NATURAL SELECTION

from the points in space indicated by the atomic centres, it
is logical continually to diminish their size till they vanish,
leaving only localised centres of force to represent them. Of
the various attempts that have been made to show how the
properties of matter may be due to such modified atoms
(considered as mere centres of force), the most successful,
because the simplest and the most logical, is that of Mr.
Bayma, who, in his Molecular Mechanics, has demonstrated
how, from the simple assumption of such centres having
attractive and repulsive forces (both varying according to
the same law of the inverse squares as gravitation), and by
grouping them in symmetrical figures, consisting of a repulsive
centre, an attractive nucleus, and one or more repulsive
envelopes, we may explain all the general properties of matter ;
and, by more and more complex arrangements, even the
special chemical, electrical, and magnetic properties of special
forms of matter.1 Each chemical element will thus consist of
a molecule formed of simple atoms (or as Mr. Bayma terms
them, to avoid confusion, " material elements ") in greater or
less number and of more or less complex arrangement ; which
molecule is in stable equilibrium, but liable to be changed in
form by the attractive or repulsive influences of differently
constituted molecules, constituting the phenomena of chemical
combination, and resulting in new forms of molecule of greater
complexity and more or less stability.

Those organic compounds of which organised beings are
built up consist, as is well known, of matter of an extreme
complexity and great instability ; whence result the changes
of form to which it is continually subject. This view en-
ables us to comprehend the possibility of the phenomena of
vegetative life being due to an almost infinite complexity of

1 Mr. Bayma's work, entitled The Elements of Molecular Mechanics, was
published in 1866, and has received less attention than it deserves. It is
characterised by great lucidity, by logical arrangement, and by comparatively
simple geometrical and algebraical demonstrations, so that it may be under-
stood and appreciated with a very moderate knowledge of mathematics. It
consists of a series of Propositions, deduced from the known properties of
matter ; from these are derived a number of Theorems, by whose help the
more complicated Problems are solved. Nothing is taken for granted through-
out the work, and the only valid mode of escaping from its conclusions is, by
either disproving the fundamental Propositions, or by detecting fallacies in the
subsequent reasoning.

ix LIMITS OF NATURAL SELECTION IN MAN 209

molecular combinations, subject to definite changes under the
stimuli of heat, moisture, light, electricity, and probably some
unknown forces. But this greater and greater complexity,
even if carried to an infinite extent, cannot, of itself, have the
slightest tendency to originate consciousness in such molecules
or groups of molecules. If a material element, or a combina-
tion of a thousand material elements in a molecule, are alike
unconscious, it is impossible for us to believe that the mere
addition of one, two, or a thousand other material elements to
form a more complex molecule, could in any way tend to
produce a self-conscious existence. The things are radically
unlike, exclusive, and incommensurable. To say that mind is a
product or function of protoplasm, or of its molecular changes,
is to use words to which we can attach no clear conception ;
and those who argue thus should put forth a precise definition
of matter with clearly enunciated properties, and show that
the necessary result of a certain complex arrangement of the
elements or atoms of that matter will be the production of self-
consciousness. There is no escape from this dilemma, — either
all matter is conscious, or consciousness is, or pertains to, some-
thing distinct from matter, and in the latter case its presence
in material forms is a proof of the existence of conscious beings,
outside of, and independent of, what we term matter.1

1 A friend has suggested that I have not here explained myself sufficiently,
and objects that life does not exist in matter any more than consciousness,
and if the one can be produced by the laws of matter, why may not the other ?
I reply that there is a radical difference between the two. Organic or
vegetative life consists essentially in chemical transformations and molecular
motions, occurring under certain conditions and in a certain order. The
matter and the forces which act upon it are for the most part known ; and
if there are any forces engaged in the manifestation of vegetative life yet
undiscovered (which is a moot question), we can conceive them as analogous
to such forces as heat, electricity, or chemical affinity, with which we are
already acquainted. We can thus clearly conceive of the transition from dead
matter to living matter. A complex mass which suffers decomposition or
decay is dead, but if this mass has the power of attracting to itself from the
surrounding medium, matter like that of which it is composed, we have the
lirst rudiment of vegetative life. If the mass can do this for a considerable
time, and if its absorption of new matter more than replaces that lost by
decomposition, and if it is of such a nature as to resist the mechanical 01
chemical forces to which it is usually exposed, and to retain a tolerably
constant form, we term it a living organism. We can conceive an organism t<
be so constituted, and we can further conceive that any fragments, which may
be accidentally broken from it, or which may fall away when its bulk hs
become too great for the cohesion of all its parts, may begin to increase anew
P

210 NATURAL SELECTION

Matter is Force

The foregoing considerations lead us to the very
important conclusion that matter is essentially force, and
nothing but force; that matter, as popularly understood,
does not exist, and is, in fact, philosophically inconceivable.
When we touch matter, we only really experience sensations
of resistance, implying repulsive force ; and no other sense
can give us such apparently solid proofs of the reality of
matter as touch does. This conclusion, if kept constantly
present in the mind, will be found to have a most important
bearing on almost every high scientific and philosophical
problem, and especially on such as relate to our own conscious
existence.

and run the same course as the parent mass. This is growth and reproduction
in their simplest forms ; and from such a simple beginning it is possible to
conceive a series of slight modifications of composition, and of internal and
external forces, which should ultimately lead to the development of more
complex organisms. The LIFE of such an organism may, perhaps, be nothing
added to it, but merely the name we give to the result of a balance of internal
and external forces in maintaining the permanence of the form and structure of
the individual. The simplest conceivable form of such life would be the dew-
drop, which owes its existence to the balance between the condensation of
aqueous vapour in the atmosphere and the evaporation of its substance. If
either is in excess, it soon ceases to maintain an individual existence. I do
not maintain that vegetative life is wholly due to such a complex balance of
forces, but only that it is conceivable as such.

With CONSCIOUSNESS the case is very different. Its phenomena are not
comparable with those of any kind of matter subjected to any of the known
or conceivable forces of nature ; and we cannot conceive a gradual transition
from absolute unconsciousness to consciousness, from an unsentient organism
to a sentient being. The merest rudiment of sensation or self-consciousness
is infinitely removed from absolutely non- sentient or unconscious matter.
We can conceive of no physical addition to, or modification of, an unconscious
mass which should create consciousness ; no step in the series of changes
organised matter may undergo, which should bring in sensation where there
was no sensation or power of sensation at the preceding step. It is because
the things are utterly incomparable and incommensurable that we can only
conceive of sensation coming to matter from without, while life may be con-
ceived as merely a specific combination and co-ordination of the matter and
the forces that compose the universe, and with which we are separately
acquainted. We may admit with Professor Huxley that protoplasm is the
"matter of life" and the cause of organisation, but we cannot admit or con-
ceive that protoplasm is the primary source of sensation and consciousness, or
that it can ever of itself become conscious in the same way as we may perhaps
conceive that it may become alive.

LIMITS OF NATURAL SELECTION IN MAN 211

All Force is probably Will-Farce,

If we are satisfied that force or forces are all that exist
in the material universe, we are next led to inquire
what is force ? We are acquainted with two radically
distinct or apparently distinct kinds of force — the first
consists of the primary forces of nature, such as gravitation,
cohesion, repulsion, heat, electricity, etc. ; the second is
our own will -force. Many persons will at once deny that
the latter exists. It will be said that it is a mere trans-
formation of the primary forces before alluded to ; that the
correlation of forces includes those of animal life, and that
will itself is but the result of molecular change in the brain.
I think, however, that it can be shown that this latter asser-
tion has neither been proved, nor even been proved to be
possible ; and that in making it, a great leap in the dark has
been taken from the known to the unknown. It may be at
once admitted that the muscular force of animals and men is
merely the transformed energy derived from the primary
forces of nature. So much has been, if not rigidly proved,
yet rendered highly probable, and it is in perfect accordance
with all our knowledge of natural forces and natural laws.
But it cannot be contended that the physiological balance-
sheet has ever been so accurately struck, that we are entitled
to say, not one-thousandth part of a grain more of force has
been exerted by any organised body, or in any part of it, than
has been derived from the known primary forces of the
material world. If that were so, it would absolutely negative
the existence of will ; for if will is anything, it is a power that
directs the action of the forces stored up in the body, and it is
not conceivable that this direction can take place, without the
exercise of some force in some part of the organism. How-
ever delicately a machine may be constructed, with the most
exquisitely contrived detents to release a weight or spring by
the exertion of the smallest possible amount of force, some
external force will always be required ; so, in the animal
machine, however minute may be the changes required in
the cells or fibres of the brain, to set in motion the nerve
currents which loosen or excite the pent-up forces of certain
muscles, some force must be required to effect those changes.

212 NATURAL SELECTION ix

If it is said, "those changes are automatic, and are set in
motion by external causes," then one essential part of our
consciousness, a certain amount of freedom in willing, is
annihilated ; and it is inconceivable how or why there should
have arisen any consciousness or any apparent will, in such
purely automatic organisms. If this were so, our apparent
WILL would be a delusion, and Professor Huxley's belief
" that our volition counts for something as a condition of the
course of events," would be fallacious, since our volition would
then be but one link in the chain of events, counting for
neither more nor less than any other link whatever.

If, therefore, we have traced one force, however minute,
to an origin in our own WILL, while we have no knowledge of
any other primary cause of force, it does not seem an improb-
able conclusion that all force may be will-force ; and thus,
that the whole universe is not merely dependent on, but actu-
ally is, the WILL of higher intelligences or of one Supreme In-
telligence. It has been often said that the true poet is a seer ;
and in the noble verse of an American poetess we find ex-
pressed what may prove to be the highest fact of science, the
noblest truth of philosophy :

God of the Granite and the Rose !

Soul of the Sparrow and the Bee !
The mighty tide of Being flows

Through countless channels, Lord, from Thee.
It leaps to life in grass and flowers,

Through every grade of being runs,
While from Creation's radiant towers

Its glory flames in Stars and Suns.

Conclusion

These speculations are usually held to be far beyond the
bounds of science ; but they appear to me to be more legiti-
mate deductions from the facts of science than those which
consist in reducing the whole universe, not merely to matter,
but to matter conceived and defined so as to be philosophically
inconceivable. It is surely a great step in advance, to get
rid of the notion that matter is a thing of itself, which can
exist per se, and must have been eternal, since it is supposed
to be indestructible and uncreated, — that force, or the forces

ix LIMITS OF NATURAL SELECTION IN MAN 218

of nature, are another thing, given or added to matter, or else
its necessary properties, — and that mind is yet another thing,
either a product of this matter and its supposed inherent
forces, or distinct from and co- existent with it; — and to be
able to substitute for this complicated theory, which leads to
endless dilemmas and contradictions, the far simpler and
more consistent belief, that matter, as an entity distinct from
force, does not exist ; and that FORCE is a product of MIND.
Philosophy had long demonstrated our incapacity to prove
the existence of matter, as usually conceived ; while it ad-
mitted the demonstration to each of us of our own self-con-
scious, spiritual existence. Science has now worked its way
up to the same result, and this agreement between them
should give us some confidence in their combined teaching.

The view we have now arrived at seems to me more grand
and sublime, as well as far simpler, than any other. It ex-
hibits the universe as a universe of intelligence and will-
power ; and by enabling us to rid ourselves of the impossi-
bility of thinking of mind, but as connected with our old
notions of matter, opens up infinite possibilities of existence,
connected with infinitely varied manifestations of force, totally
distinct from, yet as real as, what we term matter.

The grand law of continuity which we see pervading our
universe would lead us to infer infinite gradations of existence,
and to people all space with intelligence and will-power ; and,
if so, we shall have no difficulty in believing that for so noble
a purpose as the progressive development of higher and higher
intelligences, those primal and general will-forces, which have
sufficed for the production of the lower animals, should have
been guided into new channels and made to converge in
definite directions. And if, as seems to me probable, this
has been done, I cannot admit that it in any degree affects
the truth or generality of Mr. Darwin's great discovery. It
merely shows that the laws of organic development have
been occasionally used for a special end, just as man uses
them for his special ends ; and I do not see that the law
of natural selection can be said to be disproved, if it can
be shown that man does not owe his entire physical and
mental development to its unaided action, any more than
it is disproved by the existence of the poodle or the pouter

214 NATURAL SELECTION ix

pigeon, the production of which are equally beyond its
undirected power.

The objections which in this essay I have taken to the
view that the same law which appears to have sufficed for
the development of animals has been alone the cause of man's
superior physical and mental nature, will, I have no doubt,
be overruled and explained away. But I venture to think
they will nevertheless maintain their ground, and that they
can only be met by the discovery of new facts or new laws,
of a nature very different from any yet known to us. I can
only hope that my treatment of the subject, though neces-
sarily very meagre, has been clear and intelligible ; and that
it may prove suggestive both to the opponents and to the
upholders of the theory of natural selection.

TROPICAL NATURE AND OTHER ESSAYS

THE CLIMATE AND PHYSICAL ASPECTS OF THE EQUATORIAL
ZONE

The three Climatal Zones of the Earth— Temperature of the Equatorial
Zone — Causes of the Uniform High Temperature near the Equator —
Influence of the Heat of the Soil — Influence of the Aqueous Vapour
of the Atmosphere — Influence of Winds on the Temperature of the
Equator — Heat due to the Condensation of Atmospheric Vapour —
General features of the Equatorial Climate— Uniformity of the Equa-
torial Climate in all parts of the Globe — Effects of Vegetation on
Climate— Short Twilight of the Equatorial Zone— The aspect of the
Equatorial Heavens— Intensity of Meteorological Phenomena at the
Equator — Concluding Remarks.

IT is difficult for an inhabitant of our temperate land to
realise either the sudden and violent contrasts of the arctic
seasons or the wonderful uniformity of the equatorial climate.
The lengthening or the shortening days, the ever- changing
tints of spring, summer, and autumn, succeeded by the leafless
boughs of winter, are constantly recurring phenomena which
represent to us the established course of nature. At the
equator none of these changes occur ; there is a perpetual
equinox and a perpetual summer, and were it not for variations
in the quantity of rain, in the direction and strength of the
winds, and in the amount of sunshine, accompanied by corre-
sponding slight changes in the development of vegetable and
animal life, the monotony of nature would be extreme.

In the present chapter it is proposed to describe the chief
peculiarities which distinguish the equatorial from the tem-
perate climate, and to explain the causes of the difference
between them, — causes which are by no means of so simple a
nature as are usually imagined.

218 TROPICAL NATURE

The Three Climatal Zones of the Earth

The three great divisions of the earth — the tropical, the
temperate, and the frigid zones — may be briefly defined as
the regions of uniform, of variable, and of extreme physical
conditions respectively. They are primarily determined by
the circumstance of the earth's axis not being perpendicular
to the plane in which it moves round the sun ; whence it
follows that during one half of its revolution the north pole,
and during the other half the south pole, is turned at a con-
siderable angle towards the source of light and heat. This
inclination of the axis on which the earth rotates is usually
defined by the inclination of the equator to the plane of the
orbit, termed the obliquity of the ecliptic. The amount of
this obliquity is 23£ degrees, and this measures the extent on
each side of the equator of what are called the tropics, because
within these limits the sun becomes vertical at noon twice a
year, and at the extreme limit once a year, while beyond this
distance it is never vertical. It will be evident, however,
from the nature of the case, that the two lines which mark
the limits of the geographical " tropics " will not define any
abrupt change of climate or physical conditions, such as
characterise the tropical and temperate zones in their full
development. There will be a gradual transition from one to
the other, and in order to study them separately and contrast
their special features we must only take into account the
portion of each in which these are most fully exhibited. For
the temperate zone we may take all countries situated be-
tween 35° and 60° of latitude, which in Europe will include
every place between Christiana and Algiers, the districts
farther south forming a transitional belt in which temperate
and tropical features are combined. In order to study the
special features of tropical nature, on the other hand, it will
be advisable to confine our attention mainly to that portion
of the globe which extends for about twelve degrees on each
side of the equator, in which all the chief tropical phenomena
dependent on astronomical causes are most fully manifested,
and which we may distinguish as the "equatorial zone." In
the debatable ground between these two well-contrasted belts
local causes have a preponderating influence ; and it would

I CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 219

not be difficult to point out localities within the temperate
zone of our maps, which exhibit all the chief characteristics of
tropical nature to a greater degree than other localities which
are, as regards geographical position, tropical.

Temperature of the Equatorial Zone

The most characteristic, as it is the most important feature
in the physical conditions of the great equatorial zone,
is the wonderful uniformity of its temperature, alike
throughout the changes of day and night, and from one
part of the year to another. As a general rule, the
greatest heat of the day does not exceed 90° or 91° Fahr.,
while it seldom falls during the night below 74° Fahr. It
has been found by hourly observations carried on for three
years at the meteorological observatory established by the
Dutch government at Batavia, that the extreme range of
temperature in that period was only 27° Fahr., the maximum
being 95° and the minimum 68°. But this is, of course, very
much beyond the usual daily range of the thermometer, which
is, on the average, only a little more than 11° Fahr. ; being
12 '6° in September, when it is greatest, and only 8'1° in
January, when it is least.

Batavia, being situated between six and seven degrees
south of the equator, may be taken as affording a fair example
of the climate of the equatorial zone ; though, being in an
island, it is somewhat less extreme than many continental
localities. Observations made at Para, which is on the South
American Continent, and close to the equator, agree, however,
very closely with those at Batavia ; but at the latter place all
the observations were made with extreme care and with the
best instruments, and are therefore preferred as being
thoroughly trustworthy.1 The accompanying diagram, show-
ing by curves the monthly means of the highest and lowest
daily temperatures at Batavia and London, is very instructive ;
more especially when we consider that the maximum of tem-
perature is by no means remarkably different in the two

1 " Observations made at the Magnetical and Meteorological Observatory
at Batavia. Published by order of the Government of Netherlands, India.
Vol. I. Meteorological, from Jan. 1866 to Dec. 1868 ; and Magnetical, from
July 1867 to June 1870. By Dr. P. A. Bergsma, Batavia, 1871." This
fine work is entirely in English.

TROPICAL NATURE

Monthly 'Mean Ternpercdnre af> Satavia^ &Iondon.

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i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 221

places, 90° Fahr. being sometimes reached with us and not
being often very much exceeded at Batavia.

Causes of the uniform High Temperature near the Eguatw
It is popularly supposed that the uniform high temperature
of the tropics is sufficiently explained by the greater altitude,
and therefore greater heating-power of the midday sun ; but
a little consideration will show that this alone by no means
accounts for the phenomenon. The island of Java is situated
in from six and a half to eight and a half degrees of south
latitude, and in the month of June the sun's altitude at noon
will not be more than from 58° to 60°. In the same month
at London, which is fifty -one and a half degrees of north
latitude, the sun's noonday altitude is 62°. But besides this
difference of altitude in favour of London there is a still more
important difference, for in Java the day is only about eleven
and a half hours long in the month of June, while at London
it is sixteen hours long, so that the total amount of sun-heat
received by the earth must be then very much greater at
London than at Batavia. Yet at the former place the mean
temperature of the day and night is under 60° Fahr., while
in the latter place it is 80° Fahr., the daily maximum being
on the average in the one case about 68° and in the other
about 89°.

Neither does the temperature at the same place depend
upon the height of the sun at noon ; for at Batavia it is nearly
vertical during October and February, but these are far from
being the hottest months, which are May, June, and Sep-
tember, while December, January, and February are the
coldest months, although then the sun attains nearly its
greatest altitude. It is evident, therefore, that a difference of
30° in the altitude of the sun at noon, at different times of
the year, has no apparent influence in raising the temperature
of a place near the equator, and hence we conclude that other
agencies are at work which often completely neutralise the
effect which increased altitude must undoubtedly exert.

There is another important difference between the tem-
perate and tropical zones, in the direct heating effect of the
sun's rays independently of altitude. In England the noon-
day sun in the month of June rarely inconveniences us or

222 TROPICAL NATURE

produces any burning of the skin, while in the tropics at
almost any hour of the day, and when the sun has an eleva-
tion of only 40° or 50°, exposure to it for a few minutes will
scorch a European so that the skin turns red, becomes painful,
and often blisters or peels off. Almost every visitor to the
tropics suffers from incautious exposure of the neck, the leg,
or some other part of the body to the sun's rays, which there
possess a power as new as it is at first sight inexplicable, for
it is not accompanied by any extraordinary increase in the
temperature of the air.

These very different effects, produced by the same amount
of sun-heat poured upon the earth in different latitudes, is
due to a combination of causes. The most important of these
are, probably, — the constant high temperature of the soil and
of the surface-waters of the ocean, — the great amount of
aqueous vapour in the atmosphere, — the great extent of the
intertropical regions which cause the winds that reach the
equatorial zone to be always warm, — and the latent heat
given out during the formation of rain and dew. We will
briefly consider the manner in which each of these causes
contributes to the high degree and great uniformity of the
equatorial temperature.

Influence of the Heat of the Soil

It is well known that at a very moderate depth the soil
maintains a uniform temperature during the twenty -four
hours, while at a greater depth even the annual inequalities
disappear, and a uniform temperature, which is almost exactly
the mean temperature of the air in the same locality, is con-
stantly maintained throughout the year. The depth at which
this uniform temperature is reached is greater as the annual
range of temperature is greater, so that it is least near the
equator, and greatest in localities near the arctic circle, where
the greatest difference between summer and winter tempera-
ture prevails. In the vicinity of the equator, where the
annual range of the thermometer is so small as we have seen
it to be at Batavia, the mean temperature of about 80° Fahr.
is reached at a depth of four or five feet. The surplus heat
received during the day is therefore conducted downwards
very slowly, the surface soil becomes greatly super -heated,

i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 223

and a large portion of this heat is given out at night and thus
keeps up the high temperature of the air when the sun has
ceased to warm the earth. In the temperate zones, on the
other hand, the stratum of uniform earth -temperature lies
very deep. At Geneva it is not less than from thirty to
forty feet, and with us it is probably fifty or sixty feet, and
the temperature found there is nearly forty degrees lower
than at the equator. This great body of cool earth absorbs
a large portion of the surface heat during the summer, and
conducts it downwards with comparative rapidity, and it is
only late in the year (in July and August), when the upper
layers of the soil have accumulated a surplus store of solar
heat, that a sufficient quantity is radiated at night to keep up
a rather high temperature in the absence of the sun. At the
equator, on the other hand, this radiation is always going on,
and earth-heat is one of the most important of the agencies
which tend to equalise the equatorial climate.

Influence of the Aqueous Vapour of the Atmosphere
The aqueous vapour which is always present in consider-
able quantities in the atmosphere, exhibits a singular and
very important relation to solar and terrestrial heat. The
rays of the sun pass through it unobstructed to the earth ;
but the warmth given off by the heated earth is very largely
absorbed by it, thus raising the temperature of the air ; and
as it is the lower strata of air which contain most vapour,
these act as a blanket to the earth, preventing it from losing
heat at night by radiation into spec. During a large part
of the year the air in the equatorial zone is nearly saturated
with vapour, so that, notwithstanding the heat, salt and
sugar become liquid, and all articles of iron get thickly coated
with rust. Complete saturation being represented by 100,
the daily average of greatest humidity at Batavia reaches 96
in January and 92 in December. In January, which is the
dampest month, the range of humidity is small (77 to 96),
and at this time the range of temperature is also least ; while
in September, with a greater daily range of humidity (62 to
92) the range of temperature is the greatest, and the lowest
temperatures are recorded in this and the preceding month.
It is a curious fact that in many parts of England the degree

224 TROPICAL NATURE

of humidity, as measured by the comparative saturation of the
air, is as great as that of Batavia or even greater. A register
kept at Clifton during the years 1853-1862 shows a mean
humidity in January of 90, while the highest monthly mean
for the four years at Batavia was 88 ; and while the lowest
of the monthly means at Clifton was 79 '1, the lowest at
Batavia was 78 '9. These figures, however, represent an
immense difference in the quantity of vapour in every cubic
foot of air. In January at Clifton, with a temperature of 35°
to 40° Fahr., there would be only about 4 to 4| grains of
vapour per cubic foot of air, while at Batavia, with a tem-
perature from 80° to 90° Fahr., there would be about 20
grains in the same quantity of air. The most important fact,
however, is, that the capacity of air for holding vapour in
suspension increases more rapidly than temperature increases,
so that a fall of ten degrees at 50° Fahr. will lead to the con-
densation of about 1^ grain of vapour per cubic foot, while a
similar fall at 90° Fahr. will set free 6 £ grains. We can thus
understand how it is that the very moderate fall of the ther-
mometer during a tropical night causes heavier dews and a
greater amount of sensible moisture than are ever experienced
during much greater variations of temperature in the tem-
perate zone. It is this large quantity of vapour in the
equatorial atmosphere that keeps up a genial warmth
throughout the night by preventing the radiation into space
of the heat absorbed by the surface soil during the day.
That this is really the case is strikingly proved by what occurs
in the plains of Northern India, where the daily maximum of
heat is far beyond anything experienced near the equator,
yet, owing to the extreme dryness of the atmosphere, the clear
nights are very cold, radiation being sometimes so rapid that
water placed in shallow pans becomes frozen over.

As the heated earth, and everything upon its surface, does
not cool so fast when surrounded by moist as by dry air, it
follows that even if the quantity and intensity of the solar
rays falling upon two given portions of the earth's surface are
exactly equal, yet the sensible and effective heat produced in
the two localities may be very different according as the
atmosphere contains much or little vapour. In the one case
the heat is absorbed more rapidly than it can escape by radia-

i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 226

tion ; in the other case it radiates away into space, and is lost,
more rapidly than it is being absorbed. In both cases an
equilibrium will be arrived at, but in the one case the result-
ing mean temperature will be much higher than in the other.
Thus we can understand the burning effects of the sun's rays
in the tropics, since it results from the inability of the skin
to part with the heat, either by radiation, evaporation, or
absorption, as fast as it is received, and thus a temperature is
quickly reached which disorganises the delicate structures of
the epidermis.

Influence of Winds on the Temperature of the Equator
The distance from the northern to the southern tropics
being considerably more than three thousand miles, and the
area of the intertropical zone more than one-third the whole
area of the globe, it becomes hardly possible for any currents
of air to reach the equatorial belt without being previously
warmed by contact with the earth or ocean, or by mixture
with the heated surface-air which is found in all intertropical
and sub-tropical lands. This warming of the air is rendered
more certain and more effective by the circumstance that all
currents of air coming from the north or south have their
direction changed owing to the increasing rapidity of the
earth's rotational velocity, so that they reach the equator as
easterly winds, and thus pass obliquely over a great extent of
the heated surface of the globe. The causes that produce the
westerly monsoons act in a similar manner, so that on the
equator direct north or south winds, except as local land and
sea-breezes, are almost unknown. The Batavia observations
show that for ten months in the year the average direction
of the wind varies only between 5° and 30° from due east or
west, and these are also the strongest winds. In the two
months — March and October — when the winds are northerly,
they are very light, and are probably in great part local
sea-breezes, which, from the position of Batavia, must
come from the north over about two thousand miles of warm
land and sea. As a rule, therefore, every current of air at
or near the equator has passed obliquely over an immense
extent of tropical surface and is thus necessarily a warm
wind.

Q

TROPICAL NATURE

In the north temperate zone, on the other hand, the winds
are always cool, and often of very low temperature even in
the height of summer, due probably to their coming from
colder northern regions as easterly winds, or from the upper
parts of the atmosphere as westerly winds ; and this constant
supply of cool air, combined with quick radiation through a
dryer atmosphere, carries off the solar heat so rapidly that an
equilibrium is only reached at a comparatively low tempera-
ture. In the equatorial zone, on the contrary, the heat
accumulates, on account of the absence of any medium of
sufficiently low temperature to carry it off rapidly, and it thus
soon reaches a point high enough to produce those scorching
effects which are so puzzling when the altitude of the sun or
the indications of the thermometer are alone considered.
Whenever, as is sometimes the case, exceptional cold occurs
near the equator, it can almost always be traced to the in-
fluence of currents of air of unusually low temperature. Thus
in July near the Aru islands, the writer experienced a strong
south-east wind which almost neutralised the usual effects of
tropical heat, although the weather was bright and sunny.
But the wind, coming direct from the southern ocean during
its winter without acquiring heat by passing over land, was
necessarily of a low temperature. Again, Mr. Bates informs
us that in the Upper Amazon in the month of May there is a
regularly recurring south wind which produces a remarkable
lowering of the usual equatorial temperature. But owing to
the increased velocity of the earth's surface at the equator a
south wind there must have been a south-west wind at its
origin, and this would bring it directly from the high chain
of the Peruvian Andes during the winter of the southern
hemisphere. It is therefore probably a cold mountain wind,
and blowing as it does over a continuous forest, it has been
unable to acquire the usual tropical warmth.

The cause of the striking contrast between the climates of
equatorial and temperate lands at times when both are
receiving an approximately equal amount of solar heat may
perhaps be made clearer by an illustration. Let us suppose
there to be two reservoirs of water, each supplied by a pipe
which pours into it a thousand gallons a day, but which runs
only during the daytime, being cut off at night. The reser-

i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 227

voirs are both leaky, but while the one loses at the rate of.
nine hundred gallons in the twenty-four hours, the other loses
at the rate of eleven hundred gallons in the same time, sup-
posing that both are kept exactly half full and thus subjected
to the same uniform water-pressure. If now both are left to
be supplied by the above-mentioned pipes the result will be,
that in the one which loses by leakage less than it receives
the water will rise day by day till the increased pressure
causes the leakage to increase to such an extent as exactly to
balance the supply ; while in the other the water will sink till
the decreasing pressure causes the leakage to decrease till it
also just balances the supply, when both will remain stationary,
the one at a high the other at a low average level, each rising
during the day and sinking again at night. Just the same
thing occurs with that great heat-reservoir the earth, whose
actual temperature at any spot will depend, not alone upon
the quantity of heat it receives, but on the balance between
its constantly varying waste and supply. We can thus under-
stand how it is that, although in the months of June and
July, Scotland in latitude 57° north receives as much sun-
heat as Angola or Timor in latitude 10° south, and for a much
greater number of hours daily, yet in the latter countries
the mean temperature will be about 80° Fahr., with a daily
maximum of 90° to 95°, while in the former the mean will be
about 60° Fahr., with a daily maximum of 70° or 75° ; and,
while in Scotland exposure to the full noon-day sun produces
no unpleasant heat-sensations, a similar exposure in Timor at
any time between 9 A.M. and 3 P.M. would blister the skin in a
few minutes almost as effectually as the application of scalding
water.

Heat due to the Condensation of AtmospJieric Vapour

Another cause which tends to keep up a uniform high tem-
perature in the equatorial, as compared with the variable
temperatures of the extra-tropical zones, is the large amount
of heat liberated during the condensation of the aqueous
vapour of the atmosphere in the form of rain and dew.
Owing to the frequent near approach of the equatorial atmos-
phere to the saturation point, and the great amount of vapour
its high temperature enables it to hold in suspension, a very

228

TROPICAL NATURE

slight fall of the thermometer is accompanied by the conden-
sation of a large absolute quantity of atmospheric vapour, so

Monihfy Ucdnfall ccb London

that copious dews and heavy showers of rain are produced at
comparatively high temperatures, and even at the sea level.

i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 229

The drops of rain rapidly increase in size while falling through
the saturated atmosphere ; and during this process as well as
by the formation of dew, the heat which retained the water
in the gaseous form, and was insensible while doing so, is
liberated, and thus helps to keep up the high temperature of
the air. This production of heat is almost always going on.
In fine weather the nights are always dewy, and the diagram
on the preceding page, showing the mean monthly rainfall at
Batavia and Greenwich, proves that this source of increased
temperature is present during every month in the year, since
the lowest monthly fall at the former place is almost equal to
the highest monthly fall at the latter.

It may perhaps be objected that evaporation must absorb
as much heat as is afterwards liberated by condensation, and
this is true ; but as evaporation and condensation occur usually
at different times and in different places, the equalising effect
is still very important. Evaporation' occurs chiefly during
the hottest sunshine, when it tends to moderate the extreme
heat, while condensation takes place chiefly at night in the
form of dew and rain, when the liberated heat helps to make
up for the loss of the direct rays of the sun. Again the most
copious condensation both of dew and rain is greatly influ-
enced by vegetation and especially by forests, and also by the
presence of hills and mountains, and is therefore greater on
land than on the ocean, while evaporation is much greater on
the ocean, both on account of the less amount of cloudy
weather and because the air is more constantly in motion.
This is particularly the case throughout that large portion of
the tropical and subtropical zones where the trade-winds con-
stantly blow, as the evaporation must there be enormous
while the quantity of rain is very small. It follows, then,
that on the equatorial land-surface there will be a consider-
able balance of condensation over evaporation, which must
tend to the general raising of the temperature, and, owing to
the condensation being principally at night, not less power-
fully to its equalisation.

General Features of the Equatorial Climate

The various causes now enumerated are sufficient to enable
us to understand how the great characteristic features of the

TROPICAL NATURE

climate of the equatorial zone are brought about, how it is
that so high a temperature is maintained during the absence
of the sun at night, and why so little effect is produced by
the sun's varying altitude during its passage from the northern
to the southern tropic. In this favoured zone the heat is
never oppressive, as it so often becomes on the borders of the
tropics; and the large absolute amount of moisture always
present in the air is almost as congenial to the health of man
as it is favourable to the growth and development of vegeta-
tion.1 Again, the lowering of the temperature at night is so
regular and yet so strictly limited in amount, that, although
never cold enough to be unpleasant, the nights are never so
oppressively hot as to prevent sleep. During the wettest
months of the year, it is rare to have many days in succession
without some hours of sunshine, while even in the driest
months there are occasional showers to cool and refresh the
overheated earth. As' a result of this condition of the earth
and atmosphere, there is no check to vegetation, and little if
any demarcation of the seasons. Plants are all evergreen;
flowers and fruits, although more abundant at certain seasons,
are never altogether absent; while many annual food-plants
as well as some fruit -trees produce two crops a year. In
other cases, more than one complete year is required to
mature the large and massive fruits, so that it is not uncom-
mon for fruit to be ripe at the same time that the tree is
covered with flowers in preparation for the succeeding crop.
This is the case with the Brazil nut tree in the forests of the
Amazon, and with many other tropical as with a few tem-
perate fruits.

Uniformity of the Equatorial Climate in all Parts of the Globe
The description of the climatal phenomena of the equatorial
zone here given has been in great part drawn from long
personal experience in South America and in the Malay
Archipelago. Over a large portion of these countries the
same general features prevail, only modified by varying local

1 Where the inhabitants adapt their mode of life to the peculiarities of
the climate, as is the case with the Dutch in the Malay Archipelago, they
enjoy as robust health as in Europe both in the case of persons born in
Europe and of those who for generations have lived under a vertical sun.

I CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 231

conditions. Whether we are at Singapore or Batavia, in the
Moluccas or New Guinea, at Para, at the sources of the
Rio Negro, or on the Upper Amazon, the equatorial climate
is essentially the same, and we have no reason to believe that
it materially differs in Guinea or the Congo. In certain
localities, however, a more contrasted wet and dry season
prevails, with a somewhat greater range of the thermometer.
This is generally associated with a sandy soil, and a less dense
forest, or with an open and more cultivated country. The
open sandy country with scattered trees and shrubs or occa-
sional thickets, which is found at Santarem and Monte- Alegre
on the lower Amazon, are examples, as well as the open
cultivated plains of Southern Celebes ; but in both cases the
forest country in adjacent districts has a moister and more
uniform climate, so that it seems probable that the nature of
the soil or the artificial clearing away of the forests, are
important agents in producing the departure from the typical
equatorial climate observed in such districts.

Effects of Vegetation on Climate

The almost rainless district of Ceara on the north-east coast
of Brazil, and only a few degrees south of the equator, is a strik-
ing example of the need of vegetation to react on the rainfall.
We have here no apparent cause but the sandy soil and bare
hills, which, when heated by the equatorial sun, produce ascend-
ing currents of warm air and thus prevent the condensation of
the atmospheric vapour, to account for such an anomaly ; and
there is probably no district where judicious planting would
produce such striking and beneficial effects. In Central India
the scanty and intermittent rainfall, with its fearful accom-
paniment of famine, is perhaps in great part due to the
absence of a sufficient proportion of forest -covering to the
earth's surface ; and it is by a systematic planting of all the
hill -tops, elevated ridges, and higher slopes that we shall
probably cure the evil. This would almost certainly induce
an increased rainfall ; but even more important and more
certain is the action of forests in checking evaporation from
the soil and causing perennial springs to flow, which may be
collected in vast storage tanks and serve to fertilise a great
extent of country ; whereas tanks without regular rainfall or

TROPICAL NATURE

permanent springs to supply them are worthless. In the
colder parts of the temperate zones the absence of forests is
not so much felt, because the hills and uplands are naturally
clothed with a thick coating of turf or peat which absorbs
moisture and does not become overheated by the sun's rays,
and the rains are seldom violent enough to strip this protect-
ive covering from the surface. In tropical and even in
warm -temperate countries, on the other hand, the rains are
periodical and often of excessive violence for a short period ;
and when the forests are cleared away the torrents of rain
soon strip off the vegetable soil, and thus destroy in a few
years the fertility which has been the growth of many cen-
turies. The bare subsoil becoming heated by the sun, every
particle of moisture which does not flow off is evaporated, and
this again reacts on the climate, producing long -continued
droughts only relieved by sudden and violent storms, which
add to the destruction and render all attempts at cultivation
unavailing. Wide tracts of fertile land in the south of Europe
have been devastated in this manner, and have become abso-
lutely uninhabitable. Knowingly to produce such disastrous
results would be a far more serious offence than any destruc-
tion of property which human labour has produced and can
replace ; yet we have ignorantly allowed such extensive clear-
ings for coffee cultivation in India and Ceylon as to cause
the destruction of much fertile soil, which human labour
cannot replace, and which will surely, if not checked in time,
lead to the deterioration of the climate and the permanent
impoverishment of the country. l

Short Twilight of the Equatorial Zone

One of the phenomena which markedly distinguish the
equatorial from the temperate and polar zones is the
shortness of the twilight and consequent rapid transition
from day to night and from night to day. As this depends
only on the fact of the sun descending vertically instead
of obliquely below the horizon, the difference is most
marked when we compare our midsummer twilight with

1 For a terrible picture of the irreparable devastation caused by the reckless
clearing of forests, see the third chapter of Mr. Marsh's work, The Earth as
Modified by Human Action.

i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 233

that of the tropics. Even with us the duration of twilight
is very much shorter at the time of the equinoxes, and
it is probably not much more than a third shorter than this
at the equator. Travellers usually exaggerate the short-
ness of the tropical twilight, it being sometimes said that if
we turn a page of the book we are reading when the
sun disappears, by the time we turn over the next page
it will be too dark to see to read. With an average book
and an average reader this is certainly not true, and it
will be well to describe as correctly as we can what really
happens.

In fine weather the air appears to be somewhat more
transparent near the equator than with us, and the intensity
of sunlight is usually very great up to the moment when the
solar orb touches the horizon. As soon as it has disappeared
the apparent gloom is proportionally great, but this hardly in-
creases perceptibly during the first ten minutes. During the
next ten minutes, however, it becomes rapidly darker, and at
the end of about half an hour from sunset the complete darkness
of night is almost reached. In the morning the changes are
perhaps even more striking. Up to about a quarter past five
o'clock the darkness is complete ; but about that time a few
cries of birds begin to break the silence of night, perhaps
indicating that signs of dawn are perceptible in the eastern
horizon. A little later the melancholy voices of the goat-
suckers are heard, varied croakings of frogs, the plaintive
whistle of mountain thrushes, and strange cries of birds or
mammals peculiar to each locality. About half-past five the
first glimmer of light becomes perceptible ; it slowly becomes
lighter, and then increases so rapidly that at about a quarter
to six it seems full daylight. For the next quarter of an
hour this changes very little in character ; when, suddenly, the
sun's rim appears above the horizon decking the dew-laden
foliage with glittering gems, sending gleams of golden light
far into the woods, and waking up all nature to life and
activity. Birds chirp and flutter about, parrots scream,
monkeys chatter, bees hum among the flowers, and gorgeous
butterflies flutter lazily along or sit with fully expanded
wings exposed to the warm and invigorating rays. The first
hour of morning in the equatorial regions possesses a charm

234 TROPICAL NATURE

and a beauty that can never be forgotten. All nature seems
refreshed and strengthened by the coolness and moisture of
the past night ; new leaves and buds unfold almost before the
eye, and fresh shoots may often be observed to have grown
many inches since the preceding day. The temperature is the
most delicious conceivable. The slight chill of early dawn,
which was itself agreeable, is succeeded by an invigorating
warmth ; and the intense sunshine lights up the glorious
vegetation of the tropics, and realises all that the magic art of
the painter or the glowing words of the poet have pictured as
their ideals of terrestrial beauty.

The Aspect of the Equatorial Heavens

Within the limits of the equatorial zone the noonday sun is
truly vertical twice every year, and for several months it passes
so near the zenith that the difference can hardly be detected
without careful observation of the very short shadows of vertical
objects. The absence of distinct horizontal shadows at noon,
which thus characterises a considerable part of the year, is
itself a striking phenomenon to an inhabitant of the temperate
zones ; and equally striking is the changed aspect of the starry
heavens. The grand constellation Orion passes vertically
overhead, while the Great Bear is only to be seen low down
in the northern heavens, and the Pole star either appears close
to the horizon or has altogether disappeared, according as we
are north or south of the equator. Towards the south the
Southern Cross, the Magellanic clouds, and the jet-black
" coal sacks " are the most conspicuous objects invisible in our
northern latitudes. The same cause that brings the sun
overhead in its daily march equally affects the planets, which
appear high up towards the zenith far more frequently than
with us, thus affording splendid opportunities for telescopic
observation.

Intensity of Meteorological Phenomena at the Equator
The excessive violence of meteorological phenomena gene-
rally supposed to be characteristic of the tropics is not by any
means remarkable in the equatorial zone. Electrical disturb-
ances are much more frequent, but not generally more violent
than in the temperate regions. The wind-storms are rarely

i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 235

of excessive violence, as might in fact be inferred from the
extreme steadiness of the barometer, whose daily range at
Batavia rarely exceeds one -eighth of an inch, while the
extreme range during three years was less than one-third of
an inch ! The amount of the rainfall is very great, seventy
or eighty inches in a year being a probable average ; and as
the larger part of this occurs during three or four months,
individual rainfalls are often exceedingly heavy. The greatest
fall recorded at Batavia during three years was three inches
and eighteenths in one hour,1 but this was quite exceptional,
and even half this quantity is very unusual. The greatest
rainfall recorded in twenty-four hours is seven inches and a
quarter ; but more than four inches in one day occurs only on
two or three occasions in a year. The blue colour of the
sky is probably not so intense as in many parts of the
temperate zone, while the brilliancy of the moon and stars is
not perceptibly greater than on our clearest frosty nights, and
is undoubtedly much inferior to what is witnessed in many
desert regions, and even in Southern Europe.

On the whole, then, we must decide that uniformity and
abundance, rather than any excessive manifestations, are the
prevailing characteristic of all the climatal phenomena of the
equatorial zone.

Concluding Eemarh

We cannot better conclude our account of the equatorial
climate than by quoting the following vivid description
of the physical phenomena which occur during the early
part of the dry season at Para. It is taken from Mr. Bates'
Naturalist on the Amazons, and clearly exhibits some of
the more characteristic features of a typical equatorial
day.

"At that early period of the day (the first two hours
after sunrise) the sky was invariably cloudless, the thermometer
marking 72° or 73° Fahr.; the heavy dew or the previous
night's rain, which lay on the moist foliage, becoming quickly
dissipated by the glowing sun, which, rising straight out of the
east, mounted rapidly towards the zenith. All nature was
fresh, new leaf and flower-buds expanding rapidly. . . . The

1 On 10th January 1867, from 1 to 2 A.M.

236 TROPICAL NATURE

heat increased hourly, and towards two o'clock reached 92° to
93° Fahr., by which time every voice of bird and mammal
was hushed. The leaves, which were so moist and fresh in
early morning, now became lax and drooping, and flowers shed
their petals. On most days in June and July a heavy shower
would fall some time in the afternoon, producing a most
welcome coolness. The approach of the rain-clouds was after
a uniform fashion very interesting to observe. First, the cool
sea-breeze which had commenced to blow about ten o'clock,
and which had increased in force with the increasing power
of the sun, would flag, and finally die away. The heat and
electric tension of the atmosphere would then become almost
insupportable. Languor and uneasiness would seize on every
one, even the denizens of the forest betraying it by their
motions. White clouds would appear in the east and gather
into cumuli, with an increasing blackness along their lower
portions. The whole eastern horizon would become almost
suddenly black, and this would spread upwards, the sun at
length becoming obscured. Then the rush of a mighty wind
is heard through the forest, swaying the tree-tops ; a vivid
flash of lightning bursts forth, then a crash of thunder, and
down streams the deluging rain. Such storms soon cease,
leaving bluish-black motionless clouds in the sky until night.
Meantime all nature is refreshed ; but heaps of flower-petals
and fallen leaves are seen under the trees. Towards evening
life revives again, and the ringing uproar is resumed from
bush and tree. The following morning the sun again rises
in a cloudless sky ; and so the cycle is completed ; spring,
summer, and autumn, as it were in one tropical day. The
days are more or less like this throughout the year. A
little difference exists between the dry and wet seasons ; but
generally the dry season, which lasts from July to December,
is varied with showers, and the wet, from January to June,
with sunny days. It results from this, that the periodical
phenomena of plants and animals do not take place at about
the same time in all species, or in the individuals of any given
species, as they do in temperate countries. In Europe a
woodland scene has its spring, its summer, its autumnal, and
its winter aspects. In the equatorial forests the aspect is the
same or nearly so every day in the year ; budding, flowering,

I CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 237

fruiting, and leaf-shedding are always going on in one species
or other. It is never either spring, summer, or autumn, but
each day is a combination of all three. With the day and
night always of equal length, the atmospheric disturbances of
each day neutralising themselves before each succeeding morn ;
with the sun in its course proceeding midway across the sky,
and the daily temperature almost the same throughout the
year — how grand in its perfect equilibrium and simplicity is
the march of Nature under the equator ! "

II

EQUATORIAL VEGETATION

The Equatorial Forest-Belt and its causes— General features of the Equa-
torial Forests— Characteristics of the Larger Forest-trees— Flowering
Trunks and their probable cause— Uses of Equatorial Forest-trees—
The Climbing Plants of the Equatorial Forests — Palms — Uses of Palm-
trees and their Products — Ferns — Ginger- worts and wild Bananas —
Arums — Screw-pines — Orchids — Bamboos — Uses of the Bamboo —
Mangroves — Sensitive-plants — Comparative Scarcity of Flowers —
Concluding Remarks on Tropical Vegetation.

IN the following sketch of the characteristics of vegetable life
in the equatorial zone, it is not intended to enter into any
scientific details or to treat the subject in the slightest degree
from a botanical point of view ; but merely to describe those
general features of vegetation which are almost or quite
peculiar to this region of the globe, and which are so general
as to be characteristic of the greater part of it rather than of
any particular country or continent within its limits.

The Equatorial Forest-Belt and its Causes

With but few and unimportant exceptions a great forest
band from a thousand to fifteen hundred miles in width girdles
the earth at the equator, clothing hill, plain, and mountain
with an evergreen mantle. Lofty peaks and precipitous
ridges are sometimes bare, but often the woody covering con-
tinues to a height of eight or ten thousand feet, as in some of
the volcanic mountains of Java and on portions of the Eastern
Andes. Beyond the forests both to the north and south, we
meet first with woody and then open country, soon changing
into arid plains or even deserts which form an almost con-

EQUATORIAL VEGETATION

tinuous band in the vicinity of the two tropics. On the line
of the tropic of Cancer we have, in America, the deserts and
dry plains of New Mexico; in Africa the Sahara; and in
Asia, the Arabian deserts, those of Beloochistan and Western
India, and farther east the dry plains of North China and
Mongolia. On the tropic of Capricorn we have, in America,
the Grand Chaco desert and the Pampas; in Africa, the
Kalahari desert and the dry plains north of the Limpopo ;
while the deserts and waterless plains of Central Australia
complete the arid zone. These great contrasts of verdure and
barrenness occurring in parallel bands all round the globe,
must evidently depend on the general laws which determine
the distribution of moisture over the earth, more or less
modified by local causes. Without going into meteorological
details, some of which have been given in the preceding
chapter, the main facts may be explained by the mode in
which the great aerial currents are distributed. The trade
winds passing over the ocean from north-east to south-west,
and from south-east to north-west, with an oblique tendency
towards the equator, become saturated with vapour, and are
ready to give out moisture whenever they are forced upwards
or in any other way have their temperature lowered. The
entire equatorial zone becomes thus charged with vapour-
laden air, which is the primary necessity of a luxuriant
vegetation. The surplus air (produced by the meeting of the
two trade winds) which is ever rising in the equatorial belt
and giving up its store of vapour, flows off north and south as
dry, cool air, and descends to the earth in the vicinity of the
tropics. Here it sucks up whatever moisture it meets with
and thus tends to keep this zone in an arid condition. The
trades themselves are believed to be supplied by descending
currents from the temperate zones, and these are at first
equally dry and only become vapour-laden when they have
passed over some extent of moist surface. At the solstices
the sun passes vertically over the vicinity of the tropics for
several weeks, and this further aggravates the aridity ; and
wherever the soil is sandy and there are no lofty mountain
chains to supply ample irrigation, the result is a more^or less
perfect desert. Analogous causes, which a study of aerial
currents will render intelligible, have produced other great

240 TROPICAL NATURE

forest-belts in the northern and southern parts of the tem-
perate zones; but owing to the paucity of land in the
southern hemisphere these are best seen in North America
and Northern Euro-Asia, where they form the great northern
forests of deciduous trees and of Coniferse. These being com-
paratively well known to us, will form the standard by a
reference to which we shall endeavour to point out and render
intelligible the distinctive characteristics of the equatorial
forest vegetation.

General Features of the Equatorial Forests
It is not easy to fix upon the most distinctive features of
these virgin forests, which nevertheless impress themselves
upon the beholder as something quite unlike those of temper-
ate lands, and as possessing a grandeur and sublimity altogether
their own. Amid the countless modifications in detail which
these forests present, we shall endeavour to point out the
chief peculiarities as well as the more interesting phenomena
which generally characterise them.

The observer new to the scene would perhaps be first
struck by the varied yet symmetrical trunks, which rise up
with perfect straightness to a great height without a branch,
and which, being placed at a considerable average distance apart,
give an impression similar to that produced by the columns
of some enormous building. Overhead, at a height, perhaps,
of a hundred and fifty feet, is an almost unbroken canopy of
foliage formed by the meeting together of these great trees
and their interlacing branches ; and this canopy is usually so
dense that but an indistinct glimmer of the sky is to be seen,
and even the intense tropical sunlight only penetrates to the
ground subdued and broken up into scattered fragments.
There is a weird gloom and a solemn silence, which combine
to produce a sense of the vast — the primeval — almost of the
infinite. It is a world in which man seems an intruder, and
where he feels overwhelmed by the contemplation of . the
ever-acting forces which, from the simple elements of the
atmosphere, build up the great mass of vegetation which
overshadows and almost seems to oppress the earth.

EQUATORIAL VEGETATION 241

Characteristics of the Larger Forest Trees

Passing from the general impression to the elements of
which the scene is composed, the observer is struck by the
great diversity of the details amid the general uniformity.
Instead of endless repetitions of the same forms of trunk
such as are to be seen in our pine, or oak, or beechwoods,
the eye wanders from one tree to another and rarely detects
two together of the same species. All are tall and upright
columns, but they differ from each other more than do the
columns of Gothic, Greek, and Egyptian temples. Some are
almost cylindrical, rising up out of the ground as if their
bases were concealed by accumulations of the soil ; others get
much thicker near the ground like our spreading oaks ; others
again, and these are very characteristic, send out towards the
base flat and wing-like projections. These projections are
thin slabs radiating from the main trunk, from which they
stand out like the buttresses of a Gothic cathedral. They
rise to various heights on the tree, from five or six to twenty
or thirty feet ; they often divide as they approach the ground,
and sometimes twist and curve along the surface for a con-
siderable distance, forming elevated and greatly compressed
roots. These buttresses are sometimes so large that the
spaces between them if roofed over would form huts capable
of containing several persons. Their use is evidently to give
the tree an extended base, and so assist the subterranean
roots in maintaining in an erect position so lofty a column
crowned by a broad and massive head of branches and foliage.
The buttressed trees belong to a variety of distinct groups.
Thus, many of the Bombacese or silk-cotton trees, several of
the Leguminosse, and perhaps many trees belonging to other
natural orders, possess these appendages.

There is another form of tree, hardly less curious, in
which the trunk, though generally straight and cylindrical, is
deeply furrowed and indented, appearing as if made up of a
number of small trees grown together at the centre. Some-
times the junction of what seem to be the component parts
is so imperfect that gaps or holes are left by which you can
see through the trunk in various places. At first one is dis-

R

242 TROPICAL NATURE n

posed to think this is caused by accident or decay, but re-
peated examination shows it to be due to the natural growth
of the tree. The accompanying outline sections of one of these
trees that was cut down exhibits its character. It was a
noble forest tree, more than two hundred feet high, but rather
slender in proportion, and it was by no means an extreme ex-
ample of its class. This peculiar form is probably produced
by the downward growth of aerial roots, like some New
Zealand trees whose growth has been traced, and of whose
different stages drawings may be seen at the Library of the Lin-
nsean Society. These commence their existence as parasitical

SECTIONS OF TRUNK OF A BORNEAN FOREST-TREE.
1. Section at seven feet from the ground. 2. 3. Sections much higher up.

climbers, which take root in the fork of some forest tree and
send down aerial roots which clasp round the stem that up-
holds them. As these roots increase in size and grow
together laterally they cause the death of their foster-parent.
The climber then grows rapidly, sending out large branches
above and spreading roots below, and as the supporting tree
decays away the aerial roots grow together and form a new
trunk, more or less furrowed and buttressed, but exhibiting
no other marks of its exceptional origin. Aerial-rooted forest
trees— like that figured in my Malay Archipelago (vol. i. p.
I— and the equally remarkable fig-trees of various species,

n EQUATORIAL VEGETATION 243

whose trunks are formed by a miniature forest of aerial roots,
sometimes separate, sometimes matted together, are charac-
teristic of the Eastern tropics, but appear to be rare or alto-
gether unknown in America, and can therefore hardly be
included among the general characteristics of the equatorial
zone.

Besides the varieties of form, however, the tree-trunks of
these forests present many peculiarities of colour and texture.
The majority are rather smooth -barked, and many are of
peculiar whitish, green, yellowish, or brown colours, or occa-
sionally nearly black. Some are perfectly smooth, others
deeply cracked and furrowed, while in a considerable number
the bark splits off in flakes or hangs down in long fibrous
ribands. Spined or prickly trunks (except of palms) are rare
in the damp equatorial forests. Turning our gaze upwards
from the stems to the foliage, we find two types of leaf not
common in the temperate zone, although the great mass of
the trees offer nothing very remarkable in this respect.
First, we have many trees with large, thick, and glossy leaves,
like those of the cherry -laurel or the magnolia, but even
larger, smoother, and more symmetrical. The leaves of the
Asiatic caoutchouc tree (Ficus elastica), so often cultivated in
houses, is a type of this class, which has a very fine effect
among the more ordinary-looking foliage. Contrasted with
this is the fine pinnate foliage of some of the largest forest
trees, which, seen far aloft against the sky, looks as delicate as
that of the sensitive mimosa.

Forest Trees of Low Growth

The great trees we have hitherto been describing form,
however, but a portion of the forest. Beneath their lofty
canopy there often exists a second forest of moderate-sized
trees, whose crowns, perhaps forty or fifty feet high, do not
touch the lowermost branches of those above them. These
are of course shade-loving trees, and their presence effectually
prevents the growth of any young trees of the larger kinds,
until, overcome by age and storms, some monarch of the
forest falls down, and, carrying destruction in its fall, opens
up a considerable space into which sun and air can penetrate.
Then comes a race for existence among the seedlings of the

244 TROPICAL NATURE

surrounding trees, in which a few ultimately prevail and fill
up the space vacated by their predecessor. Yet beneath this
second set of medium-sized forest trees there is often a third
undergrowth of small trees, from six to ten feet high, of dwarf
palms, of tree-ferns, and of gigantic herbaceous ferns. Yet
lower, on the surface of the ground itself, we find much variety.
Sometimes the earth is completely bare, a mass of decaying
leaves and twigs and fallen fruts. More frequently it is
covered with a dense carpet of selaginella or other lycopodi-
acese, and these sometimes give place to a variety of herba-
ceous plants, sometimes with pretty, but rarely with very
conspicuous flowers.

Flowering Trunks and their Probable Cause

Among the minor but not unimportant peculiarities that
characterise these lofty forests is the curious way in which
many of the smaller trees have their flowers situated on the
main trunk or larger branches instead of on the upper part
of the tree. The cacao-tree is a well-known example of this
peculiarity, which is not uncommon in tropical forests ; and
some of the smaller trunks are occasionally almost hidden by
the quantity of fruit produced on them. One of the most
beautiful examples of this mode of flowering is a small tree
of the genus Polyalthea, belonging to the family of the
custard-apples, not uncommon in the forests of north-western
Borneo. Its slender trunk, about fifteen or twenty feet high,
was completely covered with star-shaped flowers, three inches
across and of a rich orange-red colour, making the trees look
as if they had been artificially decorated with brilliant gar-
lands. The recent discoveries as to the important part played
by insects in the fertilisation of flowers offers a very probable
explanation of this peculiarity. Bees and butterflies are the
greatest flower -haunters. The former love the sun and fre-
quent open grounds or the flowery tops of the lofty forest
trees fully exposed to the sun and air. The forest shades are
frequented by thousands of butterflies, but these mostly keep
near the ground, where they have a free passage among the
tree-trunks and visit the flowering shrubs and herbaceous
plants. To attract these it is necessary that flowers should
be low down and conspicuous. If they grew in the usual

n EQUATORIAL VEGETATION 245

way on the .tops of these smaller trees overshadowed by the
dense canopy above them they would be out of sight of both
groups of insects ; but being placed openly on the stems, and
in the greatest profusion, they cannot fail to attract the atten-
tion of the wandering butterflies.

Uses of Equatorial Forest Trees

Amid this immense variety of trees, the natives have found
out such as are best adapted to certain purposes. The wood
of some is light and soft, and is used for floats or for carving
rude images, stools, and ornaments for boats and houses. The
flat slabs of the buttresses are often used to make paddles.
Some of the trees with furrowed stems are exceedingly strong
and durable, serving as posts for houses or as piles on which
the water -villages are built. Canoes, formed from a trunk
hollowed out and spread open under the action of heat require
one kind of wood, those built up with planks another ; and as
the species of trees in these forests are so much more numer-
ous than the wants of a semi-civilised population, there are
probably a large number of kinds of timber which will some
day be found to be well adapted to the special requirements
of the arts and sciences. The products of the trees of the
equatorial forests, notwithstanding our imperfect knowledge
of them, are already more useful to civilised man than to the
indigenous inhabitants. To mention only a few of those whose
names are tolerably familiar to us, we have such valuable
woods as mahogany, teak, ebony, lignum-vitae, purple -heart,
iron- wood, sandal- wood, and satin-wood ; such useful gums as
india-rubber, gutta-percha, tragacanth, copal, lac, and dammar ;
such dyes as are yielded by log-wood, brazil-wood, and sappan-
wood ; such drugs as the balsams of Capivi and Tolu, camphor,
benzoin, catechu or terra- japonica, cajuput oil, gamboge, quin-
ine, Angostura bark, quassia, and the urari and upas poisons ;
of spices we have cloves, cinnamon, and nutmegs ; and of
fruits, brazil-nuts, tamarinds, guavas, and the valuable cacao ;
while residents in our tropical colonies enjoy the bread-fruit,
avocado-pear, custard-apple, durian, mango, mangosteen, sour-
sop, papaw, and many others. This list of useful products
from the exogenous trees alone of the equatorial forests,
excluding those from the palms, shrubs, herbs, and creepers,

246 TROPICAL NATURE

might have been multiplied many times over by the introduc-
tion of articles whose names would be known only to those
interested in special arts or sciences ; but imperfect as it is, it
will serve to afford a notion of the value of this vast treasure-
house, which is as yet but very partially explored.

The Climbing Plants of the Equatorial Forests
Next to the trees themselves the most conspicuous and
remarkable feature of the tropical forests is the profusion of
woody creepers and climbers that everywhere meet the eye.
They twist around the slenderer stems, they drop down
pendent from the branches, they stretch tightly from tree
to tree, they hang looped in huge festoons from bough to
bough, they twist in great serpentine coils or lie in entangled
masses on the ground. Some are slender, smooth, and root-
like ; others are rugged or knotted ; often they are twined
together into veritable cables ; some are flat like ribands,
others are curiously waved and indented. Where they spring
from or how they grow is at first a complete puzzle. They
pass overhead from tree to tree, they stretch in tight cordage
like the rigging of a ship from the top of one- tree to the base
of another, and the upper regions of the forest often seem
full of them without our being able to detect any earth-
growing stem from which they arise. The conclusion is at
length forced upon us that these woody climbers must possess
the two qualities of very long life and almost indefinite longi-
tudinal growth, for by these suppositions alone can we explain
their characteristic features. The growth of climbers, even
more than all other plants, is upward towards the light. In
the shade of the forest they rarely or never flower, and seldom
even produce foliage, but when they have reached the summit
of the tree that supports them, they expand under the genial
influence of light and air, and often cover their foster-parent
with blossoms not its own. Here, as a rule, the climber's
growth would cease ; but the time comes when the supporting
tree rots and falls, and the creeper comes with it in torn and
tangled masses to the ground. But though its foster-parent
is dead it has itself received no permanent injury, but shoots
out again till it finds a fresh support, mounts another tree,
and again puts forth its leaves and flowers. In time the old

ii EQUATORIAL VEGETATION 247

tree rots entirely away and the creeper remains tangled on
the ground. Sometimes branches only fall and carry a por-
tion of the creeper tightly stretched to an adjoining tree ; at
other times the whole tree is arrested by a neighbour, to
which the creeper soon transfers itself in order to reach the
upper light. When by the fall of a branch the creepers are
left hanging in the air, they may be blown about by the
wind and catch hold of trees growing up beneath them, and
thus become festooned from one tree to another. When
these accidents and changes have been again and again
repeated the climber may have travelled very far from its
parent stem, and may have mounted to the tree tops and
descended again to the earth several times over. Only in
this way does it seem possible to explain the wonderfully
complex manner in which these climbing plants wander up
and down the forest as if guided by the strangest caprices, or
how they become so crossed and tangled together in the
wildest confusion.

The variety in the length, thickness, strength, and tough-
ness of these climbers enables the natives of tropical countries
to put them to various uses. Almost every kind of cordage
is supplied by them. Some will stand in water without rot-
ting, and are used for cables, for lines to which are attached
fish -traps, and to bind and strengthen the wooden anchors
used generally in the East. Boats and even large sailing
vessels are built, whose planks are entirely fastened together
by this kind of cordage skilfully applied to internal ribs. For
the better kinds of houses, smooth and uniform varieties are
chosen, so that the beams and rafters can be bound together
with neatness, strength, and uniformity, as is especially observ-
able among the indigenes of the Amazonian forests. When
baskets of great strength are required special kinds of creepers
are used ; and to serve almost every purpose for which we
should need a rope or a chain, the tropical savage adopts some
one of the numerous forest-ropes which long experience has
shown to have qualities best adapted for it. Some are smooth
and supple ; some are tough and will bear twisting or tying;
some will last longest in salt water, others in fresh ; one is
uninjured by the heat and smoke of fires, while another is
bitter or otherwise prejudicial to insect enemies.

248 TROPICAL NATURE

Besides these various kinds of trees and climbers, Avhich
form the great mass of the equatorial forests and determine
their general aspect, there are a number of forms of plants
which are always more or less present, though in some parts
scarce and in others in great profusion, and which largely aid
in giving a special character to tropical as distinguished from
temperate vegetation. Such are the various groups of palms,
ferns, ginger-worts, and wild plantains, arums, orchids, and
bamboos ; and under these heads we shall give a short account
of the part they take in giving a distinctive aspect to the
equatorial forests.

Palms

Although these are found throughout the tropics, and a
few species even extend into the warmer parts of the tem-
perate regions, they are yet so much more abundant and
varied within the limits of the region we are discussing that
they may be considered as among the most characteristic
forms of vegetation of the equatorial zone. They are, how-
ever, by no means generally present, and we may pass
through miles of forest without even seeing a palm. In other
parts they abound ; either forming a lower growth in the
lofty forest, or in swamps and on hillsides sometimes rising
up above the other trees. On river-banks they are especially
conspicuous and elegant, bending gracefully over the stream,
their fine foliage waving in the breeze, and their stems often
draped with hanging creepers.

The chief feature of the palm tribe consists in the
cylindrical trunk crowned by a mass of large and somewhat
rigid leaves. They vary in height from a few feet to that of
the loftiest forest trees. Some are stemless, consisting only
of a spreading crown of large pinnate leaves ; but the great
majority have a trunk slender in proportion to its height.
Some of the smaller species have stems no thicker than
a lead pencil, and four or five feet high; while the great
Mauritia of the Amazon has a trunk full two feet in dia-
meter, and more than one hundred feet high. Some
species probably reach a height of two hundred feet, for
Humboldt states that in South America he measured a
palm, which was one hundred and ninety-two English feet

" EQUATORIAL VEGETATION 249

high. The leaves of palms are often of immense size.
Those of the Manicaria saccifera of Para are thirty feet long
and four or five feet wide, and are not pinnate but entire
and very rigid. Some of the pinnate leaves are much larger,
those of the Raphia teedigera and Maximiliana regia being
both sometimes more than fifty feet long. The fan-shaped
leaves of other species are ten or twelve feet in diameter.
The trunks of palms are sometimes smooth and more or less
regularly ringed, but they are frequently armed with dense
prickles which are sometimes eight inches long. In some
species the leaves fall to the ground as they decay, leaving a
clean scar, but in most cases they are persistent, rotting
slowly away, and leaving a mass of fibrous stumps attached
to the upper part of the stem. This rotting mass forms an
excellent soil for ferns, orchids, and other semi -parasitical
plants, which form an attractive feature on what would
otherwise be an unsightly object. The sheathing margins of
the leaves often break up into a fibrous material, sometimes
resembling a coarse cloth, and in other cases more like horse-
hair. The flowers are not individually large, but form large
spikes or racemes, and the fruits are often beautifully scaled
and hang in huge bunches, which are sometimes more than a
load for a strong man. The climbing palms are very remark-
able, their tough, slender, prickly stems mounting up by means
of the hooked midribs of the leaves to the tops of the
loftiest forest trees, above which they send up an elegant
spike of foliage and flowers. The most important are the
American Desmoncus and the Eastern Calamus, the latter
being the well-known rattan or cane of which chair-seats are
made, from the Malay name " rotang." The rattan-palms
are the largest and most remarkable of the climbing group.
They are very abundant in the drier equatorial forests, and
more than sixty species are known from the Malay Archi-
pelago. The stems (when cleaned from the sheathing leaves
and prickles) vary in size, from the thickness of a quill to
that of the wrist; and where abundant they render the
forest almost impassable. They lie about the ground coiled
and twisted and looped in the most fantastic manner. They
hang in festoons from trees and branches, they rise suddenly
through mid air up to the top of the forest, or coil loosely

250 TROPICAL NATURE n

over shrubs and in thickets like endless serpents. They must
attain an immense age, and apparently have almost unlimited
powers of growth, for some are said to have been found
which were six hundred or even one thousand feet long, and
if so they are probably the longest of all vegetable growths.
The mode in which such great lengths and tangled convolu-
tions have been attained has already been explained in the
general account of woody climbers. From the immense
strength of these canes and the facility with which they can
be split, they are universally used for cordage in the countries
where they grow in preference to any other climbers, and
immense quantities are annually exported to all parts of the
world.

Uses of Palm-trees and their Products

To the natives of the equatorial zone the uses of palms
are both great and various. The fruits of several species
— more especially the cocoa-nut of the East and the peach-
nut (Guilielma speciosa) of America — furnish abundance of
wholesome food, and the whole interior of the trunk of the
sago palm is converted into an edible starch — our sago.
Many other palm -fruits yield a thin pulp, too small in
quantity to be directly eaten, but which, when rubbed off
and mixed with a proper quantity of water, forms an exceed-
ingly nutritious and agreeable article of food. The most
celebrated of these is the assai of the Amazon, made from the
fruit of Euterpe oleracea, and which, as a refreshing, nourish-
ing, and slightly stimulating beverage for a tropical country,
takes the place of our chocolate and coffee. A number of
other palms yield a similar product, and many that are not
eaten by man are greedily devoured by a variety of animals,
so that the amount of food produced by this tribe of plants
is much larger than is generally supposed.

The sap which pours out of the cut flower-stalk of several
species of palm, when slightly fermented, forms palm-wine or
toddy, a very agreeable drink ; and when mixed with various
bitter herbs or roots which check fermentation, a fair imita-
tion of beer is produced. If the same fluid is at once boiled
and evaporated it produces a quantity of excellent sugar.
The Arenga saccharifera, or sugar-palm of the Malay coun-
tries, is perhaps the most productive of sugar. A single tree

n EQUATORIAL VEGETATION 251

will continue to pour out several quarts of sap daily for
weeks together, and where the trees are abundant this forms
the chief drink and most esteemed luxury of the natives. A
Dutch chemist, Mr. De Vry, who has studied the subject in
Java, believes that great advantages would accrue from the
cultivation of this tree in place of the sugar-cane. According
to his experiments it would produce an equal quantity of
sugar of good quality with far less .labour and expense, be-
cause no manure and no cultivation would be required, and
the land will never be impoverished, as it so rapidly becomes
by the growth of sugar-cane. The reason of this difference
is, that the whole produce of a cane-field is taken off the
ground, the crushed canes being burnt; and the soil thus
becomes exhausted of the various salts and minerals which
form part of the woody fibre and foliage. These must be
restored by the application of manure, and this, together
with the planting, weeding, and necessary cultivation, is very
expensive. With the sugar-palm, however, nothing whatever
is taken away but the juice itself ; the foliage falls on the
ground and rots, giving back to it what it had taken ; and
the water and sugar in the juice being almost wholly derived
from the carbonic acid and aqueous vapour of the atmos-
phere, there is no impoverishment ; and a plantation of these
palms may be kept up on the same ground for an indefinite
period. Another most important consideration is, that these
trees will grow on poor rocky soil and on the steep slopes of
ravines and hillsides, where any ordinary cultivation is im-
possible, and a great extent of fertile land would thus be set
free for other purposes. Yet further, the labour required for
such sugar plantations as these would be of a light and inter-
mittent kind, exactly suited to a semi - civilised people, to
whom severe and long-continued labour is never congenial.
This combination of advantages appears to be so great that it
seems possible that the sugar of the world may in the future
be produced from what would otherwise be almost waste
ground ; and it is to be hoped that the experiment will soon
be tried in some of our tropical colonies, more especially as
an Indian palm, Phoenix sylvestris, also produces abundance
of sugar, and might be tried in its native country.

Other articles of food produced from palms are, cooking-

252 TROPICAL NATURE

oil from the cocoa-nut and baccaba palm, salt from the fruit
of a South American palm (Leopoldinia major), while the
terminal bud or " cabbage " of many species is an excellent
and nutritious vegetable ; so that palms may be said to supply
bread, oil, sugar, salt, fruit, and vegetables. Oils for various
other purposes are made from several distinct palms, especially
from the celebrated oil palm of West Africa, while wax is
secreted from the leaves of some South American species;
the resin called Dragon's blood is the product of one of the
rattan palms. The fruit of the Areca palm is the " betel-nut "
so universally chewed by the Malays as a gentle stimulant,
and is their substitute for the opium of the Chinese, the
tobacco of Europeans, and the coca-leaf of South America.

For thatching purposes the leaves of palms are invaluable,
and are universally used wherever they are abundant ; and
the petioles or leaf stalks, often fifteen or twenty feet long,
are used as rafters, or when fastened together with pegs form
doors, shutters, partitions, or even the walls of entire houses.
They are wonderfully light and strong, being formed of a
dense pith covered with a hard rind or bark, and when split
up and pegged together serve to make many kinds of boxes,
which, when covered with the broad leaves of a species of screw-
pine and painted or stained of various colours, are very strong
and serviceable as well as very ornamental. Ropes and cables
are woven from the black fibrous matter that fringes the
leaves of the sugar-palm and some other species, while fine
strings of excellent quality, used even for bow-strings, fishing-
lines, and hammocks, are made of fibres obtained from the
unopened leaves of some American species. The fibrous
sheath at the base of the leaves of the cocoa-nut palm is so
compact and cloth-like that it is used for a variety of purposes,
as for strainers, for wrappers, and to make very good hats.
The great woody spathes of the larger palms serve as natural
baskets, as cradles, or even as cooking-vessels in which water
may be safely boiled. The trunks form excellent posts and
fencing, and when split make good flooring. Some species
are used for bows, others for blow-pipes ; the smaller palm-
spines are sometimes used as needles or to make fish-hooks,
and the larger as arrows. To describe in detail all the uses
to which palm-trees and their products are applied in various

n EQUATORIAL VEGETATION 253

parts of the world might occupy a volume ; but the preceding
sketch will serve to give an idea of how important a part is
filled by this noble family of plants, whether we regard them
as a portion of the beautiful vegetation of the tropics, or in
relation to the manners and customs, the lives and the well-
being, of the indigenous inhabitants.

Ferns

The type of plants which, next to palms, most attracts
attention in the equatorial zone is perhaps that of the
ferns, which here display themselves in vast profusion and
variety. They grow abundantly on rocks and on decaying
trees ; they clothe the sides of ravines and the margins of
streams ; they climb up the trees and over bushes ; they form
tufts and hanging festoons among the highest branches.
Some are as small as mosses, others have huge fronds eight or
ten feet long, while in mountainous districts the most elegant
of the group, the tree-ferns, bear their graceful crowns on
slender stems twenty to thirty, or even fifty feet high. It is
this immense variety rather than any special features that
characterises the fern -vegetation of the tropics. We have
here almost every conceivable modification of size, form of.
fronds, position of spores, and habit of growth, in plants that
still remain unmistakably ferns. Many climb over shrubs
and bushes in a most elegant manner ; others cling closely
to the bark of trees like ivy. The great birds'- nest fern
(Platycerium) attaches its shell-like fronds high up on the
trunks of lofty trees. Many small terrestrial species have
digitate, or ovate, or ivy -shaped, or even whorled fronds,
resembling at first sight those of some herbaceous flowering
plants. Their numbers may be judged from the fact that in
the vicinity of Tarrapoto, in Peru, Dr. Spruce gathered two
hundred and fifty species of ferns, while the single volcanic
mountains of Pangerango in Java (ten thousand feet high) is
said to have produced three hundred species.

Ginger-worts and wild Bananas

These plants, forming tlie families Zingiberaceae and
Musacese of botanists, are very conspicuous ornaments of the
equatorial forests, on account of their large size, fine foliage,

254 TROPICAL NATURE

and handsome flowers. The bananas and plantains are well
known as among the most luxuriant and beautiful productions
of the tropics. Many species occur wild in the forests ; all
have majestic foliage and handsome flowers, while some pro-
duce edible fruit. Of the ginger-worts (Zingiberaceae and
Marantacese), the well-known cannas of our sub -tropical
gardens may be taken as representatives, but the equatorial
species are very numerous and varied, often forming dense
thickets in damp places, and adorning the forest shades with
their elegant and curious or showy flowers. The maranths
produce "arrowroot," while the ginger -worts are highly
aromatic, producing ginger, cardamums, grains of paradise,
turmeric, and several medicinal drugs. The Musaceae pro-
duce the most valuable of tropical fruits and foods. The
banana is the variety which is always eaten as a fruit, having
a delicate aromatic flavour ; the plantain is a larger variety,
which is best cooked. Eoasted in the green state it is an
excellent vegetable, resembling roasted chestnuts ; when ripe
it is sometimes pulped and boiled with water, making a very
agreeable sweet soup ; or it is roasted, or cut into slices and
fried, in either form being a delicious tropical substitute for
fruit pudding. These plants are annuals, producing one im-
mense bunch of fruit. This bunch is sometimes four or five feet
long, containing near two hundred plantains, and often weighs
about a hundredweight. They grow very close together, and
Humboldt calculated that an acre of plantains would supply
more food than could be obtained from the same extent of
ground by any other known plant. Well may it be said that
the plantain is the glory of the tropics, and well was the
species named by Linnaeus — Musa paradisiaca !

Another very characteristic and remarkable group of
tropical plants are the epiphytal and climbing arums.
These are known by their large, arrow-shaped, dark green
and glossy leaves, often curiously lobed or incised, and
sometimes reticulated with large open spaces, as if pieces had
been regularly eaten out of them by some voracious insects.
Sometimes they form clusters of foliage on living or dead
trees, to which they cling by their aerial roots. Others climb

n EQUATORIAL VEGETATION 255

up the smooth bark of large trees, sending out roots as they
ascend which clasp around the trunk. Some mount straight
up, others wind round the supporting trunks, and their large,
handsome, and often highly remarkable leaves, which spread
out profusely all along the stem, render them one of the most
striking forms of vegetation which adorn the damper and more
luxuriant parts of the tropical forests of both hemispheres.

Screw-pines

These singular plants, constituting the family Pandanaceas
of botanists, are very abundant in many parts of the Eastern
tropics, while they are comparatively scarce in America.
They somewhat resemble Yuccas, but have larger leaves,
which grow in a close spiral screw on the stem. Some are
large and palm-like, and it is a curious sight to stand under
these and look up at the huge vegetable screw formed by
the bases of the long, drooping leaves. Some have slender
branched trunks, which send out aerial roots ; others are
stemless, consisting of an immense spiral cluster of stiff leaves
ten or twelve feet long and only two or three inches wide.
They abound most in sandy islands, while the larger species
grow in swampy forests. Their large-clustered fruits, some-
thing like pine-apples, are often of a red colour; and their
long, stiff leaves are of great use for covering boxes and for
many other domestic uses.

Orchids

These interesting plants, so well known from the ardour
with which they are cultivated on account of their beautiful
and singular flowers, are pre-eminently tropical, and are
probably more abundant in the mountains of the equatorial
zone than in any other region. Here they are almost omni-
present in some of their countless forms. They grow on the
stems, in the forks or on the branches of trees ; they abound
on fallen trunks ; they spread over rocks, or hang down the
face of precipices; while some, like our northern species,
grow on the ground among grass and herbage. Some trees
whose bark is especially well adapted for their support are
crowded with them, and these form natural orchid-gardens.
Some orchids are particularly fond of the decaying leaf-stalks

256 TROPICAL NATURE

of palms or of tree-ferns. Some grow best over water, others
must be elevated on lofty trees and well exposed to sun and
air. The wonderful variety in the form, structure, and colour
of the flowers of orchids is well known ; but even our finest
collections give an inadequate idea of the numbers of these
plants that exist in the tropics, because a large proportion of
them have quite inconspicuous flowers and are not worth
cultivation. More than thirty years ago the number of known
orchids was estimated by Dr. Lindley at three thousand species,
in Bentham and Hooker's Genera Plantarum at five thousand,
and it is not improbable that they may be now nearly six
thousand. But whatever may be the numbers of the collected
and described orchids, those that still remain to be discovered
must be enormous. Unlike ferns, the species have a very
limited range, and it would require the systematic work of a
good botanical collector during several years to exhaust any
productive district — say such an island as Java — of its orchids.
It is not therefore at all improbable that this remarkable
group may ultimately prove to be the most numerous in
species of all the families of flowering plants.

Although there is a peculiarity of habit that enables one
soon to detect an orchidaceous plant even when not in flower,
yet they vary greatly in size and aspect. Some of the small
creeping species are hardly larger than mosses, while the larger
Grammatophyllums of Borneo, which grow in the forks of trees,
form a mass of leafy stems ten feet long, and some of the
terrestrial species — as the American Sobralias — grow erect to
an equal height. The fleshy aerial roots of most species give
them a very peculiar aspect, as they often grow to a great
length in the open air, spread over the surface -of rocks, or
attach themselves loosely to the bark of trees, extracting
nourishment from the rain and from the aqueous vapour of
the atmosphere. Yet notwithstanding the abundance and
variety of orchids in the equatorial forests, they seldom
produce much effect by their flowers. This is due partly to
the very large proportion of the species having quite incon-
spicuous flowers ; and partly to the fact that the flowering
season for each kind lasts but a few weeks, while different
species flower almost every month in the year. It is also
due to the manner of growth of orchids, generally in single

ii EQUATORIAL VEGETATION 257

plants or clumps, which are seldom large or conspicuous
as compared with the great mass of vegetation around them.
It is only at long intervals that the traveller meets with any-
thing which recalls the splendour of our orchid-houses and
flower shows. The slender-stalked golden Oncidiums of the
flooded forests of the Upper Amazon ; the grand Cattleyas of
the drier forests ; the Caelogynes of the swamps, and the re-
markable Vanda lowii of the hill forests of Borneo, — are the
chief examples of orchid beauty that have impressed them-
selves on the memory of the present writer during twelve
years' wandering in tropical forests. The last-named plant is
unique among orchids, its comparatively small cluster of leaves
sending out numerous flower -stems, which hang down like
cords to a length of eight feet, and are covered with numbers
of large star-like crimson-spotted flowers.

Bamboos

The gigantic grasses called bamboos can hardly be classed
as typical plants of the tropical zone, because they appear to
be rare in the entire African continent and are comparatively
scarce in South America. They also extend beyond the
geographical tropics in China and Japan as well as in Northern
India. It is, however, within the tropics and towards the
equator that they attain their full size and beauty, and it is
here that the species are most numerous and offer that variety
of form, size, and quality which renders them so admirable a
boon to man. A fine clump of large bamboos is perhaps the
most graceful of all vegetable forms, resembling the light and
airy plumes of the bird of paradise copied on a gigantic scale
in living foliage. Such clumps are often eighty or a hundred
feet high, the glossy stems, perhaps six inches thick at the
base, springing up at first straight as an arrow, tapering
gradually to a slender point, and bending over in elegant
curves with the weight of the slender branches and grassy
leaves. The various species differ greatly in size and propor-
tions, in the comparative length of the joints, in the thickness
and strength of the stem-walls, in their straightness, smooth-
ness, hardness, and durability. Some are spiny, others are
unarmed ; some have simple stems, others are thickly set with
branches ; while some species even grow in such an irregular,

258 TROPICAL NATURE

zigzag, branched manner as to form veritable climbing bam-
boos. They generally prefer dry and upland stations, though
some grow near the banks of rivers, and a few in the thick
forests, and, in South America, in flooded tracts. They often
form dense thickets where the forests have been cleared away,
and owing to their great utility they are cultivated or pre-
served near native houses and villages, and in such situations
often give a finishing charm to the landscape.

Uses of the Bamboo

Perhaps more than any other single type of vegetation, the
bamboo seems specially adapted for the use of half-civilised
man in a wild tropical country ; and the purposes to which it
is applied are almost endless. It is a natural column or
cylinder, very straight, uniform in thickness, of a compact and
solid texture, and with a smooth, flinty, naturally -polished,
external skin. It is divided into ringed joints at regular
intervals which correspond to septa or partitions within, so
that each joint forms a perfectly closed and water-tight vessel.
Owing to its hollowness, the hardness of the external skin,
and the existence of the joints and partitions, it is wonder-
fully strong in proportion to its weight. It can be found of
many distinct sizes and proportions, light or heavy, long or
short-jointed, and varying from the size of a reed to that of a
tall and slender palm-tree. It can be split with great facility
and accuracy, and, owing to its being hollow, it can be easily
cut across or notched with a sharp knife or hatchet. It is
excessively strong and highly elastic, and whether green or
dry is almost entirely free from any peculiar taste or smell.
The way in which these various qualities of the bamboo
render it so valuable will be best shown by giving a brief
account of some of the uses to which it is applied in the
Malay Archipelago.

Several effective weapons are easily made from bamboo.
By cutting off the end very obliquely just beyond a joint, a
very sharp cutting point is produced suitable for a spear,
dagger, or arrow-head, and capable of penetrating an animal's
body as readily as iron. Such spears are constantly used by
many of the Malay tribes. In the eastern half of the Archi-
pelago, where bows and arrows are used, these weapons are

n EQUATORIAL VEGETATION 259

often formed entirely of bamboo. The harder and thicker
sorts, split and formed with tapering ends, make a very
strong and elastic bow, while a narrow strip of the outer skin
of the same is used for the string, and the slender reed-like
kinds make excellent arrows. One of the few agricultural
tools used by the Papuans — a spud or hoe for planting or
weeding — is made of a stout bamboo cut somewhat like the
spear.

For various domestic purposes the uses of bamboo are
endless. Ladders are rapidly made from two bamboo poles
of the required length, by cutting small notches just above
each ring, forming holes to receive the rungs or steps formed
of a slenderer bamboo. For climbing lofty trees to get bees-
wax, a temporary ladder reaching to any height is ingeniously
formed of bamboo. One of the hardest and thickest sorts is
chosen, and from this a number of pegs about a foot long are
made. These are sharpened at one end and then driven into
the tree in a vertical line about three feet apart. A tall and
slender bamboo is then placed upright on the ground and
securely tied with rattan or other cords to the heads of these
pegs, which thus with the tree itself form a ladder. A man
mounts these steps and builds up the ladder as he goes,
driving in fresh pegs and splicing on fresh bamboos till he
reaches the lower branches of the tree, which is sometimes
eighty or a hundred feet from the ground. As the weight of
the climber is thrown on several of the pegs which are bound
together and supported by the upright bamboo, this ladder is
much safer than it looks at first sight, and it is made with
wonderful rapidity. When a path goes up a steep hill over
smooth ground, bamboo steps are often laid down to prevent
slipping while carrying heavy loads. These are made with
uniform lengths of stout bamboo in which opposite notches
are cut at each end just within a joint. These notches allow
strong bamboo pegs to be driven through into the ground,
thus keeping the steps securely in place. The masts and
yards of native vessels are almost always formed of bamboo,
as it combines lightness, strength, and elasticity in an
unequalled degree. Two or three large bamboos also form
the best outriggers to canoes on account of their great buoy-
ancy. They also serve to form rafts; and in the city of

TROPICAL NATURE

Palembang, in Sumatra, there is a complete street of floating
houses supported on rafts formed of huge bundles of bamboos.
Bridges across streams or to carry footpaths along the face of
precipices are constructed by the Dyaks of Borneo wholly of
bamboos, and some of these are very ingeniously hung from
overhanging trees by diagonal rods of bamboo, so as to form
true suspension bridges. The flooring of Malay houses is
almost always of bamboo, but is constructed in a variety of
ways. Generally large bamboos are used, split lengthways
twice and the pieces tied down with rattan. This forms a
grated floor, slightly elastic, and very pleasant to the bare-
footed natives. A superior floor is sometimes formed of slabs,
which are made from very stout bamboos cut into lengths of
about three or four feet and split down one side. The joints
are then deeply and closely notched all round with a sharp
chopping-knif e, so that the piece can be unrolled as it were
and pressed flat, when it forms a hard board with a natural
surface, which, with a little wear, becomes beautifully smooth
and polished. Blinds, screens, and mats are formed of bam-
boos in a variety of ways, — sometimes of thin kinds crushed
flat and plaited, but more frequently of narrow strips con-
nected together with cords of bamboo-bark or rattan. Strips
of bamboo supported on cross-pieces form an excellent bed,
which from its elasticity supplies the purpose of a mattress as
well, and only requires a mat laid over it to insure a comfort-
able night's repose. Every kind of basket, too, is made of
bamboo, from the coarsest heavy kinds to such as are fine and
ornamental. In such countries as Lombock and Macassar,
where the land is much cultivated and timber scarce, entire
houses are built of bamboo, — posts, walls, floors, and roofs all
being constructed of this one material; and perhaps in no
other way can so elegant and well-finished a house be built so
quickly and so cheaply. Almost every kind of furniture is
also made of the same material, excellent bamboo chairs, sofas,
and bedsteads being made in the Moluccas, which, for appear-
ance, combined with cheapness, are probably unsurpassed in
the world. A chair costs sixpence, and a sofa two shillings.

Among simpler uses bamboos are admirably adapted for
water-vessels. Some of the lighter sorts are cut into lengths
of Wbout five feet, a small hole being knocked through the

n EQUATORIAL VEGETATION 261

septa of the joints. This prevents the water from running
out too quickly, and facilitates its being poured out in a
regulated stream to the last drop. Three or four of these
water-vessels are tied together and carried on the back, and
they stand very conveniently in a corner of the hut. Water-
pipes and aqueducts are also readily made from bamboo tubes
supported at intervals on two smaller pieces tied crosswise.
In this way a stream of water is often conveyed from some
distance to the middle of a village. Measures for rice or
palm-wine, drinMng-vessels, and water-dippers, are to be found
almost ready-made in a joint of bamboo ; and when fitted
with a cap or lid they form tobacco or tinder-boxes. Perches
for parrots, with food and water vessels, are easily made out
of a single piece of bamboo, while with a little more labour
elegant bird -cages are constructed. In Timor a musical
instrument is formed from a single joint of a large bamboo
by carefully raising seven strips of the hard skin to form
strings, which remain attached at both ends and are elevated
by small pegs wedged underneath, the strings being prevented
from splitting off by a strongly-plaited ring of a similar mate-
rial bound round each end. An opening cut on one side
allows the bamboo to vibrate in musical notes when the harp-
like strings are sharply pulled with the fingers. In Java
strips of bamboo supported on stretched strings and struck
with a small stick produce the higher notes in the "game-
lung " or native band, which consists mainly of sets of gongs
and metallic plates of various sizes. Almost all the common
Chinese paper is made from the foliage and stems of some
species of bamboo, while the young shoots, as they first spring
out of the ground, are an excellent vegetable, quite equal to
artichokes. Single joints of bamboo make excellent cooking-
vessels while on a journey. Rice can be boiled in them to
perfection, as well as fish and vegetables. They serve too for
jars in which to preserve sugar, salt, fruit, molasses, and
cooked provisions ; and for the smoker, excellent pipes and
hookahs can be formed in a few minutes out of properly
chosen joints of bamboo.

These are only a sample of the endless purposes to which
the bamboo is applied in the countries of which it is a
native, its chief characteristic being that in a few minutes it

TROPICAL NATURE

can be put to uses which, if ordinary wood were used, would
require hours or even days of labour. There is also a regu-
larity and a finish about it which is found in hardly any other
woody plant; and its smooth and symmetrically ringed
surface gives an appearance of fitness and beauty to its
varied applications. On the whole, we may perhaps consider
it as the greatest boon which nature gives to the natives of
the eastern tropics.

Mangroves

Among the forms of plants which are sure to attract
attention in the tropics are the mangroves, which grow
between tide-marks on coasts and estuaries. These are low
trees with widely-spreading branches and a network of aerial
roots a few feet above the ground ; but their most remarkable
peculiarity is, that their fruits germinate on the tree, sending
out roots and branches before falling into the muddy soil —
a completely formed plant. In some cases the root reaches
the ground before the seed above falls off. These trees
greatly aid the formation of new land, as the mass of aerial
roots which arch out from the stem to a considerable distance
collects mud and floating refuse, and so raises and consoli-
dates the shore ; while the young plants, often dropping from
the farthest extremity of the branches, rapidly extend the
domain of vegetation to the farthest possible limits. The
branches, too, send down slender roots like those of the
banyan, and become independent trees. Thus a complete
woody labyrinth is formed ; and the network of tough roots
and stems resists the action of the tides, and enables the
mud brought down by great tropical rivers to be converted
into solid land far more rapidly than it could be without
this aid.

Sensitive Plants

Among the more humble forms of vegetation that attract
the traveller's notice none are more interesting than the
sensitive species of Mimosa. These are almost all natives of
South America, but one species, Mimosa pudica, has spread
to Africa and Asia, so that sensitive plants now abound as
wayside weeds in many parts both of the eastern and west-
ern tropics, sometimes completely carpeting the ground with

n .EQUATORIAL VEGETATION 263

their delicate foliage. Where a large surface of ground is
thus covered the effect of walking over it is most peculiar.
At each step the plants for some distance round suddenly
droop, as if struck with paralysis, and a broad track of
prostrate herbage, several feet wide, is distinctly marked out
by the different colour of the closed leaflets. The explana-
tion of this phenomenon given by botanists is not very
satisfactory ; l while the purpose or use of the peculiarity is
still more mysterious, seeing that out of more than two
hundred species belonging to this same genus Mimosa, only
a small number are sensitive in any remarkable degree, and
in the whole vegetable kingdom there are but few other
plants which possess more than the rudiments of a similar
property. The true sensitive plants are all low-growing herbs
or shrubs with delicate foliage, which might possibly be liable
to destruction by herbivorous animals, a fate which they may
perhaps escape by their singular power of suddenly collapsing
before the jaws opened to devour them. The fact that one
species has been naturalised as a weed over so wide an area
in the tropics, seems to show that it possesses some ad-
vantage over the generality of tropical weeds. It is, however,
curious that, as the most sensitive species of Mimosa are
somewhat prickly, so easy and common a mode of protec-
tion as the development of stronger spines should here
have failed ; and that its place should be supplied by so
singular a power as that of simulating death in a manner
which suggests the possession of both sensation and volun-
tary motion.

Comparative Scarcity of Flowers

It is a very general opinion among inhabitants of our
temperate climes that amid the luxuriant vegetation of the
tropics there must be a grand display of floral beauty, and
this idea is supported by the number of large and showy
flowers cultivated in our hothouses. The fact is, however,
that in proportion as the general vegetation becomes more
luxuriant, flowers form a less and less prominent feature ;
and this rule applies not only to the tropics but to the tem-

1 See Nature, vol. xvL p. 349, where the German botanist Pfeffer's theory
is given.

264 TROPICAL NATURE

perate and frigid zones. It is amid the scanty vegetation of
the higher mountains and towards the limits of perpetual
snow that the alpine flowers are most brilliant and conspicu-
ous. Our own meadows and pastures and hillsides produce
more gay flowers than our woods and forests ; and, in the
tropics, it is in the parts where vegetation is less dense and
luxuriant that flowers most abound. In the damp and
uniform climate of the equatorial zone the mass of vegeta-
tion is greater and more varied than in any other part of the
globe, but in the great virgin forests themselves flowers are
rarely seen. After describing the forests of the Lower
Amazon, Mr. Bates asks : " But where were the flowers ?
To our great disappointment we saw none, or only such as
were insignificant in appearance. Orchids are rare in the
dense forests of the lowlands, and I believe it is now tolerably
well ascertained that the majority of the forest trees in
equatorial Brazil have small and inconspicuous flowers."1
My friend Dr. Eichard Spruce assured me that by far the
greater part of the plants gathered by him in equatorial
America had inconspicuous green or white flowers. My own
observations in the Aru Islands for six months, and in Borneo
for more than a year, while living almost wholly in the
forests, are quite in accordance with this view. Conspicuous
masses of showy flowers are so rare that weeks and months
may be passed without observing a single flowering plant
worthy of special admiration. Occasionally some tree or
shrub will be seen covered with magnificent yellow or
crimson or purple flowers, but it is usually an oasis of colour
in a desert of verdure, and therefore hardly affects the
general aspect of the vegetation. The equatorial forest is too
gloomy for flowers or generally even for much foliage, except
of ferns and other shade-loving plants ; and were it not that
the forests are broken up by rivers and streams, by mountain
ranges, by precipitous rocks and by deep ravines, there would
be far fewer flowers visible than there are. Some of the
great forest trees have showy blossoms, and when these are
seen from an elevated point looking over an expanse of tree-
tops the effect is very grand ; but nothing is more erroneous
than the statement sometimes made that tropical forest trees
1 The Naturalist on the River Amazons, 2d ed., p. 38.

ii EQUATORIAL VEGETATION „ 265

generally have showy flowers, for it is doubtful whether the
proportion is at all greater in tropical than in temperate
zones. On such natural exposures as steep mountain sides,
the banks of rivers, or ledges of precipices, and on the
margins of such artificial openings as roads and forest clear-
ings, whatever floral beauty is to be found in the more
luxuriant parts of the tropics is exhibited. But even in such
favourable situations it is not the abundance and beauty of
the flowers but the luxuriance and the freshness of the foliage,
and the grace and infinite variety of the forms of vegetation,
that will most attract the attention and extort the admiration
of the traveller. Occasionally indeed you will come upon
shrubs gay with blossoms or trees festooned with flowering
creepers; but, on the other hand, you may travel for a
hundred miles and see nothing but the varied greens of the
forest foliage and the deep gloom of its tangled recesses. In
Mr. Belt's. Naturalist in Nicaragua, he thus describes the
great virgin forests of that country which, being in a mount-
ainous region and on the margin of the equatorial zone, are
among the most favourable examples. " On each side of the
road great trees towered up, carrying their crowns out of
sight amongst a canopy of foliage, and with lianas hanging
from nearly every bough, and passing from tree to tree,
entangling the giants in a great network of coiling cables.
Sometimes a tree appears covered with beautiful flowers
which do not belong to it but to one of the lianas that twines
through its branches and sends down great rope-like stems to
the ground. Climbing ferns and vanilla cling to the trunks,
and a thousand epiphytes perch themselves on the branches.
Amongst these are large arums that send down long aerial
roots, tough and strong, and universally used instead of
cordage by the natives. Amongst the undergrowth several
small species of palms, varying in height from two to fifteen
feet, are common ; and now and then magnificent tree ferns
sending off their feathery crowns twenty feet from the ground
delight the sight by their graceful elegance. Great broad-
leaved heliconias, leathery melastomae, and succulent-stemmed,
lop-sided, leaved, and flesh-coloured begonias are abundant,
and typical of tropical American forests ; but not less so are
the cecropia trees, with their white stems and large palmated

266 TROPICAL NATURE

leaves standing up like great candelabra. Sometimes the
ground is carpeted with large flowers, yellow, pink, or white,
that have fallen from some invisible tree-top above ; or the air
is filled with a delicious perfume, the source of which one seeks
around in vain, for the flowers that cause it are far overhead
out of sight, lost in the great overshadowing crown of verdure."

Although, as has been shown elsewhere, it may be
doubted whether light directly produces floral colour, there
can be no doubt that it is essential to the growth of vegeta-
tion and to the full development of foliage and of flowers.
In the forests all trees, and shrubs, and creepers struggle
upwards to the light, there to expand their blossoms and
ripen their fruit. Hence, perhaps, the abundance of climbers
which make use of their more sturdy companions to reach
this necessary of vegetable life. Yet even on the upper
surface of the forest, fully exposed to the light and heat of
the tropical sun, there is no special development of coloured
flowers. When from some elevated point you can gaze down
upon an unbroken expanse of woody vegetation, it often
happens that not a single patch of bright colour can be dis-
cerned. At other times, and especially at the beginning of
the dry season, you may behold scattered at wide intervals
over the mottled-green surface a few masses of yellow, white,
pink, or more rarely of blue colour, indicating the position of
handsome flowering trees.

The well-established relation between coloured flowers
and the need of insects to fertilise them may perhaps be con-
nected with the comparative scarcity of the former in the
equatorial forests. The various forms of life are linked to-
gether in such mutual dependence that no one can inordi-
nately increase without bringing about a corresponding increase
or diminution of other forms. The insects which are best
adapted to fertilise flowers cannot probably increase much
beyond definite limits, because in doing so they would lead to
a corresponding increase of insectivorous birds and other
animals which would keep them down. The chief fertilisers
— bees and butterflies — have enemies at every stage of their
growth, from the egg to the perfect insect, and their numbers
are, therefore, limited by causes quite independent of the
supply of vegetable food. It may, therefore, be the case that

ii EQUATORIAL VEGETATION 267

the numbers of suitable insects are totally inadequate to the
fertilisation of the countless millions of forest trees over such
vast areas as the equatorial zone presents, and that, in con-
sequence, a large proportion of the species have become
adapted either for self-fertilisation, or for cross-fertilisation by
the agency of the wind. Were there not some such limita-
tion as this, we should expect that the continued struggle for
existence among the plants of the tropical forests would have
led to the acquisition, by a much larger proportion of them,
of so valuable a character as bright -coloured flowers, this
being almost a necessary preliminary to a participation in the
benefits which have been proved to arise from cross-fertilisa-
tion by insect agency.

Concluding Remarks on Tropical Vegetation
In concluding this general sketch of the aspects of tropical
vegetation, we will attempt briefly to summarise its main
features. The primeval forests of the equatorial zone are
grand and overwhelming by their vastness, and by the display
of a force of development and vigour of growth rarely or
never witnessed in temperate climates. Among their best
distinguishing features are the variety of forms and species
which everywhere meet and grow side by side, and the extent
to which parasites, epiphytes, and creepers fill up every avail-
able station with peculiar modes of life. If the traveller
notices a particular species and wishes to find more like it, he
may often turn his eyes in vain in every direction. Trees of
varied forms, dimensions, and colours are around him, but he
rarely sees any one of them repeated. Time after time he
goes towards a tree which looks like the one he seeks, but
a closer examination proves it to be distinct. He may at
length, perhaps, meet with a second specimen half a mile off,
or may fail altogether, till on another occasion he stumbles
on one by accident.

The absence of the gregarious or social habit, so general in
the forests of extra-tropical countries, is probably dependent
on the extreme equability and permanence of the climate.
Atmospheric conditions are much more important to the
growth of plants than any others. Their severest struggle
for existence is against climate. As we approach towards

TROPICAL NATURE

regions of polar cold or desert aridity the variety of groups
and species regularly diminishes ; more and more are unable
to sustain the extreme climatal conditions, till at last we find
only a few specially organised forms which are able to main-
tain their existence. In the extreme north, pine or birch
trees — in the desert, a few palms and prickly shrubs or aro-
matic herbs — alone survive. In the equable equatorial zone
there is no such struggle against climate. Every form of
vegetation has become alike adapted to its genial heat and
ample moisture, which has probably changed little even
throughout geological periods ; and the never ceasing struggle
for existence between the various species in the same area has
resulted in a nice balance of organic forces, which gives the
advantage, now to one, now to another species, and prevents
any one type of vegetation from monopolising territory to
the exclusion of the rest. The same general causes have led
to the filling up of every place in nature with some specially
adapted form. Thus we find a forest of smaller trees adapted
to grow in the shade of greater trees. Thus we find every
tree supporting numerous other forms of vegetation, and some
so crowded with epiphytes of various kinds that their forks
and horizontal branches are veritable gardens. Creeping
ferns and arums run up the smoothest trunks ; an immense
variety of climbers hang in tangled masses from the branches
and mount over the highest tree -tops. Orchids, bromelias,
arums, and ferns grow from every boss and crevice, and cover
the fallen and decaying trunks with a graceful drapery.
Even these parasites have their own parasitical growth, their
leaves often supporting an abundance of minute creeping
mosses and hepaticae. But the uniformity of climate which
has led to this rich luxuriance and endless variety of vegetation
is also the cause of a monotony that in time becomes oppress-
ive. To quote the words of Mr. Belt : " Unknown are the
autumn tints, the bright browns and yellows of English woods ;
much less the crimsons, purples, and yellows of Canada, where
the dying foliage rivals, nay excels, the expiring dolphin in
splendour. Unknown the cold sleep of winter ; unknown the
lovely awakening of vegetation at the first gentle touch of
spring. A ceaseless round of ever-active life weaves the
fairest scenery of the tropics into one monotonous whole, of

EQUATORIAL VEGETATION

which the component parts exhibit in detail untold variety
and beauty." l

To the student of nature the vegetation of the tropics will
ever be of surpassing interest, whether for the variety of
forms and structures which it presents, for the boundless
energy with which the life of plants is therein manifested, or
for the help which it gives us in our search after the laws
which have determined the production of such infinitely
varied organisms. When, for the first time, the traveller
wanders in these primeval forests, he can scarcely fail to
experience sensations of awe, akin to those excited by the
trackless ocean or the alpine snowfields. There is a vastness,
a solemnity, a gloom, a sense of solitude and of human
insignificance, which for a time overwhelm him ; and it is only
when the novelty of these feelings have passed away that he
is able to turn his attention to the separate constituents that
combine to produce these emotions, and examine the varied
and beautiful forms of life which, in inexhaustible profusion,
are spread around him.

1 The Naturalist in Nicaragua, p. 56.

Ill

ANIMAL LIFE IN THE TROPICAL FORESTS

Difficulties of the Subject— General Aspect of the Animal Life of Equatorial
Forests — Diurnal Lepidoptera or Butterflies — Peculiar Habits of Tro-
pical Butterflies — Ants, Wasps, and Bees — Ants — Special Relations
between Ants and Vegetation — Wasps and Bees — Orthoptera and
other Insects — Beetles — Wingless Insects — General Observations on
Tropical Insects — Birds : Parrots — Pigeons — Picarise — Cuckoos — Tro-
gons, Barbets, Toucans, and Hornbills — Passeres — Reptiles and
Amphibia : Lizards — Snakes — Frogs and Toads — Mammalia :
Monkeys — Bats — Summary of the Aspects of Animal Life in the
Tropics.

THE attempt to give some account of the general aspects of
animal life in the equatorial zone presents far greater diffi-
culties than in the case of plants. On the one hand, animals
rarely play any important part in scenery, and their entire
absence may pass quite unnoticed ; while the abundance,
variety, and character of the vegetation are among those
essential features that attract every eye. On the other hand,
so many of the more important and characteristic types of
animal life are restricted to one only out of the three great
divisions of equatorial land, that they can hardly be claimed
as characteristically tropical ; while the more extensive zoolog-
ical groups which have a wide range in the tropics and do
not equally abound in the temperate zones, are few in number,
and often include such a diversity of forms, structures, and
habits as to render any typical characterisation of them
impossible. We must then, in the first place, suppose that
our traveller is on the look-out for all signs of animal life ;
and that, possessing a general acquaintance as an out-door
observer with the animals of our own country, he carefully

in ANIMAL LIFE IN THE TROPICAL FORESTS 271

notes those points in which the forests of the equatorial zone
offer different phenomena. Here, as in the case of plants, we
exclude all zoological science, classifications, and nomenclature,
except in as far as it is necessary for a clear understanding
of the several groups of animals referred to. We shall there-
fore follow no systematic order in our notes, except that
which would naturally arise from the abundance or prominence
of the objects themselves. We further suppose our traveller
to have no prepossessions, and to have no favourite group, in
the search after which he passes by other objects which, in
view of their frequent occurrence in the landscape, are really
more important.

General Aspect of the Animal Life of Equatorial Forests
Perhaps the most general impression produced by a first
acquaintance with the equatorial forests is the comparative
absence of animal life. Beast, bird, and insect alike require
looking for, and it very often happens that we look for them
in vain. On this subject Mr. Bates, describing one of his
early excursions into the primeval forests of the Amazon
valley, remarks as follows : " We were disappointed in not
meeting with any of the larger animals of the forest. There
was no tumultuous movement or sound of life. We did not
see or hear monkeys, and no tapir or jaguar crossed our path.
Birds also appeared to be exceedingly scarce." Again : " I
afterwards saw reason to modify my opinion, founded on first
impressions, with regard to the amount and variety of animal
life in this and other parts of the Amazonian forests. There
is, in fact, a great variety of mammals, birds, and reptiles, but
they are widely scattered and all excessively shy of man. The
region is so extensive and uniform in the forest clothing of its
surface, that it is only at long intervals that animals are seen
in abundance, where some particular spot is found which is
more attractive than others. Brazil, moreover, is throughout
poor in terrestrial mammals, and the species are of small size ;
they do not, therefore, form a conspicuous feature in the
forests. The huntsman would be disappointed who expected
to find here flocks of animals similar to the buffalo-herds of
North America, or the swarms of antelopes and herds of
ponderous pachyderms of Southern Africa. We often read

272 TROPICAL NATURE

in books of travel of the silence and gloom of the Brazilian
forests. They are realities, and the impression deepens on a
longer acquaintance. The few sounds of birds are of that
pensive and mysterious character which intensifies the feeling
of solitude rather than imparts a sense of life and cheerfulness.
Sometimes in the midst of the stillness a sudden yell or scream
will startle one ; this comes from some defenceless fruit-eating
animal which is pounced upon by a tiger-cat or a boa-con-
strictor. Morning and evening the howling monkeys make a
most fearful and harrowing noise, under which it is difficult
to keep up one's buoyancy of spirit. The feeling of inhos-
pitable wildness which the forest is calculated to inspire is
increased tenfold under this fearful uproar. Often, even in
the still mid-day hours, a sudden crash will be heard resound-
ing afar through the wilderness, as some great bough or entire
tree falls to the ground." With a few verbal alterations these
remarks will apply equally to the primeval forests of the
Malay Archipelago; and it is probable that those of West
Africa offer no important differences in this respect. There
is, nevertheless, one form of life which is very rarely absent
in the more luxuriant parts of the tropics, and which is more
often so abundant as to form a decided feature in the scene.
It is therefore the group which best characterises the equa-
torial zone, and should form the starting-point for our review.
This group is that of the

Diurnal Lepidoptera or Butterflies

Wherever in the equatorial zone a considerable extent of
the primeval forest remains, the observer can hardly fail to be
struck by the abundance and the conspicuous beauty of the
butterflies. Not only are they abundant in individuals, but
their large size, their elegant forms, their rich and varied
colours, and the number of distinct species almost everywhere
to be met with, are equally remarkable. In many localities
near the northern or southern tropics they are perhaps equally
abundant, but these spots are more or less exceptional, whereas
within the equatorial zone, and with the limitations above
stated, butterflies form one of the most constant and most
conspicuous displays of animal life. They abound most in
old and tolerably open roads and pathways through the forest,

in ANIMAL LIFE IN THE TROPICAL FORESTS 273

but they are also very plentiful in old settlements in which
fruit-trees and shrubbery offer suitable haunts. In the vicinity
of such old towns as Malacca and Amboyna in the East, and
of Para and Rio de Janeiro in the West, they are especially
abundant, and comprise some of the handsomest and most
remarkable species in the whole group. Their aspect is
altogether different from that presented by the butterflies of
Europe and of most temperate countries. A considerable
proportion of the species are very large, six to eight inches
across the wings being not uncommon among the Papilionidse
and Morphidse, while several species are even larger. This
great expanse of wings is accompanied by a slow flight ; and,
as they usually keep near the ground and often rest, some-
times with closed and sometimes with expanded wings, these
noble insects really look larger and are much more con-
spicuous objects than the majority of our native birds. The
first sight of the great blue Morphos flapping slowly along in
the forest roads near Para, of the large white-and-black semi-
transparent Ideas floating airily about in the woods near
Malacca, and of the golden -green Ornithopteras sailing on
bird -like wing over the flowering shrubs which adorn the
beach of the K6 and Aru islands, can never be forgotten by
any one with a feeling of admiration for the new and beautiful
in nature. Next to the size, the infinitely varied and dazzling
hues of these insects most attract the observer. Instead of
the sober browns, the plain yellows, and the occasional patches
of red, or blue, or orange that adorn our European species,
we meet with the most intense metallic blues, the purest
satiny greens, the most gorgeous crimsons, not in small spots
but in large masses, relieved by a black border or background.
In others we have contrasted bands of blue and orange, or of
crimson and green, or of silky yellow relieved by velvety
black. In not a few the wings are powdered over with scales
and spangles of metallic green, deepening occasionally into
blue or golden or deep red spots. Others again have spots
and markings as of molten silver or gold, while several have
changeable hues, like shot^silk or richly-coloured opal. The
form of the wings, again, often attracts attention. Tailed
hind-wings occur in almost all the families, but vary much in
character. In some the tails are broadly spoon- shaped, in
T

TROPICAL NATURE

others long and pointed. Many have double or triple tails,
and some of the smaller species have them immensely elon-
gated and often elegantly curled. In some groups the wings
are long and narrow, in others strongly falcate ; and though
many fly with immense rapidity, a large number nutter lazily
along, as if they had no enemies to fear, and therefore no
occasion to hurry.

The number of species of butterflies inhabiting any one
locality is very variable, and is, as a rule, far larger in
America than in the Eastern hemisphere ; but it everywhere
very much surpasses the numbers in the temperate zone. A
few months' assiduous collecting in any of the Malay islands
will produce from 150 to 250 species of butterflies, and thirty
or forty species may be obtained any fine day in good locali-
ties. In the Amazon valley, however, much greater results
may be achieved. A good day's collecting will produce from
forty to seventy species, while in one year at Para about 600
species were obtained. More than 700 species of butterflies
actually inhabit the district immediately around the city of
Para, and this, as far as we yet know, is the richest spot on
the globe for diurnal lepidoptera. At Ega, during four years'
collecting, Mr. Bates obtained 550 species, and these, on the
whole, surpassed those of Para in variety and beauty. Mr.
Bates thus speaks of a favourite locality on the margin of the
lake near Ega : " The number and variety of gaily -tinted
butterflies, sporting about in this grove on sunny days, were
so great that the bright moving flakes of colour gave quite a
character to the physiognomy of the place. It was impossible
to walk far without disturbing flocks of them from the damp
sand at the edge of the water, where they congregated to
imbibe the moisture. They were of almost all colours, sizes,
and shapes ; I noticed here altogether eighty species, belonging
to twenty-two distinct genera. The most abundant, next to
the very common sulphur-yellow and orange-coloured kinds,
were about a dozen species of Eunica, which are of large size
and conspicuous from their liveries of glossy dark blue and
purple. A superbly adorned creature, the Callithea markii,
having wings of a thick texture, coloured sapphire-blue and
orange, was only an occasional visitor. On certain days, when
the weather was very calm, two small gilded species (Sym-

in ANIMAL LIFE IN THE TROPICAL FORESTS 275

machia trochilus and colubris) literally swarmed on the sands,
their glittering wings lying wide open on the flat surface." 1

When we consider that only sixty-four species of butter-
flies have been found in Britain and about 150 in Germany,
many of which are very rare and local, so that these numbers
are the result of the work of hundreds of collectors for a long
series of years, we see at once the immense wealth of the
equatorial zone in this form of life.

Peculiar Habits of Tropical Butterflies

The habits of the butterflies of the tropics offer many curious
points rarely or never observed among those of the temperate
zone. The majority, as with us, are truly diurnal, but there
are some Eastern Morphidse and the entire American family
Brassolidse, which are crecuspular, coming out after sunset
and flitting about the roads till it is nearly dark. Others,
though flying in the daytime, are only found in the gloomiest
recesses of the forest, where a constant twilight may be said
to prevail. The majority of the species fly at a moderate
height (from five to ten feet above the ground), while a few
usually keep higher up and are difficult to capture; but a
large number, especially the Satyridse, many Erycinidse, and
some few Nymphalidae, keep always close to the ground and
usually settle on or among the lowest herbage. As regards
the mode of flight, the extensive and almost exclusively
tropical families of Heliconidse and Danaidse fly very slowly,
with a gentle undulating or floating motion which is almost
peculiar to them. Many of the strong-bodied Nymphalidae
and Hesperidse, on the other hand, have an excessively rapid
flight, darting by so swiftly that the eye cannot follow them,
and in some cases producing a deep sound louder than that of
the humming-birds.

The places they frequent, and their mode of resting,
are various and often remarkable. A considerable number
frequent damp open places, especially river -sides and the
margins of pools, assembling together in flocks of hundreds of
individuals ; but these are almost entirely composed of males,
the females remaining in the forests, where, towards the after-
noon, their partners join them. The majority of butterflies
1 The Naturalist on the Riwr Amazons, 2d ed., p. 331.

276 TROPICAL NATURE

settle upon foliage and on flowers, holding their wings erect
and folded together, though early in the morning, or when
newly emerged from the chrysalis, they often expand them to
the sun. Many, however, have special stations and attitudes.
Some settle always on tree -trunks, usually with the wings
erect, but the Ageronias expand them and always rest with
the head downwards. Many Nymphalidse prefer resting on
the top of a stick ; others choose bushes with dead leaves ;
others settle on rocks or sand or in dry forest paths. Pieces
of decaying animal or vegetable matter are very attractive to
certain species, and if disturbed they will sometimes return to
the same spot day after day. Some Hesperidse, as well as
species of the genera Cyrestis and Symmachia, and a few
others, rest on the ground with their wings fully expanded
and pressed closely to the surface, as if exhibiting themselves
to the greatest advantage. The beautiful little Erycinidse of
South America vary remarkably in their mode of resting.
The majority always rest on the under surface of leaves with
their wings expanded, so that when they settle they suddenly
disappear from sight. Some, however, as the elegant gold-
spotted Helicopis cupido, rest beneath leaves with closed
wings. A few, as the genera Charis and Themone, for
example, sit on the upper side of leaves with their wings
expanded ; while the gorgeously-coloured Erycinas rest with
wings erect and exposed as in the majority of butterflies.
The Hesperidae vary in a somewhat similar manner. All rest
on the upper side of leaves or on the ground, but some close
their wings, others expand them, and a third group keep
the upper pair of wings raised while the hind wings are
expanded, a habit found in some of our European species.
Many of the Lycsenidse, especially the Theclas, have the
curious habit, while sitting with their wings erect, of
moving the lower pair over each other in opposite directions,
giving them the strange appearance of eccentrically revolving
discs.

The great majority of butterflies disappear at night, rest-
ing concealed amid foliage, or on sticks or trunks, or in such
places as harmonise with their colours and markings ; but the
gaily-coloured Heliconidaa and Daniadae seek no such conceal-
ment, but rest at night hanging at the ends of slender twigs

in ANIMAL LIFE IN THE TROPICAL FORESTS 277

or upon fully exposed leaves. Being uneatable they have no
enemies and need no concealment. Day-flying moths of
brilliant or conspicuous colours are also comparatively abund-
ant in the tropical forests. Most magnificent of all are the
Uranias, whose long -tailed green -and -gold powdered wings
resemble those of true swallow -tailed butterflies. Many
Agaristidae of the East are hardly inferior in splendour, while
hosts of beautiful clearwings and ^Egeriidae add greatly to
the insect beauty of the equatorial zone.

The wonderful examples afforded by tropical butterflies of
the phenomena of sexual and local variation, of protective
modifications, and of mimicry, have been fully discussed
elsewhere. For the study of the laws of variation in all its
forms, these beautiful creatures are unsurpassed by any class
of animals, both on account of their great abundance, and the
assiduity with which they have been collected and studied.
Perhaps no group exhibits the distinctions of species and
genera with such precision and distinctness, due, as Mr. Bates
has well observed, to the fact that all the superficial signs of
change in the organisation are exaggerated, by their affecting
the size, shape, and colour of the wings, and the distribution
of the ribs or veins which form their framework. The minute
scales or feathers with which the wings are clothed are coloured
in regular patterns, which vary in accordance with the slightest
change in the conditions to which the species are exposed.
These scales are sometimes absent in spots or patches, and
sometimes over the greater part of the wings, which then
become transparent, relieved only by the dark veins and by
delicate shades or small spots of vivid colour, producing a
special form of delicate beauty characteristic of many South
American butterflies. The following remark by Mr. Bates
will fitly conclude our sketch of these lovely insects. "It
may be said, therefore, that on these expanded membranes
Nature writes, as on a tablet, the story of the modifications of
species, so truly do all the changes of the organisation register
themselves thereon. And as the laws of Nature must be the
same for all beings, the conclusions furnished by this group
of insects must be applicable to the whole organic world ;
therefore the study of butterflies — creatures selected as the
types of airiness and frivolity — instead of being despised, will

278 TROPICAL NATURE

some day be valued as one of the most important branches of
biological science." l

Next after the butterflies in importance, as giving an air
of life and interest to tropical nature, we must place the birds ;
but to avoid unnecessary passage, to and fro, among unrelated
groups, it will be best to follow on with a sketch of such
other groups of insects as from their numbers, variety, habits,
or other important features, attract the attention of the
traveller from colder climates. We begin then with a group
which, owing to their small size and obscure colours, would
attract little attention, but which nevertheless, by the
universality of their presence, their curious habits, and the
annoyance they often cause to man, are sure to force them-
selves upon the attention of every one who visits the tropics.

Ants, Wasps, and Bees

The hymenopterous insects of the tropics are, next to the
butterflies, those which come most prominently before the
traveller, as they love the sunshine, frequent gardens, houses,
and roadways as well as the forest shades, never seek conceal-
ment, and are many of them remarkable for their size or
form, or are adorned with beautiful colours and conspicuous
markings. Although ants are, perhaps, on the whole, the
smallest and the least attractive in appearance of all tropical
insects, yet, owing to their being excessively abundant and
almost omnipresent, as well as on account of their curious
habits and the necessity of being ever on the watch against
their destructive powers, they deserve our first notice.

Ants are found everywhere. They abound in houses,
some living underground, others in the thatched roofs, on the
under surface of which they make their nests, while covered
ways of earth are often constructed upon the posts and doors.
In the forests they live on the ground, under leaves, on the
branches of trees, or under rotten bark ; while others actually
dwell in living plants, which seem to be specially modified so
as to accommodate them. Some sting severely, others only
bite ; some are quite harmless, others exceedingly destructive.
The number of different kinds is very great. In India and
the Malay Archipelago nearly 500 different species have been
1 Bates, The Naturalist on the River Amazons, 2d ed., p. 413.

in ANIMAL LIFE IN THE TROPICAL FORESTS 279

found, and other tropical countries are no doubt equally rich.
I will first give some account of the various species observed
in the Malay islands, and afterwards describe some of the
more interesting South American groups, which have been
so carefully observed by Mr. Bates on the Amazons and by
Mr. Belt in Nicaragua.

Among the very commonest ants in all parts of the world
are the species of the family Formicidse, which do not sting,
and are most of them quite harmless. Some make delicate
papery nests, others live under stones or among grass.
Several of them accompany Aphides to feed upon the sweet
secretions from their bodies. They vary in size from the
large Formica gigas, more than an inch long, to minute
species so small as to be hardly visible. Those of the genus
Polyrachis, which are plentiful in all Eastern forests, are
remarkable for the extraordinary hooks and spines with which
their bodies are armed, and they are also in many cases
beautifully sculptured or furrowed. They are not numerous
individually, and are almost all arboreal, crawling about bark
and foliage. One species has processes on its back just like
fish-hooks, others are armed with long, straight spines. They
generally form papery nests on leaves, and when disturbed
they rush out and strike their bodies against the nest so as to
produce a loud rattling noise j but the nest of every species
differs from those of all others either in size, shape, or position.
As they all live in rather small communities in exposed
situations, are not very active, and are rather large and con-
spicuous, they must be very much exposed to the attacks of
insectivorous birds and other creatures, and having no sting
or powerful jaws with which to defend themselves, they would
be liable to extermination without some special protection.
This protection they no doubt obtain by their hard smooth
bodies, and by the curious hooks, spines, points, and bristles
with which they are armed, which must render them unpalat-
able morsels, very liable to stick in the jaws or throats of their
captors.

A curious and very common species in the Malay islands
is the green ant ((Ecophylla smaragdina), a rather large, long-
legged, active, and intelligent-looking creature, which lives in
large nests formed by gluing together the edges of leaves,

TROPICAL NATURE

especially of Zingiberaceous plants. When the nest is touched
a number of the ants rush out, apparently in a great rage,
stand erect, and make a loud rattling noise by tapping against
the leaves. This no doubt frightens away many enemies, and
is their only protection ; for though they attempt to bite, their
jaws are blunt and feeble, and they do not cause any pain.

Coming now to the stinging groups, we have first a number
of solitary ants of the great genus Odontomachus, which are
seen wandering about the forest and are conspicuous by their
enormously long and slender hooked jaws. These are not
powerful, but serve admirably to hold on by while they sting,
which they do pretty severely. The Poneridse are another group
of large-sized ants which sting acutely. They are very varied
in species but are not abundant individually. The Ponera
clavata of Guiana is one of the worst stinging ants known.
It is a large species, frequenting the forests on the ground, and
is much dreaded by the natives, as its sting produces intense
pain and illness. I was myself stung by this or an allied species
when walking barefoot in the forest on the Upper Rio Negro.
It caused such pain and swelling of the leg that I had some
difficulty in reaching home, and was confined to my room for two
days. Sir Robert Schomburgh suffered more ; for he fainted
with the pain, and had an attack of fever in consequence.

We now come to the Myrmecidae, which may be called
the destroying ants, from their immense abundance and de-
structive propensities. Many of them sting most acutely,
causing a pain like that of a sudden burn, whence they are
often called " fire-ants." They often swarm in houses and
devour everything eatable. Isolation by water is the only
security, and even this does not always succeed, as a little
dust on the surface will enable the smaller species to get
across. Oil is, however, an effectual protection, and after
many losses of valuable insect specimens, for which ants have
a special affection, I always used it. One species of this
group, a small black Crematogaster, took possession of my
house in New Guinea, building nests in the roof and making
covered ways down the posts and across the floor. They also
occupied the setting boards I used for pinning out my butter-
flies, filling up the grooves with cells and storing them with
small spiders. They were in constant motion, running over

in ANIMAL LIFE IN THE TROPICAL FORESTS 281

my table, in my bed, and all over my body. Luckily, they
were diurnal, so that on sweeping out my bed at night I
could get on pretty well ; but during the day I could always
feel some of them running over my body, and every now and
then one would give me a sting so sharp as to make me jump
and search instantly for the offender, who was usually found
holding on tight with his jaws and thrusting in his sting with
all his might. Another genus, Pheidole, consists of forest
ants, living under rotten bark or in the ground, and very
voracious. They are brown or blackish, and are remarkable
for their great variety of size and form in the same species,
the largest having enormous heads many times larger than
their bodies, and being at least a hundred times as bulky as
the smallest individuals. These great-headed ants are very
sluggish and incapable of keeping up with the more active
small workers, which often surround and drag them along as
if they were wounded soldiers. It is difficult to see what use
they can be in the colony, unless, as Mr. Bates suggests, they
are mere baits to be attacked by insect-eating birds, and thus
save their more useful companions. These ants devour grubs,
white ants, and other soft and helpless insects, and seem to
take the place of the foraging ants of America and driver
ants of Africa, though they are far less numerous and less
destructive. An allied genus, Solenopsis, consists of red ants,
which, in the Moluccas, frequent houses, and are a most
terrible pest. They form colonies underground, and work
their way up through the floors, devouring everything eat-
able. Their sting is excessively painful, and some of the
species are hence called fire-ants. When a house is infested
by them, all the tables and boxes must be supported on
blocks of wood or stone placed in dishes of water, as even
clothes njot newly washed are attractive to them ; and woe to
the poor fellow who puts on garments in the folds of which
a dozen of these ants are lodged. It is very difficult to
preserve bird skins or other specimens of natural history
where these ants abound, as they gnaw away the skin round
the eyes and the base of the bill, and if a specimen is laid
down for even half an hour in an unprotected place it will
be ruined. I remember once entering a native house to rest
and eat my lunch ; and having a large tin collecting-box full

TROPICAL NATURE

of rare butterflies and other insects, I laid it down on the
bench by my side. On leaving the house I noticed some ants
on it, and on opening the box found only a mass of detached
wings and bodies, the latter in process of being devoured by
hundreds of fire-ants.

The celebrated Sauba ant of America (CEcodoma cepha-
lotes) is allied to the preceding, but is even more destructive,
though it seems to confine itself to vegetable products. It
forms extensive underground galleries, and the earth brought
up is deposited on the surface, forming huge mounds some-
times thirty or forty yards in circumference and from one
to three feet high. On first seeing these vast deposits of
red or yellow earth in the woods near Para, it was hardly
possible to believe they were not the work of man, or at
least of some large burrowing animal. In these underground
caves the ants store up large quantities of leaves, which they
obtain from living trees. They gnaw out circular pieces and
carry them away along regular paths a few inches wide,
forming a stream of apparently animated leaves. The great
extent of the subterranean workings of these ants is no doubt
due in part to their permanence in one spot, so that when
portions of the galleries fall in or are otherwise rendered
useless, they are extended in another direction. When in
the island of Mara jo, near Para, I noticed a path along which
a stream of Saiibas were carrying leaves from a neighbouring
thicket; and a relation of the proprietor assured me that
he had known that identical path to be in constant use by
the ants for twenty years. Thus we can account for the
fact mentioned by Mr. Bates, that the underground galleries
were traced by smoke for a distance of seventy yards in the
Botanic Gardens at Para ; and for the still more extraordinary
fact related by the Eev. Hamlet Clark, that an allied species
in Eio de Janeiro has excavated a tunnel under the bed of
the river Parahyba, where it is about a quarter of a mile wide !
These ants seem to prefer introduced to native trees ; and young
plantations of orange, coffee, or mango trees are sometimes
destroyed by them, so that where they abound cultivation of
any kind becomes almost impossible. Mr. Belt ingeniously
accounts for this preference by supposing that for ages there
has been a kind of struggle going on between the trees

in ANIMAL LIFE IN THE TROPICAL FORESTS 283

and the ants ; those varieties of trees which were in any
way distasteful or unsuitable escaping destruction, while the
ants were becoming slowly adapted to attack new trees.
Thus in time the great majority of native trees have acquired
some protection against the ants, while foreign trees, not
having been so modified, are more likely to be suitable for
their purposes. Mr. Belt carried on war against them for
four years to protect his garden in Nicaragua, and found
that carbolic acid and corrosive sublimate were most effectual
in destroying or driving them away.

The use to which the ants put the immense quantities of
leaves they carry away has been a great puzzle, and is, per-
haps, not yet quite understood. Mr. Bates found that the
Amazon species used them to thatch the domes of earth cover-
ing the entrances to their subterranean galleries, the pieces of
leaf being carefully covered and kept in position by a thin layer
of grains of earth. In Nicaragua Mr. Belt found the under-
ground cells full of a brown flocculent matter, which he con-
siders to be the gnawed leaves connected by a delicate fungus
which ramifies through the mass and which serves as food for
the larvae ; and he believes that the leaves are really gathered
as manure-heaps to favour the growth of this fungus !

When they enter houses, which they often do at night,
the Saiibas are very destructive. Once, when travelling on
the Rio Negro, I had bought about a peck of rice, which was
tied up in a large cotton handkerchief and placed on a bench
in a native house where we were spending the night. The
next morning we found about half the rice on the floor, the
remainder having been carried away by the ants ; and the
empty handkerchief was still on the bench, but with hundreds
of neat cuts in it reducing it to a kind of sieve.1

The foraging ants of the genus Eciton are another remark-
able group, especially abundant in the equatorial forests of
America. They are true hunters, and seem to be continually
roaming about the forests in great bands in search of insect
prey. They especially devour maggots, caterpillars, white
ants, cockroaches, and other soft insects ; and their bands

1 For a full and most interesting description of the habits and instincts of
this ant, see Bates' Naturalist on the River Amazons, 2d ed., pp. 11-18 ;
and Belt's Naturalist in Nicaragua, pp. 71-84.

TROPICAL NATURE

are always accompanied by flocks of insectivorous birds, who
prey upon the winged insects that are continually trying to
escape from the ants. They even attack wasps' nests, which
they cut to pieces and then drag out the larvae. They bite
and sting severely, and the traveller who accidentally steps
into a horde of them will soon be overrun, and must make
his escape as quickly as possible. They do not confine them-
selves to the ground, but swarm up bushes and low trees,
hunting every branch, and clearing them of all insect life.
Sometimes a band will enter a house, like the driver ants in
Africa, and clear it of cockroaches, spiders, centipedes, and
other insects. They seem to have no permanent abode, and to
be ever wandering about in search of prey, but they make
temporary habitations in hollow trees or other suitable places.
Perhaps the most extraordinary of all ants are the blind
species of Eciton discovered by Mr. Bates, which construct a
covered way or tunnel as they march along. On coming
near a rotten log, or any other favourable hunting ground,
they pour into all its crevices in search of booty, their
covered way serving as a protection to retire to in case of
danger. These creatures, of which two species are known,
are absolutely without eyes ; and it seems almost impossible
to imagine that the loss of so important a sense-organ can be
otherwise than injurious to them. Yet on the theory of
natural selection the successive variations by which the eyes
were reduced and ultimately lost must all have been useful.
It is true they do manage to exist without eyes ; but that is
probably because, as sight became more and more imperfect,
new instincts or new protective modifications were developed
to supply its place, and this does not in any way account for
so widespread and invaluable a sense having become per-
manently lost, in creatures which still roam about and hunt
for prey very much as do their fellows who can see.

Special Relations between Ants and Vegetation
Attention has recently been called to the very remarkable
relations existing between some trees and shrubs and the ants
which dwell upon them. In the Malay islands are several
curious shrubs belonging to the Cinchonacese, which grow
parasitically on other trees, and whose swollen stems are

in ANIMAL LIFE IN THE TROPICAL FORESTS 285

veritable ants' nests. When very young the stems are like
small, irregular, prickly tubers, in the hollows of which ants
establish themselves ; and these in time grow into irregular
masses the size of large gourds, completely honeycombed with
the cells of ants.1 In America there are some analogous cases
occurring in several families of plants, one of the most
remarkable being that of certain Melastomas which have a
kind of pouch formed by an enlargement of the petiole of
the leaf, and which is inhabited by a colony of small ants.
The hollow stems of the Cecropias (curious trees with pale
bark and large palmate leaves which are white beneath) are
always tenanted by ants, which make small entrance holes
through the bark ; but here there seems no special adaptation
to the wants of the insect. In a species of Acacia observed
by Mr. Belt, the thorns are immensely large and hollow, and
are always tenanted by ants. When young these thorns are
soft and full of a sweetish pulpy substance, so that when the
ants first take possession they find a store of food in their
house. Afterwards they find a special provision of honey-
glands on the leaf -stalks, and also small yellow fruit- like
bodies which are eaten by the ants ; and this supply of food
permanently attaches them to the plant. Mr. Belt believes,
after much careful observation, that these ants protect the
plant they live on from leaf-eating insects, especially from the
destructive Saiiba ants, — that they are in fact a standing
army kept for the protection of the plant ! This view is
supported by the fact that other plants — Passion-flowers for
example — have honey-secreting glands on the young leaves
and on the sepals of the flower-buds which constantly attract
a small black ant. If this view is correct, we see that the
need of escaping from the destructive attacks of the leaf-
cutting ants has led to strange modifications in many plants.
Those in which the foliage was especially attractive to these
enemies were soon weeded out unless variations occurred which
tended to preserve them. Hence the curious phenomenon of
insects specially attracted to certain plants to protect them
from other insects ; and the existence of the destructive leaf-

1 These form two genera, Myrmecodia and Hydnophytum. For descrip-
tion and figures see Mr. H. 0. Forbes' Naturalist's Wanderings in the Eastern
Archipelago, p. 79.

286 TROPICAL NATURE

cutting ant in America will thus explain why these specially
modified plants are so much more abundant there than in the
Old World, where no ants with equally destructive habits
appear to exist.

Wasps and Bees

These insects are excessively numerous in the tropics, and,
from their large size, their brilliant colours, and their great
activity, they are sure to attract attention. Handsomest of
all, perhaps, are the Scoliadae, whose large and rather broad
hairy bodies, often two inches long, are richly banded with
yellow or orange. The Pompilidae comprise an immense
number of large and handsome insects, with rich blue-black
bodies and wings and exceedingly long legs. They may often
be seen in the forests dragging along large spiders, beetles, or
other insects they have captured. Some of the smaller
species enter houses and build earthen cells, which they store
with small green spiders rendered torpid by stinging, to feed
the larvae. The Eumenidae are beautiful wasps with very
long pedunculated bodies, which build papery cones covering
a few cells in which the eggs are deposited. Among the bees
the Xylocopas, or wood -boring bees, are remarkable. They
resemble large humble-bees, but have broad, flat, shining
bodies, either black or banded with blue ; and they often bore
large cylindrical holes in the posts of houses. True honey-
bees are chiefly remarkable in the East for their large semi-
circular combs suspended from the branches of the loftiest
trees without any covering. From these exposed nests large
quantities of wax and honey are obtained, while the larvae
afford a rich feast to the natives of Borneo, Timor, and other
islands where bees abound. They are very pugnacious, and,
when disturbed will follow the intruders for miles, stinging
severely.

Orthoptera and other Insects

Next to the butterflies and ants, the insects that are most
likely to attract the attention of the stranger in the tropics
are the various forms of Mantidse and Phasmidae, some of
which are remarkable for their strange attitudes and bright
colours ; while others are among the most singular of known
insects, owing to their resemblance to sticks and leaves. The

in ANIMAL LIFE IN THE TROPICAL FORESTS 287

Mantidse — usually called " praying insects," from their habit of
sitting with their long fore-feet held up as if in prayer — are
really tigers among insects, lying in wait for their prey, which
they seize with their powerful serrated fore-feet. They are
usually so coloured as to resemble the foliage among which
they live, and as they sit quite motionless, they are not easily
perceived.

The Phasmidse are perfectly inoffensive leaf-eating insects of
very varied forms ; some being broad and leaf-like, while others
are long and cylindrical, so as to resemble sticks, whence they
are often called walking-stick insects. The imitative resem-
blance of some of these insects to the plants on which they
live is marvellous. The true leaf-insects of the East, forming
the genus Phyllium, are the size of a moderate leaf, which their
large wing-covers and the dilated margins of the head, thorax,
and legs cause them exactly to resemble. The veining of the
wings and their green tint exactly correspond to that of the
leaves of their food-plant ; and as they rest motionless during
the day, only feeding at night, they the more easily escape
detection. In Java they are often kept alive on a branch of
the guava tree ; and it is a common thing for a stranger, when
asked to look at this curious insect, to inquire where it is, and
on being told that it is close under his eyes, to maintain that
there is no insect at all, but only a branch with green leaves.

The larger wingless stick-insects are often eight inches to
a foot long. They are abundant in the Moluccas ; hanging on
the shrubs that line the forest-paths ; and they resemble sticks
so exactly, in colour, in the small rugosities of the bark, in the
knots and small branches, imitated by the joints of the legs
which are either pressed close to the body, or stuck out at
random, that it is absolutely impossible, by the eye alone, to
distinguish the real dead twigs which fall down from the trees
overhead, from the living insects. The writer has often looked
at them in doubt, and has been obliged to use the sense of
touch to determine the point. Some are small and slender
like the most delicate twigs ; others again have wings, and it
is curious that these are often beautifully coloured, generally
bright pink, sometimes yellow, and sometimes finely banded
with black ; but when at rest the wings fold up so as to be
completely concealed under the narrow wing-covers, and the

TROPICAL NATURE

whole insect is then green or brown, and almost invisible
among the twigs or foliage. To increase the resemblance to
vegetation, some of these Phasmas have small green processes
in various parts of their bodies looking exactly like moss.
These inhabit damp forests both in the Malay islands and in
America, and they are so marvellously like moss-grown twigs
that the closest examination is needed to satisfy oneself that
it is really a living insect we are looking at.

Many of the locusts are equally well-disguised, some re-
sembling green leaves, others those that are brown and dead ;
and the latter often have small transparent spots on the wings,
looking like holes eaten through them. That these disguises
deceive their natural enemies is certain, for otherwise the
Phasmidae would soon be exterminated. They are large and
sluggish, and very soft and succulent ; they have no means of
defence or of flight, and they are eagerly devoured by numbers
of birds, especially by the numerous cuckoo tribe, whose
stomachs are often full of th'em ; yet numbers of them escape
destruction, and this can only be due to their vegetable
disguises. Mr. Belt records a curious instance of the actual
operation of this kind of defence in a leaf -like locust, which
remained perfectly quiescent in the midst of a host of insecti-
vorous ants, which ran over it without finding out that it was an
insect and not a leaf ! It might have flown away from them,
but it would then instantly have fallen a prey to the numerous
birds which always accompany these roaming hordes of ants
to feed upon the insects that endeavour to escape. Far more
conspicuous than any of these imitative species are the large
locusts, with rich crimson or blue -and -black spotted wings.
Some of these are nearly a foot in expanse of wings ; they
fly by day, and their strong spiny legs probably serve as a
protection against all the smaller birds. They cannot be
said to be common ; but when met with they fully satisfy our
notions as to the large size and gorgeous colours of tropical
insects.1

Beetles

Considering the enormous numbers and endless variety
of the beetle tribe that are known to inhabit the tropics, they

1 It has now been ascertained that these conspicuously coloured locusts are
protected by inedibility. See Darwinism, p. 267.

in ANIMAL LIFE IN THE TROPICAL FORESTS 289

form by no means so prominent a feature in the animal life
of the equatorial zone as we might expect. Almost every
entomologist is at first disappointed with them. He finds that
they have to be searched for almost as much as at home,
while those of large size (except one or two very common
species) are rarely met with. The groups which most attract
attention, from their size and beauty, are the Buprestidse and
the Longicorns. The former are usually smooth insects of an
elongate ovate form, with very short legs and antennae, and
adorned with the most glowing metallic tints. They abound
on fallen tree-trunks and on foliage, in the hottest sunshine,
and are among the most brilliant ornaments of the tropical
forests. Some parts of the temperate zone, especially Aus-
tralia and Chili, abound in Buprestidse which are equally
beautiful ; but the largest species are only found within the
tropics, those of the Malay islands being the largest of all.

The Longicorns are elegantly shaped beetles, usually with
long antennas and legs, varied in form and structure in an
endless variety of ways, and adorned with equally varied
colours, spots, and markings. Some are large and massive
insects three or four inches long, while others are no bigger
than our smaller ants. The majority have sober colours, but
often delicately marbled, veined, or spotted ; while others are
red, or blue, or yellow, or adorned with the richest metallic
tints. Their antennae are sometimes excessively long and
graceful, often adorned with tufts of hair, and sometimes
pectinated. They especially abound where timber trees have
been recently felled in the primeval forests ; and while ex-
tensive clearings are in progress their variety seems endless.
In such a locality in the island of Borneo, nearly 300 different
species were found during one dry season, while the number
obtained during eight years' collecting in the whole Malay
Archipelago was about a thousand species.

Among the beetles that always attract attention in the tropics
are the large, horned Copridse and Dynastidse, corresponding
to our dung-beetles. Some of these are of great size, and
they are occasionally very abundant. The immense horn -like
protuberances on the head and thorax of the males in some of
the species are very extraordinary, and, combined with their
polished or rugose metallic colours, render them perhaps the
u

290 TROPICAL NATURE

most conspicuous of all the beetle tribe. The weevils and
their allies are also very interesting, from their immense
numbers, endless variety, and the extreme beauty of many of
the species. The Anthribidae, which are especially abundant
in the Malay Archipelago, rival the Longicorns in the immense
length of their elegant antennae ; while the diamond beetles of
Brazil, the Eupholi of the Papuan islands, and the Pachy-
rhynchi of the Philippines, are veritable living jewels.

Where a large extent of virgin forest is cut down in the
early part of the dry season, and some hot sunny weather
follows, the abundance and variety of beetles attracted by the
bark and foliage in various stages of drying is amazing. The
air is filled with the hum of their wings. Golden and green
Buprestidae are flying about in every direction, and settling
on the bark in full sunshine. Green and spotted rose-chafers
hum along near the ground ; long -horned Anthribidae are
disturbed at every step ; elegant little Longicorns circle
about the drying foliage, while larger species fly slowly
from branch to branch. Every fallen trunk is full of life.
Strange mottled, and spotted, and rugose Longicorns, endless
Curculios, queer -shaped Brenthidae, velvety brown or steel-
blue Cleridae, brown or yellow or whitish click beetles
(Elaters), and brilliant metallic Carabidae. Close by, in
the adjacent forest, a whole host of new forms are found.
Elegant tiger-beetles, leaf-hunting Carabidae, musk-beetles of
many sorts, scarlet Telephori, and countless Chrysomelas,
Hispas, Coccinellas, with strange Heteromera, and many curious
species which haunt fungi, rotten bark, or decaying leaves.
With such variety and beauty the most ardent entomologist
must be fully satisfied ; and when, every now and then, some
of the giants of the tropics fall in his way — grand Prionidae or
Lamiidae several inches long, a massive golden Buprestis, or a
monster horned Dynastes — he feels that his most exalted
notions of the insect-life of the tropics are at length realised.

Wingless Insects

Passing on to other orders of insects, the hemiptera
dragon -flies and true flies hardly call for special remark.
Among them are to be found a fair proportion of large and
handsome species, but they require much searching after in

in ANIMAL LIFE IN THE TROPICAL FORESTS 291

their special haunts, and seldom attract so much attention as
the groups already referred to. More prominent are the
wingless tribes, such as spiders, scorpions, and centipedes.
The wanderer in the forest often finds the path closed by large
webs almost as strong as silk, inhabited by gorgeous spiders
with bodies nearly two inches long and legs expanding six
inches. Others are remarkable for their hard flat bodies,
terminating in horned processes which are sometimes long,
slender, and curved like a pair of miniature cow's horns.
Hairy terrestrial species of large size are often met with, the
largest belonging to the South American genus Mygale, which
sometimes actually kill birds, a fact which had been stated
by Madame Merian and others, but was discredited till
Mr. Bates succeeded in catching one in the act. The small
jumping spiders are also noticeable from their immense
numbers, variety, and beauty. They frequent foliage and
flowers, running about actively in pursuit of small insects ;
and many of them are so exquisitely coloured as to resemble
jewels rather than spiders. Scorpions and centipedes make
their presence known to every traveller. In the damp
forests of the Malay islands are huge scorpions of a greenish
colour and eight or ten inches long ; while in huts and houses
smaller species lurk under boxes and boards, or secret them-
selves in almost every article not daily examined. Centipedes
of immense size and deadly venom harbour in the thatch of
houses and canoes, and will even ensconce themselves under
pillows and in beds, rendering a thorough examination
necessary before retiring to rest. Yet with moderate pre-
cautions there is little danger from these disgusting insects, as
may be judged by the fact that during twelve years' wander-
ings in American and Malayan forests the author was never
once bitten or stung by them.

General Observations on Tropical Insects
The characteristics of tropical insects that will most attract
the ordinary traveller are, their great numbers, and the
large size and brilliant colours often met with. But a more
extended observation leads to the conclusion that the average
of size is probably but little greater in tropical than in
temperate zones, and that, to make up for a certain proper-

292 TROPICAL NATURE

tion of very large, there is a corresponding increase in the
numbers of very small species. The much greater size reached
by many tropical insects is no doubt due to the fact that the
supply of food is always in excess of their demands in the
larva state, while there is no check from the ever-recurring
cold of winter ; and they are thus able to acquire the dimen-
sions that may be on the whole most advantageous to the race,
unchecked by the annual or periodical scarcities which in less
favoured climates would continually threaten their extinction.
The colours of tropical insects are, probably, on the average
more brilliant than those of temperate countries, and some of
the causes which may have led to this have been discussed in
another part of this volume.1 It is in the tropics that we
find, most largely developed, whole groups of insects which
are unpalatable to almost all insectivorous creatures, and it is
among these that some of the most gorgeous colours prevail.
Others obtain protection in a variety of ways; and the
amount of cover or concealment always afforded by the
luxuriant tropical vegetation is probably a potent agent in
permitting a full development of colour.

BIRDS

Although the number of brilliantly-coloured birds in almost
every part of the tropics is very great, yet they are by no
means conspicuous, and as a rule they can hardly be said to
add much to the general effect of equatorial scenery. The
traveller is almost always disappointed at first with the birds,
as he is with the flowers and the beetles ; and it is only when,
gun in hand, he spends days in the forest, that he finds out
how many beautiful living things are concealed by its dense
foliage and gloomy thickets. A considerable number of the
handsomest tropical birds belong to family groups which are
confined to one continent with its adjacent islands, and we
shall therefore be obliged to deal for the most part with such
large divisions as tribes and orders, by means of which to
define the characteristics of tropical bird-life. We find that
there are three important orders of birds which, though by
no means exclusively tropical, are yet so largely developed
there in proportion to their scarcity in extra-tropical regions,
1 Chapters v. and vi, post. The Colours of Animals and Plants.

in ANIMAL LIFE IN THE TROPICAL FORESTS 293

that, more than any others, they serve to give a special char-
acter to equatorial ornithology. These are the Parrots, the
Pigeons, and the Picariae, to each of which groups we will
devote some attention.

Parrots

The parrots, forming the order Psittaci of naturalists, are
a remarkable group of fruit -eating birds, of such high and
peculiar organisation that they are often considered to stand
at the head of the entire class. They are pre-eminently
characteristic of the intertropical zone, being nowhere absent
within its limits (except from absolutely desert regions), and
they are generally so abundant and so conspicuous as to
occupy among birds the place assigned to butterflies among
insects. A few species range far into the temperate zones.
One reaches Carolina in North America, another the Magellan
Straits in South America ; in Africa they only extend a few
degrees beyond the southern tropic ; in North- Western India
they reach 35° north latitude, but in the Australian region
they range farthest towards the pole, being found not only in
New Zealand, but as far as the Macquarie islands in 54°
south, where the climate is very cold and boisterous, but
sufficiently uniform to supply vegetable food throughout the
year. There is hardly any part of the equatorial zone in
which the traveller will not soon have his attention called to
some members of the parrot tribe. In Brazil the great blue
and yellow or crimson macaws may be seen every evening
wending their way homeward in pairs, almost as commonly
as rooks with us, while innumerable parrots and parraquets
attract attention by their harsh cries when disturbed from
some favourite fruit-tree. In the Moluccas and New Guinea
white cockatoos and gorgeous lories in crimson and blue are
the very commonest of birds.

No group of birds — perhaps no other group of animals —
exhibits within the same limited number of genera and species
so wide a range and such an endless variety of colour. As a
rule, parrots may be termed green birds, the majority of the
species having this colour as the basis of their plumage
relieved by caps, gorgets, bands, and wing-spots of other and
brighter hues. Yet this general green tint sometimes changes

294 TROPICAL NATURE

into light or deep blue, as in some macaws ; into pure yellow
or rich orange, as in some of the American macaw -parrots
(Conurus); into purple, gray, or dove-colour, as in some
American, African, and Indian species ; into the purest crim-
son, as in some of the lories ; into rosy- white and pure white,
as in the cockatoos ; and into a deep purple, ashy, or black,
as in several Papuan, Australian, and Mascarene species.
There is, in fact, hardly a single distinct and definable colour
that cannot be fairly matched among the 400 species of
known parrots. Their habits, too, are such as to bring them
prominently before the eye. They usually feed in flocks ;
they are noisy, and so attract attention ; they love gardens,
orchards, and open sunny places ; they wander about far in
search of food, and towards sunset return homewards in noisy
flocks, or in constant pairs. Their forms and motions are
often beautiful and attractive. The immensely long tails of
the macaws, and the more slender tails of the Indian parra-
quets ; the fine crest of the cockatoos ; the swift flight of
many of the smaller species, and the graceful motions of the
little love-birds and allied forms, together with their affec-
tionate natures, aptitude for domestication, and powers of
mimicry — combine to render them at once the most con-
spicuous and the most attractive of all the specially tropical
forms of bird-life.

The number of species of parrots found in the different
divisions of the tropics is very unequal. Africa is by far the
poorest; since along with Madagascar and the Mascarene
islands, which have many peculiar forms, it scarcely numbers
two dozen species. Asia, along with the Malay islands as far
as Java and Borneo, is also very poor, with about thirty
species. Tropical America is very much richer, possessing
about 140 species, among which are many of the largest and
most beautiful forms. But of all parts of the globe the
tropical islands belonging to the Australian region (from
Celebes eastward), together with the tropical parts of Australia,
are richest in the parrot tribe, possessing more than 150 species,
among which are many of the most remarkable and beautiful
of the entire group. The whole Australian region, whose
extreme limits may be defined by Celebes, the Marquesas, and
the New Zealand group, possesses over 200 species of parrots.

in ANIMAL LIFE IN THE TROPICAL FORESTS 295

These are such common birds in all temperate countries
that it may surprise many .readers to learn that they are
nevertheless a characteristic tropical group. That such is the
case, however, will be evident from the fact that only sixteen
species are known from the whole of the temperate parts of
Europe, Asia, and North America, while about 330 species
inhabit the tropics. Again, the great majority of the species
are found congregated in the equatorial zone, whence they
diminish gradually toward the limits of the tropics, and then
suddenly fall off in the temperate zones. Yet although they
are pre-eminently tropical or even equatorial as a group, they
are not, from our present point of view, of much importance,
because they are so shy and so generally inconspicuous that
in most parts of the tropics an ordinary observer might hardly
be aware of their existence. The remark applies especially to
America and Africa, where they are neither very abundant
nor peculiar ; but in the Eastern hemisphere, and especially
in the Malay Archipelago and Pacific islands, they occur in
such profusion and present such singular forms and brilliant
colours, that they are sure to attract attention. Here we
find the extensive group of fruit -pigeons, which, in their
general green colours adorned with patches and bands of
purple, white, blue, or orange, almost rival the parrot tribe ;
while the golden -green Nicobar pigeon, the great crowned
pigeons of New Guinea as large as turkeys, and the golden-
yellow fruit-dove of the Fijis, can hardly be surpassed for beauty.

Pigeons are especially abundant and varied in tropical
archipelagoes, so that if we take the Malay and Pacific islands,
the Madagascar group, and the Antilles or West Indian
islands, we find that they possess between them more different
kinds of pigeons than all the continental tropics combined.
Yet further, that portion of the Malay Archipelago east of
Borneo, together with the Pacific islands, is exceptionally
rich in pigeons ; and the reason seems to be that monkeys
and all other arboreal mammals that devour eggs and young
birds are entirely absent from this region. Even in South
America pigeons are scarce where monkeys are abundant, and
vice versd, so that here we seem to get a glimpse of one of the

TROPICAL NATURE

curious interactions of animals on each other, by which their
distribution, their habits, and even their colours, may have
been influenced, for the most conspicuous pigeons, whether by
colour or by their crests, are all found in countries where
they have the fewest enemies.

Pwarice

The extensive and heterogeneous series of bird till recently
comprised under this term includes most of the fissirostral
and scansorial groups of the older naturalists. They may be
described as, for the most part, arboreal birds, of a low grade
of organisation, with weak or abnormally developed feet, and
usually less active than the true Passeres or perching birds of
which our warblers, finches, and crows may be taken as the
types. The order Picarise comprises twenty-five families, some
of which are very extensive. All are either wholly or mainly
tropical, only two of the families — the woodpeckers and the
kingfishers — having a few representatives which are per-
manent residents in the temperate regions, while our summer
visitor, the cuckoo, is the sole example in Northern Europe
of one of the most abundant and widespread tropical families
of birds. Only four of the families have a general distribu-
tion over all the warmer countries of the globe — the cuckoos,
the kingfishers, the swifts, and the goatsuckers; while two
others — the trogons and the woodpeckers — are only wanting
in the Australian region, ceasing suddenly at Borneo and
Celebes respectively.

Cuckoos

Whether we consider their wide range, their abundance in
genera and species, or the peculiarities of their organisation,
the cuckoos may be taken as the most typical examples of this
extensive order of birds ; and there is perhaps no part of the
tropics where they do not form a prominent feature in the
ornithology of the country. Their chief food consists of soft
insects, such as caterpillars, grasshoppers, and the defenceless
stick- and leaf-insects ; and in search after these they frequent
the bushes and lower parts of the forest, and the more open
tree-clad plains. They vary greatly in size and appearance,
from the small and beautifully metallic golden- cuckoos of

in ANIMAL LIFE IN THE TROPICAL FORESTS 297

Africa, Asia, and Australia, no larger than sparrows, to the
pheasant-like ground cuckoo of Borneo, the Scythrops of the
Moluccas, which almost resembles a hornbill, the Rhamp-
hococcyx of Celebes with its richly -coloured bill, and the
Goliath cuckoo of Gilolo with its enormously long and ample
tail.

Cuckoos, being invariably weak and defenceless birds,
conceal themselves as much as possible among foliage or
herbage ; and as a further protection, many of them have
acquired the coloration of rapacious or combative birds. In
several parts of the world cuckoos are coloured exactly like
hawks, while some of the small Malayan cuckoos closely
resemble the pugnacious drongo-shrikes.

Trogons, Barlets, Toucans, and HornbUls
Many of the families of Picariae are confined to the tropical
forests, and are remarkable for their varied and beautiful
colouring. Such are the trogons of America, Africa, and
Malaya, whose dense puffy plumage exhibits the purest tints
of rosy-pink, yellow, and white, set off by black heads and a
golden-green or rich brown upper surface. Of more slender
forms, but hardly less brilliant in colour, are the jacamars and
motmots of America, with the bee-eaters and rollers of the
East, the latter exhibiting tints of pale-blue or verditer-green,
which are very unusual. The barbets are rather clumsy fruit-
eating birds, found in all the great tropical regions except that
of the Austro- Malay islands, and they exhibit a wonderful
variety as well as strange combinations of colours. Those of
Asia and Malaya are mostly green, but adorned about the
head and neck with patches of the most vivid reds, blues, and
yellows in endless combinations. The African species are
usually black or greenish-black, with masses of intense crim-
son, yellow, or white, mixed in various proportions and
patterns ; while the American species combine both styles of
colouring, but the tints are usually more delicate, and are
often more varied and more harmoniously interblended. In
the Messrs. Marshall's fine work x all the species are described
and figured, and few more instructive examples can be found

1 A Monograph of the Capitonidm or Scansorial Barbels, by C. F. T.
Marshall and G. F. L. Marshall. 1871.

298 TROPICAL NATURE

than are exhibited in their beautifully-coloured plates, of the
endless ways in which the most glaring and inharmonious
colours are often combined in natural objects with a generally
pleasing result.

We will next group together three families which, although
quite distinct, may be said to represent each other in their
respective countries, — the toucans of America, the plantain-
eaters of Africa, and the hornbills of the East, — all being
large and remarkable birds, and certain to attract the tra-
veller's attention. The toucans are the most beautiful on
account of their large and richly-coloured bills, their delicate
breast-plumage, and the varied bands of colour with which
they are often adorned. Though feeding chiefly on fruits,
they also devour birds' eggs and young birds ; and they are
remarkable for the strange habit of sleeping with the tail laid
flat upon their backs, in what seems a most unnatural and
inconvenient position. What can be the use of their enor-
mous bills has been a great puzzle to naturalists, the only
tolerably satisfactory solution yet arrived at being that sug-
gested by Mr. Bates, — that it simply enables them to reach
fruit at the ends of slender twigs which, owing to their weight
and clumsiness, they would otherwise be unable to obtain.
At first sight it appears very improbable that so large and
remarkable an organ should have been developed for such a
purpose; but we have only to suppose that the original
toucans had rather large and thick bills, not unlike those of
the barbets (to which group they are undoubtedly allied), and
that as they increased in size and required more food, only
those could obtain a sufficiency whose unusually large beaks
enabled them to reach farthest. So large and broad a bill as
they now possess would not be required; but the develop-
ment of the bill naturally went on as it had begun, and, so
that it was light and handy, the large size was no disadvantage
if length was obtained. The plantain-eaters of Africa are less
remarkable birds, though adorned with rich colours and
elegant crests. The hornbills, though less beautiful than the
toucans, are more curious, from the strange forms of their
huge bills, which are often adorned with ridges, knobs, or
recurved horns. They are bulky and heavy birds, and during
flight beat the air with prodigious force, producing a rushing

in ANIMAL LIFE IN THE TROPICAL FORESTS 299

sound very like the puff of a locomotive, and which can some-
times be heard a mile off. They mostly feed on fruits; and
as their very short legs render them even less active than the
toucans, the same explanation may be given of the large size
of their bills, although it will not account for the curious
horns and processes from which they derive their distinctive
name. The largest hornbills are more than four feet long,
and their laboured noisy flight and huge bills, as well as their
habit of perching on the top of bare or isolated trees, render
them very conspicuous objects.

The Picariae comprise many other interesting families —
as, for example, the puff-birds, the todies, and the humming-
birds ; but as these are all confined to America we can hardly
claim them as characteristic of the tropics generally. Others,
though very abundant in the tropics, like the kingfishers and
the goatsuckers, are too well known in temperate lands to
allow of their being considered as specially characteristic of
the equatorial zone. We will therefore pass on to consider
what are the more general characteristics of the tropical as
compared with the temperate bird-fauna, especially as exem-
plified among the true perchers or Passeres, which constitute
about three-fourths of all terrestrial birds.

Passeres

This great order comprises all our most familiar birds,
such as the thrushes, warblers, tits, shrikes, flycatchers,
starlings, crows, wagtails, larks, and finches. These families
are all more or less abundant in the tropics ; but there are
a number of other families which are almost or quite peculiar
to tropical lands and give a special character to their bird-
life. All the peculiarly tropical families are, however, con-
fined to some definite portion of the tropics, a number of
them being American only, others Australian, while others
again are common to all the warm countries of the Old
World ; and it is a curious fact that there is no single family of
this great order of birds that is common to all tropical regions
and confined to them, or that is even especially characteristic
of the tropical zone, like the cuckoos among the Picarise.
The tropical families of passerine birds being very numerous,
and their peculiarities not easily understood by any but orni-

TROPICAL NATUEE

thologists, it will be better to consider the series of fifty
families of Passeres as one compact group, and endeavour to
point out what external peculiarities are most distinctive of
those which inhabit tropical countries.

Owing to the prevalence of forests and the abundance of
flowers, fruits, and insects, tropical and especially equatorial
birds have become largely adapted to these kinds of food ;
while the seed-eaters, which abound in temperate lands where
grasses cover much of the surface, are proportionately scarce.
Many of the peculiarly tropical families are therefore either
true insect-eaters or true fruit-eaters, whereas in the tem-
perate zones a mixed diet is more general.

One of the features of tropical birds that will first strike
the observer is the prevalence of crests and of ornamental
plumage in various parts of the body, and especially of ex-
tremely long or curiously shaped feathers in the tails, tail-
coverts, or wings of a variety of species. As examples we
may refer to the red paradise-bird, whose middle tail-feathers
are like long ribands of whalebone ; to the wire-like tail
feathers of the king bird-of-paradise of New Guinea, and of
the wire-tailed manakin of the Amazons ; and to the long
waving tail plumes of the whydah finch of West Africa and
paradise flycatcher of India ; to the varied and elegant crests
of the cock-of-the-rock, the king-tyrant, the umbrella-bird,
and the six-plumed bird-of-paradise ; and to the wonderful
side plumes of most of the true paradise-birds. In other
orders of birds we have such remarkable examples as the
racquet-tailed kingfishers of the Moluccas, and the racquet-
tailed parrots of Celebes ; the enormously developed tail-
coverts of the peacock and the Mexican trogon; and the
excessive wing-plumes, of the argus-pheasant of Malacca and
the long-shafted goatsucker of West Africa.

Still more remarkable are the varied styles of coloration
in the birds of tropical forests, which rarely or never appear
in those of temperate lands. We have intensely lustrous
metallic plumage in the jacamars, trogons, humming-birds,
sun-birds, and paradise-birds ; as well as in some starlings,
pittas or ground thrushes, and drongo-shrikes. Pure green
tints occur in parrots, pigeons, green bulbuls, greenlets, and
in some tanagers, finches, chatterers, and pittas. These

in ANIMAL LIFE IN THE TROPICAL FORESTS 301

undoubtedly tend to concealment; but we have also the
strange phenomenon of white forest birds in the tropics, a
colour only found elsewhere among the aquatic tribes and in
the arctic regions. Thus, we have the bell-bird of South
America, the white pigeons and cockatoos of the East, with
a few starlings, woodpeckers, kingfishers, and goatsuckers,
which are either very light - coloured or in great part pure
white.

But besides these strange and new and beautiful forms
of bird life, which we have attempted to indicate as charac-
terising the tropical regions, the traveller will soon find that
there are hosts of dull and dingy birds, not one whit different,
so far as colour is concerned, from the sparrows, warblers,
and thrushes of our northern climes. He will, however, if
observant, soon note that most of these dull colours are pro-
tective; the groups to which they belong frequenting low
thickets, or the ground, or the trunks of trees. He will find
groups of birds specially adapted to certain modes of tropical
life. Some live on ants upon the ground, others pick minute
insects from the bark of trees ; one group will devour bees
and wasps, others prefer caterpillars ; while a host of small
birds seek for insects in the corollas of flowers. The air, the
earth, the undergrowth, the tree-trunks, the flowers, and the
fruits, all support their specially adapted tribes of birds.
Each species fills a place in nature, and can only continue to
exist so long as that place is open to it ; and each has become
what it is in every detail of form, size, structure, and even of
colour, because it has inherited through countless ancestral
forms all those variations which have best adapted it among
its fellows to fill that place, and to leave behind it equally
well adapted successors.

REPTILES AND AMPHIBIA

Next to the birds, or perhaps to the less observant eye
even before them, the abundance and variety of reptiles form
the chief characteristic of tropical nature ; and the three
groups— lizards, snakes, and frogs— comprise all that, from
our present point of view, need be noticed.

TROPICAL NATURE

Lizards

Lizards are by far the most abundant in individuals and
the most conspicuous ; and they constitute one of the first
attractions to the visitor from colder lands. They literally
swarm everywhere. In cities they may be seen running
along walls and up palings ; sunning themselves on logs of
wood, or creeping up to the eaves of cottages. In every
garden, road, or dry sandy path, they scamper aside as you
walk along. They crawl up trees, keeping at the farther side
of the trunk and watching the passer-by with the caution of
a squirrel. Some will walk up smooth walls with the greatest
ease ; while in houses the various kinds of Geckos cling to
the ceilings, along which they run back downwards in pursuit
of flies, holding on by means of their dilated toes with
suctorial discs, though sometimes, losing hold, they fall upon
the table or on the upturned face of the visitor. In the
forests large, flat, and marbled Geckos cling to the smooth
trunks ; small and active lizards rest on the foliage ; while
occasionally the larger kinds, three or four feet long, rustle
heavily as they move among the fallen leaves.

Their colours vary much, but are usually in harmony with
their surroundings and habits. Those that climb about walls
and rocks are stone -coloured, and sometimes nearly black;
the house lizards are gray or pale -ashy, and are hardly
visible on a palm - leaf thatch, or even on a white - washed
ceiling. In the forest they are often mottled with ashy-green,
like lichen -grown bark. Most of the ground - lizards are
yellowish or brown ; but some are of beautiful green colours,
with very long and slender tails. These are among the most
active and lively ; and instead of crawling on their bellies
like many lizards, they stand well upon their feet and
scamper about with the agility and vivacity of kittens.
Their tails are very brittle ; a slight blow causing them to
snap off, when a new one grows, which is, however, not
so perfectly formed and completely scaled as the original
member. It is not uncommon, when a tail is half broken,
for a new one to grow out of the wound, producing the
curious phenomenon of a forked tail. There are about 1300
different kinds of lizards known, the great majority of which

in ANIMAL LIFE IN THE TROPICAL FORESTS 303

inhabit the tropics, and they probably increase in numbers
towards the equator. A rich vegetation and a due propor-
tion of moisture and sunshine seem favourable to them, as
shown by their great abundance and their varied kinds at
Para and in the Am islands — places which are nearly the
antipodes of each other, but which both enjoy the fine equa-
torial climate in perfection, and are alike pre-eminent in the
variety and beauty of their insect life.

Three peculiar forms of lizard may be mentioned as
specially characteristic of the American, African, and Asiatic
tropical zones respectively. The iguanas of South America
are large, arboreal, herbivorous lizards of a beautiful green
colour, which renders them almost invisible when resting
quietly among foliage. They are distinguished by the
serrated back, deep dew-lap, and enormously long tail, and
are one of the few kinds of lizards whose flesh is considered
a delicacy. The chameleons of Africa are also arboreal
lizards, and they have the prehensile tail, which is more
usually found among American animals. They are excessively
slow in their motions, and are protected by the wonderful
power of changing their colour so as to assimilate it with
that of immediately surrounding objects. Like the majority
of lizards they are insectivorous, but they are said to be
able to live for months without taking food. The dragons
or flying lizards of India and the larger Malay islands are
perhaps the most curious and interesting of living reptiles,
owing to their power of passing through the air by means of
wing-like membranes, which stretch along each side of the
body and are expanded by means of slender bony processes
from the first six false ribs. These membranes are folded
up close to the body when not in use, and are then almost
imperceptible ; but when open they form a nearly circular
web, the upper surface of which is generally zoned with red
or yellow in a highly ornamental manner. By means of this
parachute the animal can easily pass from one tree to another
for a distance of about thirty feet, descending at first, but as it
approaches its destination rising a little so to reach the tree
with its head erect. They are very small, being usually
not more than two or three inches long, exclusive of the
slender tail ; and when the wings are expanded in the sun-

304 TROPICAL NATURE

shine they more resemble some strange insects than members
of the reptile tribe.

Snakes

Snakes are, fortunately, not so abundant or so obtrusive as
lizards, or the tropics would be scarcely habitable. At first,
indeed, the traveller is disposed to wonder that he does not see
more of them, but he will soon find out that there are plenty ;
and, if he is possessed by the usual horror or dislike of them,
he may think there are too many. In the equatorial zone
snakes are less troublesome than in the drier parts of the
tropics, although they are probably more numerous and
more varied. This is because the country is naturally a
vast forest, and the snakes being all adapted to a forest
life do not as a rule frequent gardens and come into houses
as in India and Australia, where they are accustomed to open
and arid places. One cannot traverse the forest, however,
without soon coming upon them. The slender green whip-
snakes glide among the foliage, and may often be touched
before they are seen. The ease and rapidity with which
these snakes pass through bushes, almost without disturbing
a leaf, is very curious. More dangerous are the green vipers,
which lie coiled motionless upon foliage, where their colour
renders it difficult to see them. The writer has often come
upon them while creeping through the jungle after birds or
insects, and has sometimes only had time to draw back when
they were within a few inches of his face. It is startling in
walking along a forest path to see a long snake glide away
from just where you were going to set down your foot ; but
it is perhaps even more alarming to hear a long-drawn heavy
slur-r-r, and just to catch a glimpse of a serpent as thick as
your leg and an unknown number of feet in length, showing
that you must have passed unheeding within a short dis-
tance of where it was lying. The smaller pythons are not,
however, dangerous, and they often enter houses to catch and
feed upon the rats, and are rather liked by the natives. You
will sometimes be told when sleeping in a native house that
there is a large snake in the roof, and that you need not be
disturbed in case you should hear it hunting after its prey.
These serpents no doubt sometimes grow to an enormous

in ANIMAL LIFE IN THE TROPICAL FORESTS 305

size, but such monsters are rare. In Borneo, Mr. St. John
states that he measured one twenty-six feet long, probably
the largest ever measured by a European in the East. The
great water -boa of South America is believed to reach the
largest size. Mr. Bates measured skins twenty-one feet long,
but the largest ever met with by a European appears to be
that described by the botanist, Dr. Gardiner, in his Travels in
Brazil. It had devoured a horse, and was found dead, en-
tangled in the branches of a tree overhanging a river, into
which it had been carried by a flood. It was nearly forty
feet long. These creatures are said to seize and devour full-
sized cattle on the Eio Branco ; and from what is known of
their habits this is by no means improbable.

Frogs and Toads

The only Amphibia that often meet the traveller's eye in
equatorial countries are the various kinds of frogs and toads,
and especially the elegant tree-frogs. When the rainy season
begins, and dried-up pools and ditches become filled with
water, there is a strange nightly concert produced by the
frogs, some of which croak, others bellow, while many have
clanging or chirruping, and not unmusical notes. In roads
and gardens one occasionally meets huge toads six or seven
inches long ; but the most abundant and most interesting of
the tribe are those adapted for an arboreal life, and hence
called tree-frogs. Their toes terminate in discs, by means of
which they can cling firmly to leaves and stems. The majority
of them are green or brown, and these usually feed at night,
sitting quietly during the day so as to be almost invisible,
owing to their colour and their moist shining skins so closely
resembling vegetable surfaces. Many are beautifully marbled
and spotted, and when sitting on leaves resemble large beetles
more than frogs, while others are adorned with bright and
staring colours ; and these, as Mr. Belt has discovered, have
nauseous secretions which render them uneatable, so that they
have no need to conceal themselves. Some of these are bright
blue, others are adorned with yellow stripes, or have a red
body with blue legs. Of the smaller tree-frogs of the tropics
there must be hundreds of species still unknown to naturalists.

TROPICAL NATURE

MAMMALIA

Monkeys

The highest class of animals, the Mammalia, although
sufficiently abundant in all equatorial lands, are those
which are least seen by the traveller. There is, in fact,
only one group — the monkeys — which are at the same time
pre-eminently tropical, and which make themselves perceived
as one of the aspects of tropical nature. They are to be met
with in all the great continents and larger islands, except
Australia, New Guinea, and Madagascar, though the latter island
possesses the lower allied form of Lemurs ; and they never
fail to impress the observer with a sense of the exuberant
vitality of the tropics. They are pre-eminently arboreal in
their mode of life, and are consequently most abundant and
varied where vegetation reaches its maximum development.
In the East we find that maximum in Borneo, and in the
West African forests ; while in the West the great forest
plain of the Amazon stands pre-eminent. It is near the
equator only that the great Anthropoid apes, the gorilla,
chimpanzee, and orang-utan are found, and they may be met
with by any persevering explorer of the jungle. The gibbons,
or long-armed apes, have a wider range in the Asiatic con-
tinent and in Malaya, and they are more abundant both in
species and individuals. Their plaintive howling notes may
often be heard in the forests, and they are constantly to be
seen sporting at the summits of the loftiest trees, swinging
suspended by their long arms, or bounding from tree to tree
with incredible agility. They pass through the forest at a
height of a hundred feet or more, as rapidly as a deer will
travel along the ground beneath them. Other monkeys of
various kinds are more abundant and usually less shy ; and in
places where firearms are not much used they will approach
the houses and gambol in the trees undisturbed by the
approach of man. The most remarkable of the tailed monkeys
of the East is the proboscis monkey of Borneo, whose long
fleshy nose gives it an aspect very different from that of most
of its allies.

In tropical America monkeys are even more abundant
than in the East, and they present many interesting pecu-

in ANIMAL LIFE IN THE TROPICAL FORESTS 307

liarities. They differ somewhat in dentition and in other
structural features from all Old World apes, and a consider-
able number of them have prehensile tails, a peculiarity never
found elsewhere. In the howlers and the spider monkeys
the tail is very long and powerful, and by twisting the
extremity round a branch the animal can hang suspended as
easily as other monkeys can by their hands. It is, in fact, a
fifth hand, and is constantly used to pick up small objects
from the ground. The most remarkable of the American
monkeys are the howlers, whose tremendous roaring exceeds
that of the lion or the bull, and is to be heard frequently at
morning and evening in the primeval forests. The sound is
produced by means of a large, thin, bony vessel in the throat,
into which air is forced ; and it is very remarkable that this
one group of monkeys should possess an organ not found in
any other monkey or even in any other mammal, apparently
for no other purpose than to be able to make a louder noise
than the rest. The only other monkeys worthy of special
attention are the marmosets, beautiful little creatures with
crests, whiskers, or manes, in outward form resembling squirrels,
but with a very small monkey -like face. They are either
black, brown, reddish, or nearly white in colour, and are the
smallest of the monkey tribe, some of them being only about
six inches long exclusive of the tail.

Bats

Almost the only other order of mammals that is specially
and largely developed in the tropical zone is that of the
Chiroptera or bats, which becomes suddenly much less plenti-
ful when we pass into the temperate regions, and still more
rare towards the colder parts of it, although a few species
appear to reach the Arctic circle. The characteristics of the
tropical bats are their great numbers and variety, their large
size, and their peculiar forms or habits. In the East those
which most attract the traveller's attention are the great fruit-
bats, or fly ing -foxes as they are sometimes called, from the
rusty colour of the coarse fur and the fox-like shape of the
head. These creatures may sometimes be seen in immense
flocks which take hours to pass by, and they often devastate
the fruit plantations of the natives. They are often five feet

TROPICAL NATURE

across the expanded wings, with the body of a proportionate
size ; and when resting in the daytime on dead trees, hanging
head downwards, the branches look as if covered with some
monster fruits. The descendants of the Portuguese in the East
use them for food, but all the native inhabitants reject them.

In South America there is a group of bats which are sure
to attract attention. These are the so-called vampires or
blood-suckers, which abound in most parts of tropical Amer-
ica, and are especially plentiful in the Amazon valley. Their
carnivorous propensities were once discredited, but are too
well authenticated. Horses and cattle are often bitten, and
are found in the morning covered with blood, and repeated
attacks weaken and ultimately destroy them. Some persons
are especially subject to the attacks of these bats; and as
native huts are never sufficiently close to keep them out,
these unfortunate individuals are obliged to sleep completely
muffled up in order to avoid being made seriously ill or even
losing their lives. The exact manner in which the attack is
made is not positively known, as the sufferer never feels the
wound. The present writer was once bitten on the toe,
which was found bleeding in the morning from a small round
hole from which the flow of blood was not easily stopped.
On another occasion, when his feet were carefully covered
up, he was bitten on the tip of the nose, only awaking to find
his face streaming with blood. The motion of the wings fans
the sleeper into a deeper slumber, and renders him insensible
to the gentle abrasion of the skin either by teeth or tongue.
This ultimately forms a minute hole, the blood flowing from
which is sucked or lapped up by the hovering vampire. The
largest South American bats, having wings from two to two and
a half feet in expanse, are fruit-eaters like the Pteropi of the
East, the true blood-suckers being small or of medium size,
and varying in colour in different localities. They belong to
the genus Desmodus, and have a tongue with horny papillae
at the end ; and it is probably by means of this that they
abrade the skin and produce a small round wound. This is
the account given by Buffon and Azara, and there seems now
little doubt that it is correct.

Beyond these two great types — the monkeys and the bats
— we look in vain among the varied forms of mammalian life

in ANIMAL LIFE IN THE TROPICAL FORESTS 309

for any that can be said to be distinctive of the tropics as
compared with the temperate regions. Many peculiar groups
are tropical, but they are in almost every case confined to
limited portions of the tropical zones, or are rare in species or
individuals. Such are the lemurs in Africa, Madagascar, and
Southern Asia ; the tapirs of America and Malaya ; the rhino-
ceroses and elephants of Africa and Asia ; the cavies and the
sloths of America ; the scaly ant>eaters of Africa and Asia ;
but none of these are sufficiently numerous to come often
before the traveller so as to affect his general ideas of the
aspects of tropical life, and they are, therefore, out of place
in such a sketch of those aspects as we are here attempting
to lay before our readers.

Summary of tlie Aspects of Animal Life in the Tropics
We will now briefly summarise the general aspects of
animal life as forming an ingredient in the scenery and natural
phenomena of the equatorial regions. Most prominent are
the butterflies, owing to their numbers, their size, and their
brilliant colours, as well as their peculiarities of form, and
the slow and majestic flight of many of them. In other
insects, the large size and frequency of protective colours
and markings are prominent features, together with the
inexhaustible profusion of the ants and other small insects.
Among birds the parrots stand forth as the pre-eminent
tropical group, as do the apes and monkeys among mammals,
the two groups having striking analogies in the prehensile
hand and the power of imitation. Of reptiles, the two most
prominent groups are the lizards and the frogs ; the snakes,
though equally abundant, being much less obtrusive.

Animal life is, on the whole, far more abundant and more
varied within the tropics than in any other part of the globe,
and a great number of peculiar groups are found there which
never extend into temperate regions. Endless eccentricities
of form and extreme richness of colour are its most prominent
features, and these are manifested in the highest degree in
those equatorial lands where the vegetation acquires its
greatest beauty and its fullest development. The causes of
these essentially tropical features are not to be found in the
comparatively simple influence of solar light and heat, but

310 TROPICAL NATURE

rather in the uniformity and permanence with which these
and all other terrestrial conditions have acted, neither varying
prejudicially throughout the year, nor having undergone any
important change for countless past ages. While successive
glacial periods have devastated the temperate zones, and
destroyed most of the larger and more specialised forms which
during more favourable epochs had been developed, the equa-
torial lands must always have remained thronged with life,
and have been unintermittingly subject to those complex
influences of organism upon organism which seem the main
agents in developing the greatest variety of forms and filling
up every vacant place in nature. A constant struggle against
the vicissitudes and recurring severities of climate must always
have restricted the range of effective animal variation in the
temperate and frigid zones, and have checked all such develop-
ments of form and colour as were in the least degree injurious
in themselves, or which co- existed with any constitutional
incapacity to resist great changes of temperature or other
unfavourable conditions. Such disadvantages were not ex-
perienced in the equatorial zone. The struggle for existence
as against the forces of nature was there always less severe ;
food was there more abundant and more regularly supplied ;
shelter and concealment were at all times more easily ob-
tained; and almost the only physical changes experienced,
being dependent on cosmical or geological revolutions, were so
slow that variation and natural selection were always able to
keep the teeming mass of organisms in nicely balanced har-
mony with the changing physical conditions. The equatorial
zone, in short, exhibits to us the result of a comparatively
continuous and unchecked development of organic forms ;
while in the temperate regions there have been a series of
periodical checks and extinctions of a more or less disastrous
nature, necessitating the commencement of the work of de-
velopment in certain lines over and over again. In the one,
evolution has had a fair chance; in the other, it has had
countless difficulties thrown in its way. The equatorial regions
are then, as regards their past and present life-history, a more
ancient world than that represented by the temperate zones,
a world in which the laws which have governed the progress-
ive development of life have operated with comparatively

in ANIMAL LIFE IN THE TROPICAL FORESTS 311

little check for countless ages, and have resulted in those
infinitely varied and beautiful forms— those wonderful eccen-
tricities of structure, of function, and of instinct — that rich
variety of colour, and that nicely balanced harmony of rela-
tions, which delight and astonish us in the animal productions
of all tropical countries.

IV
HUMMING-BIRDS

AS ILLUSTEATING THE LUXURIANCE OF TROPICAL NATURE

Structure — Colours and Ornaments — Descriptive Names — The Motions
and Habits of Humming-birds — Display of Ornaments by the Male —
Food — Nests — Geographical Distribution and Variation — Humming-
birds of Juan Fernandez as illustrating Variation and Natural Selec-
tion— The Relations and Affinities of Humming-birds — How to Deter-
mine doubtful Affinities — Resemblances of Swifts and Humming-birds
— Differences between Sun-birds and Humming-birds — Conclusion.

THERE are now about ten thousand different kinds of birds
known to naturalists, and these are classed in one hundred
and thirty families, which vary greatly in extent, some con-
taining a single species only, while others comprise many
hundreds. The two largest families are those of the warblers,
with more than six hundred, and the finches with more than
five hundred species, spread over the whole globe ; the hawks
and the pigeons, also spread over the whole globe, number
about three hundred and thirty and three hundred and sixty
species respectively ; while the diminutive humming-birds,
confined to one hemisphere, consist of about four hundred
different species. They are thus, as regards the number of
distinct kinds collected in a limited area, the most remarkable
of all the families of birds. It may, however, very reasonably
be asked, whether the four hundred species of humming-birds
above alluded to are really all distinct — as distinct on the
average as the ten thousand species of birds are from each
other. We reply that they certainly are perfectly distinct
species, which never intermingle ; and their differences do not
consist in colour only, but in peculiarities of form, of structure,

HUMMING-BIRDS 313

and of habits ; so that they have to be classed in more than a
hundred distinct genera or systematic groups of species, these
genera being really as unlike each other as stonechats and
nightingales, or as partridges and blackcocks. The figures we
have quoted, as showing the proportion of birds in general to
humming-birds, thus represent real facts ; and they teach us
that these small and in some respects insignificant birds con-
stitute an important item in the animal life of the globe.

Humming-birds are, in many respects, unusually interesting
and instructive. They are highly peculiar in form, in struc-
ture, and in habits, and are quite unrivalled as regards variety
and beauty. Though the name is familiar to every one, few
but naturalists are acquainted with the many curious facts in
their history, or know how much material they afford for
admiration and study. It is proposed, therefore, to give a
brief and popular account of the form, structure, habits, dis-
tribution, and affinities of this remarkable family of birds, as
illustrative of the teeming luxuriance of tropical nature, and
as throwing light on some of the most interesting problems of
natural history.

Structure

The humming-birds form one compact family named
Trochilidse. They are all small birds, the largest known being
about the size of a swallow, while the smallest are minute
creatures, whose bodies are hardly larger than a humble-bee.
Their distinguishing features are excessively short legs and
feet, very long and pointed wings, a long and slender bill,
and a long extensible tubular tongue; and these characters are
found combined in no other birds. The feet are exceedingly
small and delicate, often beautifully tufted with down, and so
short as to be hardly visible beyond the plumage. The toes
are placed as in most birds, three in front and one behind,
and have very strong and sharply curved claws ; and the feet
serve probably to cling to a perch rather than to give any
movement to the body. The wings are long and narrow, but
strongly formed ; and the first quill is the longest, a peculiarity
found in hardly any other birds but a few of the swifts. The
bill varies greatly in length, but is always long, slender, and
pointed, the upper mandible being the widest and lapping

314 TROPICAL NATURE

over the lower at each side, thus affording complete protection
to the delicate tongue, the perfect action of which is essential
to the bird's existence. The humming-bird's tongue is very
long, and is capable of being greatly extended beyond the
beak and rapidly drawn back, by means of muscles which are
attached to the hyoid or tongue-bones, and bend round over
the back and top of the head to the very forehead, just as in
the woodpeckers. The two blades or laminae of which the
tongues of birds usually seem to be formed are here greatly
lengthened, broadened out, and each rolled up ; so as to form
a complete double tube connected down the middle, and with
the outer edges in contact but not united. The extremities
of the tubes are, however, flat and fibrous. This tubular and
retractile tongue enables the bird to suck up honey from the
nectaries of flowers, and also to capture small insects ; but
whether the latter pass down the tubes, or are entangled in
the fibrous tips and thus draw back into the gullet, is not
known. The only other birds with a similar tubular tongue are
the sun-birds of the East, which, however, as we shall presently
explain, have no affinity whatever with the humming-birds.

Colours and Ornaments

The colours of these small birds are exceedingly varied and
exquisitely beautiful. The basis of the colouring may be said
to be green, as in parrots ; but whereas in the latter it is a
silky green, in humming-birds it is always metallic. The
majority of the species have some green about them, especially
on the back ; but in a considerable number rich blues, purples,
and various shades of red are the prevailing tints. The
greater part of the plumage has more or less of a metallic
gloss, but there is almost always some part which has an
intenser lustre, as if actually formed of scales of burnished
metal. A gorget, covering the greater part of the neck and
breast, most commonly displays this vivid colour ; but it also
frequently occurs on the head, on the back, on the tail-coverts
above or below, on the upper surface of the tail, on the
shoulders or even the quills. The hue of every precious
stone and the lustre of every metal is here represented ;
and such terms as topaz, amethyst, beryl, emerald, garnet,
ruby, sapphire; golden, golden-green, coppery, fiery, glowing,

HUMMING-BIRDS 315

iridescent, refulgent, celestial, glittering, shining, are con-
stantly used to name or describe the different species.

No less remarkable than the colours are the varied develop-
ments of plumage with which these birds are adorned. The
head is often crested in a variety of ways ; either a simple
flat crest, or with radiating feathers, or diverging into two
horns, or spreading laterally like wings, or erect and bushy,
or recurved and pointed like that of a plover. The throat
and breast are usually adorned with broad scale-like feathers,
or these diverge into a tippet, or send out pointed collars, or
elegant frills of long and narrow plumes tipped with metallic
spots of various colours. But the tail is even a more varied
and beautiful ornament, either short and rounded, but pure
white or some other strongly contrasted tint ; or with short
pointed feathers forming a star; or with the three outer
feathers on each side long and tapering to a point ; or larger,
and either square or round, or deeply forked or acutely
pointed; or with the two middle feathers excessively long
and narrow ; or with the tail very long and deeply forked,
with broad and richly-coloured feathers; or with the two
outer feathers wire-like and having broad spoon-shaped tips.
All these ornaments, whether of the head, neck, breast, or
tail, are invariably coloured in some effective or brilliant
manner, and often contrast strikingly with the rest of the
plumage. Again, these colours often vary in tint according
to the direction in which they are seen. In some species they
must be looked at from above, in others from below ; in some
from the front, in others from behind, in order to catch the full
glow of the metallic lustre ; hence, when the birds are seen in
their native haunts, the colours come and go and change with
their motions, so as to produce a startling and beautiful effect.

The bill differs greatly in length and shape, being either
straight or gently curved, in some species bent like a sickle,
in others turned up like the bill of the avoset. It is usually
long and slender, but in one group is so enormously developed
that it is nearly the same length as the rest of the bird. The
legs, usually little seen, are in some groups adorned with
globular tufts of white, brown, or black down, a peculiarity
possessed by no other birds. The reader will now be in a
position to understand how the four hundred species of

316 TROPICAL NATURE

humming-birds may be easily distinguished, by the varied
combinations of the characters here briefly enumerated, to-
gether with many others of less importance. One group of
birds will have a short round tail, with crest and long neck-
frill; another group a deeply-forked broad tail, combined
with glowing crown and gorget; one is both bearded and
crested; others have a luminous back and pendent neck-
plumes ; and in each of these groups the species will vary in
combinations of colour, in size, and in the proportions of the
ornamental plumes, so as to produce an unmistakable dis-
tinctness; while, without any new developments of form or
structure, there is room for the discovery of hundreds more of
distinct kinds of humming-birds.

Descriptive Names

The name we usually give to the birds of this family is derived
from the sound of their rapidly-moving wings, a sound which
is produced by the largest as well as by the smallest member of
the group. The Creoles of Guiana similarly call them Bourdons
or hummers. The French term, Oiseau-mouche, refers to their
small size ; while Colibri is a native name which has come
down from the Carib inhabitants of the West Indies. The
Spaniards and Portuguese call them by more poetical names,
such as flower-peckers, flower-kissers, myrtle-suckers — while
the Mexican and Peruvian names show a still higher apprecia-
tion of their beauties, their meaning being " rays of the sun,"
" tresses of the day-star," and other such appellations. Even
our modern naturalists, while studying the structure and
noting the peculiarities of these living gems, have been
so struck by their inimitable beauties that they have en-
deavoured to invent appropriate English names for the more
beautiful and remarkable genera. Hence we find in common
use such terms as sun-gems, sun-stars, hill-stars, wood-stars,
sun -angels, star -throats, comets, coquettes, flame -bearers,
sylphs, and fairies ; together with many others derived from
the character of the tail or the crests.

Tlie Motions and Habits of Humming-Birds
Let us now consider briefly the peculiarities of flight, the
motions, the food, the nests, and general habits of the humming-

HUMMING-BIRDS 317

birds, quoting the descriptions of those modern naturalists
who have personally observed them. Their appearance,
remarks Professor Alfred Newton, is entirely unlike that of
any other bird : " One is admiring some brilliant and beauti-
ful flower, when between the blossom and one's eye suddenly
appears a small dark object, suspended as it were between four
short black threads meeting each other in a cross. For an
instant it shows in front of the flower ; again another instant,
and emitting a momentary flash of emerald and sapphire light,
it is vanishing, lessening in the distance, as it shoots away, to
a speck that the eye cannot take note of." Audubon observes
that the Ruby humming-birds pass through the air in long
undulations, but the smallness of their size precludes the pos-
sibility of following them with the eye farther than fifty or
sixty yards, without great difficulty. A person standing in a
garden by the side of a common althaea in bloom, will hear
the humming of their wings and see the little birds themselves
within a few feet of him one moment, while the next they
will be out of sight and hearing. Mr. Gould, who visited
North America in order to see living humming-birds while
preparing his great work on the family, remarks that the
action of the wings reminded him of a piece of machinery
acted upon by a powerful spring. When poised before a
flower, the motion is so rapid that a hazy semicircle of indis-
tinctness on each side of the bird is all that is perceptible.
Although many short intermissions of rest are taken, the bird
may be said to live in the air — an element in which it per-
forms every kind of evolution with the utmost ease, frequently
rising perpendicularly, flying backward, pirouetting or dancing
off, as it were, from place to place, or from one part of a tree
to another, sometimes descending, at others ascending. It
often mounts up above the towering trees, and then shoots off
like a little meteor at a right angle. At other times it gently
buzzes away among the little flowers near the ground ; at one
moment it is poised over a diminutive weed, at the next it is
seen at a distance of forty yards, whither it has vanished with
the quickness of thought.

The Rufous Flame - bearer, an exquisite species found
on the west coast of North America, is thus described by
Mr. Nuttall: "When engaged in collecting its accustomed

318 TROPICAL NATURE

sweets, in all the energy of life, it seemed like a breathing
gem, a magic carbuncle of flaming fire, stretching out its
glorious ruff as if to emulate the sun itself in splendour."
The Sappho Comet, whose long forked tail barred with
crimson and black renders it one of the most imposing of
humming-birds, is abundant in many parts of the Andes ;
and Mr. Bonelli tells us that the difficulty of shooting them
is very great from the extraordinary turns and evolutions
they make when on the wing ; at one instant darting head-
long into a flower, at the next describing a circle in the air
with such rapidity that the eye, unable to follow the move-
ment, loses sight of the bird until it again returns to the
flower which at first attracted its attention. Of the little
Vervain humming-bird of Jamaica, Mr. Gosse writes : "I
have sometimes watched with much delight the evolutions of
this little species at the Moringa-tree.1 When only one is
present, he pursues the round of the blossoms soberly enough.
But if two are at the tree, one will fly off, and suspend
himself in the air a few yards distant ; the other presently
starts off to him, and then, without touching each other, they
mount upwards with strong rushing wings, perhaps for five
hundred feet. They then separate, and each starts diagonally
towards the ground like a ball from a rifle, and, wheeling
round, comes up to the blossoms again as if it had not moved
away at all. The figure of the smaller humming-birds on the
wing, their rapidity, their wavering course, and their whole
manner of flight, are entirely those of an insect." Mr. Bates
remarks that on the Amazons, during the cooler hours of the
morning and from four to six in the afternoon, humming-
birds are to be seen whirring about the trees by scores ; their
motions being unlike those of any other birds. They dart to
and fro so swiftly that the eye can scarcely follow them, and
when they stop before a flower it is only for a few moments.
They poise themselves in an unsteady manner, their wings
moving with inconceivable rapidity, probe the flower, and
then shoot off to another part of the tree. They do not
proceed in that methodical manner which bees follow, taking

1 Sometimes called the horse-radish tree. It is the Moringa pterygosperma,
a native of the East Indies, but commonly cultivated in Jamaica. It has
yellow flowers.

HUMMING-BIRDS 319

the flowers seriatim, but skip about from one part of the tree
to another in the most capricious way. Mr. Belt remarks on
the excessive rapidity of the flight of the humming-bird giving
it a sense of security from danger, so that it will approach a
person nearer than any other bird, often hovering within two
or three yards (or even one or two feet) of one's face. He
watched them bathing in a small pool in the forest, hovering
over the water, turning from side to side by quick jerks of
the tail ; now showing a throat of gleaming emerald, now
shoulders of glistening amethyst; then darting beneath the
water, and rising instantly, throw off a shower of spray from
its quivering wings, and again fly up to an overhanging
bough and commence to preen its feathers. All humming-
birds bathe on the wing, and generally take three or four
dips, hovering between times about three or four inches
above the surface. Mr. Belt also remarks on the immense
numbers of humming-birds in the forests, and the great
difficulty of seeing them ; and his conclusion is, that in the
part of Nicaragua where he was living they equalled in
number all the rest of the birds together, if they did not
greatly exceed them.

The extreme pugnacity of humming-birds has been noticed
by all observers. Mr. Gosse describes two meeting and
chasing each other through the labyrinths of twigs and
flowers till, an opportunity occurring, the one would dart
with seeming fury upon the other, and then, with a loud
rustling of their wings, they would twirl together, round and
round, till they nearly came to the earth. Then they parted,
and after a time another tussle took place. Two of the same
species can hardly meet without an encounter, while in many
cases distinct species attack each other with equal fury. Mr.
Salvin describes the splendid Eugenes fulgens attacking two
other species with as much ferocity as its own fellows.
One will knock another off its perch, and the two will
go fighting and screaming away at a pace hardly to be
followed by the eye. Audubon says they attack any other
birds that approach them, and think nothing of assaulting
tyrant -shrikes and even birds of prey that come too near
their home.

TROPICAL NATURE

Display of Ornaments by the Male

It is a well-known fact that when male birds possess any
unusual ornaments, they take such positions or perform such
evolutions as to exhibit them to the best advantage while
endeavouring to attract or charm the females, or in rivalry
with other males. It is therefore probable that the wonder-
fully varied decorations of humming-birds, whether burnished
breast - shields, resplendent tail, crested head, or glittering
back, are thus exhibited ; but almost the only actual observa-
tion of this kind is that of Mr. Belt, who describes how two
males of the Florisuga mellivora displayed their ornaments
before a female bird. One would shoot up like a rocket,
then, suddenly expanding the snow-white tail like an inverted
parachute, slowly descend in front of her, turning round
gradually to show off both back and front. The expanded
white tail covered more space than all the rest of the bird,
and was evidently the grand feature of the performance.
Whilst one was descending the other would shoot up and
come slowly down expanded.1

Food

The food of humming-birds has been a matter of much
controversy. All the early writers, down to Buffon, believed
that they lived solely on the nectar of flowers ; but since that
time every close observer of their habits maintains that they
feed largely, and in some cases wholly, on insects. Azara
observed them on the La Plata in winter, taking insects out
of the webs of spiders at a time and place where there were
no flowers. Bullock, in Mexico, declares that he saw them
catch small butterflies, and that he found many kinds of
insects in their stomachs. Waterton made a similar state-
ment. Hundreds and perhaps thousands of specimens have
since been dissected by collecting naturalists, and in almost
every instance their stomachs have been found full of insects
— sometimes, but not generally, mixed with a proportion of
honey. Many of them in fact may be seen catching gnats
and other small insects just like fly-catchers, sitting on a dead
twig over water, darting off for a time in the air, and then
1 The Naturalist in Nicaragua, p. 112.

HUMMING-BIRDS 321

returning to the twig. Others come out just at dusk, and
remain on the wing, now stationary, now darting about with
the greatest rapidity, imitating in a limited space the evolu-
tions of the goatsuckers, and evidently for the same end
and purpose. Mr. Gosse also remarks : " All the humming-
birds have more or less the habit, when in flight, of pausing
in the air and throwing the body and tail into rapid and odd
contortions. This is most observable in the Polytmus, from
the effect that such motions have on the long feathers of the
tail. That the object of these quick turns is the capture of
insects, I am sure, having watched one thus engaged pretty
close to me. I observed it carefully, and distinctly saw the
minute flies in the air which it pursued and caught, and
heard repeatedly the snapping of the beak. My presence
scarcely disturbed it, if at all."

There is also an extensive group of small brown humming-
birds, forming the sub-family Phaethornithinse, which rarely
or never visit flowers, but frequent the shady recesses of the
forest, where they hunt for minute insects. They dart about
among the foliage, and visit in rapid succession every leaf
upon a branch, balancing themselves vertically in the air,
passing their beaks closely over the under-surface of each leaf,
and thus capturing, no doubt, any small insects that may
lurk there. While doing this, the two long feathers of the
tail have a vibrating motion, serving apparently as a rudder
to assist them in performing the delicate operation. Others
search up and down stems and dead sticks in the same
manner, every now and then picking off something, exactly
as a bush -shrike or a tree-creeper does, with the difference
that the humming-bird is constantly on the wing ; while the
remarkable sickle-bill is said to probe the scale-covered stems
of palms and tree-ferns to obtain its insect food.

It is a well-known fact that although humming-birds are
easily tamed, they cannot be preserved long in captivity, even
in their own country, when fed only on syrup. Audubon
states that when thus fed they only live a month or two and
die apparently starved ; while if kept in a room whose open
windows are covered with a fine net, so as to allow small
insects to enter, they have been kept for a whole year without
any ill effects. Another writer, Mr. Webber, captured and
Y

322 TROPICAL NATURE

tamed a number of the Kuby-throat in the United States. He
found that when fed for three weeks on syrup they drooped,
but after being let free for a day or two they would return to
the open cage for more of the syrup. Some which had been
thus tamed and set free returned the following year, and at
once flew straight to the remembered little cup of sweets.
Mr. Grosse in Jamaica also kept some in captivity, and found
the necessity of giving them insect food; and he remarks
that they were very fond of a small ant that swarmed on the
syrup with which they were fed. It is strange that, with all
this previous experience and information, those who have
attempted to bring live humming-birds to this country have
fed them exclusively on syrup ; and the weakness produced
by this insufficient food has no doubt been the chief cause of
their death on, or very soon after, arrival. A box of ants
would not be difficult to bring as food for them, but even
finely-chopped meat or yolk of egg would probably serve, in
the absence of insects, to supply the necessary proportion of
animal food.

Nests

The nests of the humming-birds are, as might be expected,
beautiful objects, some being no larger inside than the half of
a walnut shell. These small cup-shaped nests are often placed
in the fork of a branch, and the outside is sometimes beauti-
fully decorated with pieces of lichen, the body of the nest
being formed of cottony substances and the inside lined with
the finest and most silky fibres. Others suspend their nests
to creepers hanging over water, or even over the sea ; and
the Pichincha humming-bird once attached its nest to a straw-
rope hanging from the roof of a shed. Others again build
nests of a hammock-form attached to the face of rocks by
spiders' web; while the little forest-haunting species fasten
their nests to the points or to the under-sides of palm-leaves
or other suitable foliage. They lay only one or two white

Geographical Distribution and Variation

Most persons know that humming-birds are found only in
America; but it is not so generally known that they are
almost exclusively tropical birds, and that the few species that

HUMMING-BIRDS

are found in the temperate (northern and southern) parts of
the continent are migrants, which retire in the winter to the
warmer lands near or within the tropics. In the extreme
north of America two species are regular summer visitants, one
on the east and the other on the west of the Rocky Mountains.
On the east the common North American or Euby-throated
humming-bird extends through the United States and Canada,
and as far as 57° north latitude, or considerably north of
Lake Winnipeg ; while the milder climate of the west coast
allows the Rufous Flame-bearer to extend its range beyond
Sitka to the parallel of 61°. Here they spend the whole
summer, and breed, being found on the Columbia River in the
latter end of April, retiring to Mexico in the winter. Sup-
posing that those which go farthest north do not return
farther south than the borders of the tropics, these little
birds must make a journey of full three thousand miles each
spring and autumn. The antarctic humming-bird visits the
inhospitable shores of Tierra-del-Fuego, where it has been
seen visiting the flowers of fuchsias in a snowstorm, while
it spends the winter in the warmer parts of Chili and
Bolivia.

In the south of California and in the Central United
States three or four other species are found in summer ; but
it is only when we enter the tropics that the number of
different kinds becomes considerable. In Mexico there are
more than thirty species, while in the southern parts of
Central America there are more than double that number.
As we go on towards the equator they become still more
numerous, till they reach their maximum in the equatorial
Andes. They especially abound in the mountainous regions ;
while the luxuriant forest plains of the Amazons, in which so
many other forms of life reach their maximum, are very poor
in humming-birds. Brazil, being more hilly and with more
variety of vegetation, is richer, but does not equal the Andean
valleys, plateaux, and volcanic peaks. Each separate district
of the Andes has its peculiar species and often its peculiar
genera, and many of the great volcanic mountains possess
kinds which are confined to them. Thus, on the great
mountain of Pichincha there is a peculiar species found at an
elevation of about fourteen thousand feet only ; while an

TROPICAL NATURE

allied species on Chimborazo ranges from fourteen thousand
feet to the limits of perpetual snow at sixteen thousand feet
elevation. It frequents a beautiful yellow- flowered alpine
shrub belonging to the Asteracese. On the extinct volcano of
Chiriqui in Veragua a minute humming-bird, called the little
Flame -bearer, has been only found inside the crater. Its
scaled gorget is of such a flaming crimson that, as Mr. Gould
remarks, it seems to have caught the last spark from the
volcano before it was extinguished.

Not only are humming-birds found over the whole extent
of America, from Sitka to Tierra-del-Fuego, and from the
level of the sea to the snow-line on the Andes, but they in-
habit many of the islands at a great distance from the main-
land. The West Indian islands possess fifteen distinct species
belonging to eight different genera, and these are so unlike
any found on the continent that five of these genera are
peculiar to the Antilles. Even the Bahamas, so close to
Florida, possess two peculiar species. The small group of
islands called Tres Marias, about sixty miles from the west
coast of Mexico, has a peculiar species. More remarkable are
the two humming-birds of Juan Fernandez, situated in the
Pacific Ocean, four hundred miles west of Valparaiso in Chili,
one of these being peculiar; while another species inhabits
the little island Mas-afuera, ninety miles farther west. The
Galapagos, though very little farther from the mainland and
much more extensive, have no humming-birds ; neither have
the Falkland islands, and the reason seems to be that both
these groups are deficient in forest, and in fact have hardly
any trees or large shrubs, while there is a great paucity of
flowers and of insect life.

Humming-birds of Juan Fernandez as illustrating Variation and

Natural Selection

The three species Avhich inhabit Juan Fernandez and Mas-
afuera present certain peculiarities of great interest. They
form a distinct genus, Eustephanus, one species of which in-
habits Chili as well as the island of Juan Fernandez. This,
which may be termed the Chilian species, is greenish in both
sexes, whereas in the two species peculiar to the islands the
males are red or reddish-brown, and the females green. The

HUMMING-BIRDS

two red males differ very slightly from each other, but the
three green females differ considerably j and the curious point
is that the female in the smaller and more distant island some-
what resembles the same sex in Chili, while the female of the
Juan Fernandez species is very distinct, although the males
of the two islands are so much alike. As this forms a com-
paratively simple case of the action of the laws of variation
and natural selection, it will be instructive to see if we can
picture to ourselves the process by which the changes have
been brought about. We must first go back to an unknown
but rather remote period, just before any humming-birds had
reached these islands. At that time a species of this peculiar
genus, Eustephanus, must have inhabited Chili ; but we can-
not be sure that it was identically the same as that which is
now found there, because we know that species are always
undergoing change to a greater or less degree. After perhaps
many failures, one or more pairs of the Chilian bird got blown
across to Juan Fernandez, and finding the country favourable,
with plenty of forests and a fair abundance of flowers and
insects, they rapidly increased and permanently established
themselves on the island. They soon began to change colour,
however, "the male getting a tinge of reddish-brown, which
gradually deepened into the fine colour now exhibited by the
two insular species, while the female, more slowly, changed
to white on the under - surface and on the tail, while the
breast -spots became more brilliant. When the change of
colour was completed in the male, but only partially so in the
female, a further emigration westward took place to the
small island Mas-afuera, where they also established them-
selves. Here, however, the change begun in the larger island
appears to have been checked, for the female remains to this
day intermediate between the Juan Fernandez and the Chilian
forms. More recently, the parent form has again migrated
from Chili to Juan Fernandez, where it still lives side by side
with its greatly changed descendant.1 Let us now see how
far these facts are in accordance with the general laws of

1 In the preceding account of the probable course of events in peopling
these islands with humming-birds, I follow Mr. Sclater's paper on the
"Land Birds of Juan Fernandez," Ibis, 1871, p. 183. In what follows I
give my own explanation of the probable causes of the change.

TROPICAL NATURE

variation, and with those other laws which I have endeavoured
to show regulate the development of colour.1

The amount of variation which is likely to occur in a
species will be greatly influenced by two factors — the occur-
rence of a change in the physical conditions, and the average
abundance or scarcity of the individuals composing the species.
When from these or other causes variation occurs, it may
become fixed as a variety or a race, or may go on increasing
to a certain extent, either from a tendency to vary along
certain special lines induced by local or physiological causes,
or by the continued survival and propagation of all such
varieties as are beneficial to the race. After a certain time
a balance will be arrived at, either by the limits of useful
variation in this one direction having been reached, or by the
species becoming harmoniously adapted to all the surrounding
conditions : and without some change in these conditions the
specific form may then remain unaltered for a very long time ;
whence arises the common impression of the fixity of species.
Now in a country like Chili, forming part of a great continent
very well stocked with all forms of organic life, the majority
of the species would be in a state of stable equilibrium ; the
most favourable variations would have been long ago selected ;
and the numbers of individuals in each species would be
tolerably conBtant, being limited by the numerous other forms
whose food and habits were similar, or which in any way
impinged upon its sphere of existence. We may, therefore,
assume that the Chilian humming-bird which migrated to
Juan Fernandez was a stable form, hardly if at all different
from the existing species which is termed Eustephanus
galeritus. On the island it met with very changed but
highly favourable conditions — an abundant shrubby vegeta-
tion and a tolerably rich flora ; less extremes of climate than
on the mainland ; and, most important of all, absolute freedom
from the competition of rival species. The flowers and their
insect inhabitants were all its own • there were no snakes or
mammalia to plunder its nests ; nothing to prevent the full
enjoyment of existence. The consequence would be, rapid
increase and a large permanent population, which still main-

1 See Macmillan's Magazine, September 1867, " On the Colours of Animals
and Plants," and chapters v. and vi., post.

HUMMING-BIRDS 327

tains itself ; for Mr. Moseley, of the Challenger expedition, has
informed the writer that humming-birds are extraordinarily
abundant in Juan Fernandez, every bush or tree having one
or two darting about it. Here, then, we have one of the
special conditions which have always been held to favour
variation — a great increase in the number of individuals ; but,
as there was no struggle with allied creatures, there was no
need for any modification in form or structure, and we accord-
ingly find that the only important variations which have
become permanent are those of size and of colour. The
increased size would naturally arise from greater abundance
of food with a more equable climate throughout the year ;
the healthier, stronger, and larger individuals being preserved.
The change of colour would depend on molecular changes in
the plumage accompanying the increase of size ; and the
superior energy and vitality in the male, aided by the favour-
able change in conditions and rapid increase of population,
would lead to an increased intensity of colour, the special tint
being determined either by local conditions or by inherited
tendencies in the race. It is to be noted that the change
from green to red is in the direction of the less refrangible
rays of the spectrum, and is in accordance with the law of
change which has been shown to accompany expansion in
inorganic growth and development in organic forms.1 The
change of colour in the female, not being urged on by such
intense vital activity as in the case of the male, would be
much slower, and, owing probably to inherited tendencies, in
a different direction. The under-surface of the Chilian bird
is ashy with bronzy-green spots on the breast, while the tail
is entirely bronze-green. In the Juan Fernandez species the
under-surface has become pure white, the breast-spots larger
and of a purer golden-green, while the whole inner web of the
tail-feathers has become pure white, producing a most elegant
effect when the tail is expanded.

We may now follow the two sexes to the remoter island,
at a period when the male had acquired his permanent style
of colouring, but was not quite so large as he subsequently
became ; while the change of the female bird had not been

1 See "Colours of Animals," MacmiUan's Magazine, September 1877, pp.
394-398, and chapter v., post.

TROPICAL NATURE

half completed. In this small and comparatively barren
island (a mere rock, as it is described by some authors) there
would be no such constant abundance of food, and therefore
no possibility of a large permanent population of humming-
birds; while the climate would not differ materially from
that of the larger island. Variation would therefore be
checked, or might be stopped altogether; and we find the
facts exactly correspond to this view. The male, which had
already acquired his colour, remains almost undistinguishable
from his immediate ancestral form ; but he is a little smaller,
indicating either that the full size of that form had not been
acquired at the period of migration, or that a slight diminution
of size has since occurred, owing to a deficiency of food. The
female shows also a slight diminution of size, but in other
respects is almost exactly intermediate between the Chilian and
Juan Fernandez females. The colour beneath is light ashy, the
breast-spots are intermediate in size and colour, and the tail-
feathers have a large ill-defined white spot on the end of the
inner web which has only to be extended along the whole web
to produce the exact character which has been acquired in
Juan Fernandez. It seems probable, therefore, that the
female bird has remained nearly or quite stationary since its
migration, while its Juan Fernandez relative has gone on
steadily changing in the direction already begun; and the
more distant species geographically thus appears to be more
nearly related to its Chilian ancestor.

Coming down to a more recent period, we find that the
comparatively small and dull-coloured Chilian bird has again
migrated to Juan Fernandez ; but it at once came into
competition with its red descendant, which had firm possession
of the soil, and had probably undergone slight constitutional
changes exactly fitting it to its insular abode. The new-
comer, accordingly, only just manages to maintain its footing ;
for we are told by Mr. Keed of Santiago that it is by no
means common ; whereas, as we have seen, the red species is
excessively abundant. We may further suspect that the
Chilian birds now pass over pretty frequently to Juan
Fernandez, and thus keep up the stock; for it must be
remembered that whereas, at a first migration, both a male
and a female are necessary for colonisation, yet, after a

HUMMING-BIRDS 329

colony is formed, any stray bird which may come over adds
to the numbers, and checks permanent variation by cross-
breeding.

We find, then, that all the chief peculiarities of the three
allied species of humming-birds which inhabit the Juan
Fernandez group of islands, may be fairly traced to the action
of those general laws which Mr. Darwin and others have
shown to determine the variation of animals and the per-
petuation of those variations. It is also instructive to note
that where the variations of colour and size have been greatest
they are accompanied by several lesser variations in other
characters. In the Juan Fernandez bird the bill has become
a little shorter, the tail feathers somewhat broader, and the
fiery cap on the head somewhat smaller ; all these peculiarities
being less developed or absent in the birds inhabiting Mas-
afuera. These coincident changes may be due, either to
what Mr. Darwin has termed correlation of growth, or to
the partial reappearance of ancestral characters under more
favourable conditions, or to the direct action of changes of
climate and of food ; but they show us how varied and un-
accountable are the changes in specific forms that may be
effected in a comparatively short time, and by means of very
slight changes of locality.

If now we consider the enormously varied conditions
presented by the whole continent of America — the hot, moist,
and uniform forest-plains of the Amazon ; the open llanos of
the Orinoco ; the dry uplands of Brazil ; the sheltered valleys
and forest slopes of the Eastern Andes ; the verdant plateaux,
the barren paramos, the countless volcanic cones with their
peculiar Alpine vegetation ; the contrasts of the east and
west coasts ; the isolation of the West Indian islands, and to
a less extent of Central America and Mexico, which we know
have been several times separated from South America ; and
when we further consider that all these characteristically
distinct areas have been subject to cosmical and local changes,
to elevations and depressions, to diminution and increase of
size, to greater extremes and greater uniformity of temper-
ature, to increase or decrease of rainfall ; and that with these
changes there have been coincident changes of vegetation and
of animal life, all affecting in countless ways the growth and

TROPICAL NATURE

development; the forms and colours, of these wonderful little

bir(js if we consider all these varied and complex influences,

we shall be less surprised at their strange forms, their infinite
variety, their wondrous beauty. For how many ages the
causes above enumerated may have acted upon them we
cannot say ; but their extreme isolation from all other birds,
no less than the abundance and variety of their generic and
specific forms, clearly point to a very high antiquity.

The Relations and Affinities of Humming-birds
The question of the position of this family in the class
of birds and its affinities or resemblances to other groups
is so interesting, and affords such good opportunities for
explaining some of the best established principles of classifica-
tion in natural history in a popular way, that we propose to
discuss it at some length, but without entering into technical
details.

There is in the Eastern hemisphere, especially in tropical
Africa and Asia, a family of small birds called sun-birds, which
are adorned with brilliant metallic colours, and which, in shape
and general appearance, much resemble humming-birds. They
frequent flowers in the same way, feeding on honey and insects ;
and all the older naturalists placed the two families side by
side as undoubtedly allied. In the year 1850, in a general
catalogue of birds, Prince Lucien Bonaparte, a learned
ornithologist, placed the humming-birds next to the swifts,
and far removed from the Nectarinidse or sun-birds ; and this
view of their position has gained ground with increasing
knowledge, so that now all the more advanced ornithologists
have adopted it. Before proceeding to point out the reasons
for this change of view, it will be well to discuss a few of the
general principles which guide naturalists in the solution of
such problems.

How to Determine doubtful Affinities

It is now generally admitted that, for the purpose of
determining obscure and doubtful affinities, we must examine
by preference those parts of an animal which have little or no
direct influence on its habits and general economy. The value
of an organ, or of any detail of structure, for purposes of

HUMMING-BIRDS 331

classification, is generally in inverse proportion to its adapt-
ability to special uses. And the reason of this is apparent,
when we consider that similarities of food and habits are often
accompanied by similarities of external form or of special
organs, in totally distinct animals. Porpoises, for example,
are modified externally so as to resemble fishes ; yet they are
really mammalia. Some marsupials are carnivorous, and are
so like true carnivora that it is only by minute peculiarities of
structure that the skeleton of the one can be distinguished
from that of the other. Many of the hornbills and toucans
have the same general form, and resemble each other in habits,
in food, and in their enormous bills ; yet peculiarities in the
structure of the feet, in the form of the breast-bone, in the
cranium, and in the texture and arrangement of the plumage,
show that they have no real affinity, the former approach-
ing the kingfishers, the latter the cuckoos. Such structural
peculiarities as these have no direct relation to habits ; and
they are therefore little liable to change, when from any cause
a portion of the group may have been driven to adopt a new
mode of life. Thus all the Old World apes, however much
they may differ in size or habits, and whether we class them
as baboons, monkeys, or anthropoids, have the same number
of teeth ; while the American monkeys all have an additional
premolar tooth. This difference can have no relation to the
habits of the two groups, because each group exhibits differ-
ences of habits greater than often occur between American
and Asiatic species.; and it thus becomes a valuable character
indicating the radical distinctness of the two groups, a distinct-
ness confirmed by other anatomical characters.

On the other hand, peculiarities of organisation which seem
specially adapted to certain modes of life are often diminished
or altogether lost in a few species of the group, showing their
essential unimportance to the type, as well as their small
value for classification. Thus the woodpeckers are most
strikingly characterised by a very long and highly extensible
tongue, with the muscles attached to the tongue-bone prolonged
backward over the head so as to enable the tongue to be
suddenly darted out ; and also by the rigid and pointed tail,
which is a great help in climbing up the vertical trunks of
trees. But in one group (the Picumni) the tail becomes quite

TROPICAL NATURE

soft, while the tongue remains fully developed ; and in another
(Meiglyptes) the characteristic tail remains, while the prolonged
hyoid muscles have almost entirely disappeared, and the
tongue has consequently lost its peculiar extensile power ; yet
in both these cases the form of the breast -bone and the
character of the feet, the skeleton, and the plumage, show that
the birds are really woodpeckers ; while even the habits and
the food are very little altered. In like manner the bill may
undergo great changes ; as from the short crow-like bill of the
true birds-of-paradise to the long slender bills of Epimachinse,
which latter were on that account long classed apart in the
tribe of Tenuirostres, or slender-billed birds, but whose entire
structure shows them to be closely allied to the paradise-birds.
So, the long feathery tongue of the toucans differs from that of
every other bird ; yet it is not held to overbalance the weight
of anatomical peculiarities which show that these birds are
allied to the barbets and the cuckoos.

The skeleton, therefore, and especially the sternum or
breast-bone, affords us an almost infallible guide in doubtful
cases; because it appears to change its form with extreme
slowness, and thus indicates deeper seated affinities than those
shown by organs which are in direct connection with the out-
side world, and are readily modified in accordance with varying
conditions of existence. Another, though less valuable guide
is afforded, in the case of birds, by the eggs. These often
have a characteristic form and colour, and a peculiar texture
of surface, running unchanged through whole genera and
families which are nearly related to each other, however much
they may differ in outward form and habits. Another detail
of structure, which has no direct connection with habits and
economy, is the manner in which the plumage is arranged on
the body. The feathers of birds are by no means set uni-
formly over their skin, but grow in certain definite lines and
patches, which vary considerably in shape and size in the more
important orders and tribes, while the mode of arrangement
agrees in all which are known to be closely related to each
other; and thus the form of the feather -tracts or the
" pterylography," as it is termed, of a bird, is a valuable aid
in doubtful cases of affinity.

Now, if we apply these three tests to the humming-birds,

HUMMING-BIRDS

we find them all pointing in the same direction. The sternum
or breastbone is not notched behind ; and this agrees with the
swifts, and not with the sun-birds, whose sternum has two deep
notches behind, as in all the families of the vast order of
Passeres to which the latter belong. The eggs of both swifts
and humming-birds are white, only two in number, and
resembling each other in texture. And in the arrangement
of the feather-tracts the humming-birds approach more nearly
to the swifts than they do to any other birds ; and altogether
differ from the sun-birds, which in this respect, as in so many
others, resemble the honey-suckers of Australia and other true
passerine birds.

Resemblances of Swifts and Humming-birds
Having this clue to their affinities, we shall find other
peculiarities common to these two groups, the swifts and the
humming-birds. They have both ten tail-feathers, while the
sun-birds have twelve. They have both only sixteen true
quill-feathers, and they are the only birds which have so
small a number. The humming-birds are remarkable for
having, in almost all the species, the first quill the longest of
all, the only other birds resembling them in this respect
being a few species of swifts ; and, lastly, in both groups
the plumage is remarkably compact and closely pressed to
the body. Yet, with all these points of agreement, we find
an extreme diversity in the bills and tongues of the two
groups. The swifts have a short, broad, flat bill, with a flat
horny -tipped tongue of the usual character; while the
humming-birds have a very long, narrow, almost cylindrical
bill, containing a tubular and highly extensible tongue. The
essential point, however, is, that whereas hardly any of the
other characters we have adduced are adaptive, or strictly
correlated with habits and economy, this character is pre-
eminently so ; for the swifts are pure aerial insect-hunters,
and their short, broad bills and wide gape are essential to
their mode of life. The humming-birds, on the other hand,
are floral insect-hunters, and for this purpose their peculiarly
long bills and extensile tongues are especially adapted ; while
they are at the same time honey-suckers, and for this purpose
have acquired the tubular tongue. The formation of such a

334 TROPICAL NATURE

tubular tongue out of one of the ordinary kind is easily con-
ceivable, as it only requires to be lengthened, and the two
laminae of which it is composed curled in at the sides ; and
these changes it probably goes through in the young birds.

When on the Amazons I once had a nest brought me
containing two little unfledged humming-birds, apparently
not long hatched. Their beaks were not at all like those
of their parents, but short, triangular, and broad at the base,
just the form of the beak of a swallow or swift slightly
lengthened. Thinking (erroneously) that the young birds
were fed by their parents on honey, I tried to feed them with
a syrup made of honey and water, but though they kept their
mouths constantly open as if ravenously hungry, they would
not swallow the liquid, but threw it out again and sometimes
nearly choked themselves in the effort. At length I caught
some minute flies, and on dropping one of these into the open
mouth it instantly closed, the fly was gulped down and the
mouth opened again for more; and each took in this way
fifteen or twenty little flies in succession before it was satis-
fied. They lived thus three or four days, but required more
constant care than I could give them. These little birds
were in the "swift" stage; they were pure insect-eaters,
with a bill and mouth adapted for insect- eating only. At
that time I was not aware of the importance of the observa-
tion of the tongue; but as the bill was so short and the
tubular tongue not required, there can be little doubt that
the organ was, at that early stage of growth, short and flat, as
it is in the birds most nearly allied to them.

Differences between Sun-birds and Humming-birds
In respect of all the essential and deep-seated points of
structure, which have been shown to offer such remarkable
similarities between the swifts and the humming-birds, the
sun-birds of the Eastern hemisphere differ totally from the
latter, while they agree with the passerine birds generally, or
more particularly with the creepers and honey-suckers. They
have a deeply-notched sternum ; they have twelve tail-feathers
in place of ten ; they have nineteen quills in place of sixteen ;
and the first quill instead of being the longest is the very
shortest of all, while the wings are short and round instead

HUMMING-BIRDS

of being excessively long and pointed; their plumage is
arranged differently; and their feet are long and strong,
instead of being excessively short and weak. There remain
only the superficial characters of small size and brilliant
metallic colours to assimilate them with the humming-birds,
and one structural feature — a tubular and somewhat extensile
tongue. This, however, is a strictly adaptive character, the
sun-birds feeding on small insects and the nectar of flowers,
just as do the humming-birds ; and it is a remarkable instance
of a highly peculiar modification of an organ occurring inde-
pendently in two widely-separated groups. In the sun-birds
the hyoid or tongue-muscles do not extend so completely over
the head as they do in the humming-birds, so that the tongue
is less extensible ; but it is constructed in exactly the same
way by the inrolling of the two laminae of which it is
composed.

The tubular tongue of the sun-birds is a special adaptive
modification acquired within the family itself, and not
inherited from a remote ancestral form. This is shown by
the amount of variation this organ exhibits in different mem-
bers of the family. It is most highly developed in the
Arachnotheras, or spider-hunters of Asia, which are sun-birds
without any metallic or other brilliant colouring. These
have the longest bills and tongues, and the most developed
hyoid muscles ; they hunt much about the blossoms of palm-
trees, and may frequently be seen probing the flowers while
fluttering clumsily in the air, just as if they had seen and
attempted to imitate the aerial gambols of the American
humming-birds. The true metallic sun-birds generally cling
about the flowers with their strong feet; and they feed
chiefly on minute hard insects, as do many humming-birds.
There is, however, one species (Chalcoparia phoenicotis),
always classed as a sun-bird, which differs entirely from the
rest of the species in having the tongue flat, horny, and forked
at the tip ; and its food seems to differ correspondingly, for
small caterpillars were found in its stomach. More remotely
allied, but yet belonging to the same family, are the little
flower-peckers of the genus Diceum, which have a short bill
and a tongue twice split at the end ; and these feed on small
fruits, and perhaps on buds and on the pollen of flowers. The

TROPICAL NATURE

little white-eyes (Zosterops), which are probably allied to the
last, eat soft fruits and minute insects.

Conclusion

Here, then, we have an extensive group of birds, consider-
ably varied in external form, yet undoubtedly closely allied
to each other, one division of which is specially adapted to
feed on the juices secreted by flowers and the minute insects
that harbour in them ; and these alone have a lengthened bill
and double tubular tongue, just as in the humming-birds.
We can hardly have a more striking example of the necessity
of discriminating between adaptive and purely structural
characters. The same adaptive character may coexist in two
groups which have a similar mode of life, without indicating
any affinity between them, because it may have been acquired
by each independently to enable it to fill a similar place in
nature. In such cases it is found to be an almost isolated
character, apparently connecting two groups which otherwise
differ radically. Non- adaptive or purely structural charac-
ters, on the other hand, are such as have probably been
transmitted from a remote ancestor, and thus indicate funda-
mental peculiarities of growth and development. The changes
of structure rendered necessary by modifications of the habits
or instincts of the different species have been made to a great
extent independently of such characters; and as several of
these may always be found in the same animal their value
becomes cumulative. We thus arrive at the seeming paradox
that the less of direct use is apparent in any peculiarity of
structure, the greater is its value in indicating true, though
perhaps remote, affinities ; while any peculiarity of an organ
which seems essential to its possessor's wellbeing is often of
very little value in indicating its affinity for other creatures.

This somewhat technical discussion will, it is hoped, enable
the general reader to understand some of the more important
principles of the modern or natural classification of animals as
distinguished from the artificial system which long prevailed.
It will also afford him an easily remembered example of those
principles, in the radical distinctness of two families of birds
often confounded together, — the sun -birds of the Eastern
Hemisphere and the humming - birds of America ; and in

HUMMING-BIRDS 337

the interesting fact that the latter are essentially swifts —
profoundly modified, it is true, for an aerial and flower-
haunting existence, but still bearing in many important
peculiarities of structure the unmistakable evidences of a

1 Recent researches into the anatomy of the swifts and humming-birds
have brought to light so many and such important differences that the above
conclusion, founded on comparatively superficial characters, becomes doubtful.
Dr. Shufeldt considers that both groups are so isolated that they each require
to be classed as a distinct order of birds. But while the swifts are believed
to have undoubted though remote affinities with the swallows, it cannot yet
be determined whether they have any real affinity with the humming-birds,
which latter appear to have no special and unmistakable relationship with
any other order or family of birds. See " Studies of the Macrochires, Mor-
phological, and otherwise, with the view of indicating their relationships," etc.,
by R. W. Shufeldt, M.D., in the Journal of the Linnean Society, vol. zx. ;
Zoology, pp. 299, 394 : 1889.

THE COLOURS OF ANIMALS AND SEXUAL SELECTION1

General Phenomena of Colour in the Organic World— Theory of Heat and
Light as producing Colour— Changes of Colour in Animals produced
by Coloured Light— Classification of Organic Colours— Protective
Colours— Warning Colours— Sexual Colours— Normal Colours— The
Nature of Colour— How Animal Colours are produced— Colour a
normal product of Organisation— Theory of Protective Colours-
Theory of Warning Colours— Imitative Warning Colours— The Theory
of Mimicry — Theory of Sexual Colours — Colour as a means of Recog-
nition— Colour proportionate to Integumentary Development — Selec-
tion by Females not a cause of Colour— Probable use of the Horns
of Beetles — Cause of the greater Brilliancy of some Female Insects —
Origin of the Ornamental Plumage of Male Birds— Theory of Display
of Ornaments by Males— Natural Selection as neutralising Sexual
Selection — Greater Brilliancy of some Female Birds — Colour-develop-
ment as illustrated by Humming-Birds — Theory of Normal Colours —
Local causes of Colour-development — The influence of Locality on
Colour in Butterflies and Birds — Sense -perception influenced by Colour
of the Integuments — Summary on Colour-development in Animals.

General Phenomena of Colour in the Organic World
THERE is probably no one quality of natural objects from
which we derive so much pure and intellectual enjoyment as
from their colours. The heavenly blue of the firmament, the
glowing tints of sunset, the exquisite purity of the snowy
mountains, and the endless shades of green presented by the
verdure-clad surface of the earth, are a never-failing source of
pleasure to all who enjoy the inestimable gift of sight. Yet
these constitute, as it were, but the frame and background of

1 A first sketch of this essay appeared in Macmillan's Magazine of Sep^
tember 1877,

v COLOURS OF ANIMALS 339

a marvellous and ever-changing picture. In contrast with
these broad and soothing tints, we have presented to us in
the vegetable and animal worlds an infinite variety of objects
adorned with the most beautiful and most varied hues.
Flowers, insects, and birds are the organisms most generally
ornamented in this way ; and their symmetry of form, their
variety of structure, and the lavish abundance with which
they clothe and enliven the earth, cause them to be objects
of universal admiration. The relation of this wealth of colour
to our mental and moral nature is indisputable. The child
and the savage alike admire the gay tints of flower, bird,
and insect ; while to many of us their contemplation brings a
solace and enjoyment which is both intellectually and morally
beneficial. It can then hardly excite surprise that this rela-
tion was long thought to afford a sufficient explanation of the
phenomena of colour in nature ; and although the fact that

Full many a flower is born to blush unseen,
And waste its sweetness on the desert air,

might seem to throw some doubt on the sufficiency of the
explanation, the answer was easy, — that in the progress of
discovery man would, sooner or later, find out and enjoy
every beauty that the hidden recesses of the earth have in
store for him. This theory received great support from the
difficulty of conceiving any other use or meaning in the
colours with which so many natural objects are adorned.
Why should the homely gorse be clothed in golden raiment,
and the prickly cactus be adorned with crimson bells ? Why
should our fields be gay with buttercups, and the heather-clad
mountains be clad in purple robes ? Why should every land
produce its own peculiar floral gems, and the alpine rocks
glow with beauty, if not for the contemplation and enjoyment
of man ? What could be the use to the butterfly of its gaily-
painted wings, or to the humming-bird of its jewelled breast,
except to add the final touches to a world-picture, calculated at
once to please and to refine mankind ? And even now, with all our
recently acquired knowledge of this subject, who shall say that
these old-world views were not intrinsically and fundamentally
sound; and that, although we now know that colour has "uses"
in nature that we little dreamt of, yet the relation of those
colours — or rather of the various rays of light — to our senses

340 TROPICAL NATURE

and emotions may not be another and perhaps more important
use which they subserve in the great system of the universe ?

We now propose to lay before our readers a general account
of the more recent discoveries on this interesting subject ; and
in doing so it will be necessary first to give an outline of the
more important facts as to the colours of organised beings ;
then to point out the cases in which it has been shown that
colour is of use ; and lastly, to endeavour to throw some light
on its nature and on the general laws of its development.

Among naturalists, colour was long thought to be of little
import, and to be quite untrustworthy as a specific character.
The numerous cases of variability of colour led to this view.
The occurrence of white blackbirds, white peacocks, and black
leopards, of white blue-bells, and of white, blue, or pink milk-
worts, led to the belief that colour was essentially unstable,
that it could therefore be of little or no importance, and
belonged to quite a different class of characters from form or
structure. But it now begins to be perceived that these
cases, though tolerably numerous, are, after all, exceptional ;
and that colour, as a rule, is a constant character. The great
majority of the species, both of animals and plants, are each
distinguished by peculiar tints which vary very little, while
the minutest markings are often constant in thousands or
millions of individuals. All our field buttercups are invari-
ably yellow, and our poppies red, while many of our butter-
flies and birds resemble each other in every spot and streak of
colour through thousands of individuals. We also find that
colour is constant in whole genera and other groups of species.
The Genistas are all yellow, the Erythrinas all red; many
genera of Carabidae are entirely black ; whole families of birds
— as the Dendrocolaptidse — are brown ; while among butter-
flies the numerous species of Lycsena are all more or less blue,
those of Pontia white, and those of Callidryas yellow. An ex-
tensive survey of the organic world thus leads us to the conclu-
sion that coloiir is by no means so unimportant or inconstant
a character as at first sight it appears to be ; and the more we
examine it the more convinced we shall become that it must
serve some purpose in nature, and that, besides charming us
by its diversity and beauty, it must be well worthy of our
attentive study, and have many secrets to unfold to us.

COLOURS OF ANIMALS • 341

Theory of Heat and Light as producing Colour
In commencing our study of the great mass of facts
relating to the colours of the organic world, it will be neces-
sary to consider, first, how far the chief theories already
proposed will account for them. One of the most obvious and
most popular of these theories, and one which is still held, in
part at least, by many eminent naturalists, is, that colour is
due to some direct action of the heat and light of the sun —
thus at once accounting for the great number of brilliant birds,
insects, and flowers which are found between the tropics.

But before proceeding to discuss this supposed explanation
of the colours of living things, we must ask the preliminary
question, — whether it is really the fact that colour is more
developed in tropical than in temperate climates in propor-
tion to the whole number of species ; and even if we find this
to be so, we have to inquire whether there are not so many
and such striking exceptions to the rule as to indicate some
other causes at work than the direct influence of solar light
and heat. As this is a most important branch of the inquiry,
we must go into it somewhat fully.

It is undoubtedly the case that there are an immensely
greater number of richly-coloured birds and insects in tropical
than in temperate and cold countries, but it is by no means
so certain that the proportion of coloured to obscure species is
much or any greater. Naturalists and collectors well know
that the majority of tropical birds are dull- coloured ; and
there are whole families, comprising hundreds of species, not
one of which exhibits a particle of bright colour. Such are,
for example, the Timaliidse or babbling thrushes of the eastern,
and the Dendrocolaptidae or tree-creepers of the western
hemispheres. Again, many groups of birds which are uni-
versally distributed are no more adorned with colour in the
tropical than in the temperate zones ; such are the thrushes,
wrens, goat-suckers, hawks, grouse, plovers, and snipe ; and if
tropical light and heat have any direct colouring effect, it is
certainly most extraordinary that in groups so varied in form,
structure, and habits as those just mentioned, the tropical
should be in no wise distinguished in this respect from the
temperate species.

342 TROPICAL NATURE

It is true that brilliant tropical birds mostly belong to
groups which are wholly tropical — as the chatterers, toucans,
trogons, and pittas ; but as there are perhaps an equal num-
ber of tropical groups which are wholly dull-coloured, while
others contain dull and bright-coloured species in nearly equal
proportions, the evidence is by no means strong that tropical
light and heat have anything to do with the matter. But
there are other groups in which the cold and temperate zones
produce finer -coloured species than the tropics. Thus the
arctic ducks and divers are handsomer than those of the
tropical zone ; while the king-duck of temperate America and
the mandarin-duck of North China are the most beautifully
coloured of the whole family. In the pheasant family we
have the gorgeous gold and silver pheasants in North China
and Mongolia, and the superb Impeyan pheasant in the tem-
perate North- Western Himalayas, as against the peacock and
fire -backed pheasants of tropical Asia. Then we have the
curious fact that most of the bright -coloured birds of the
tropics are denizens of the forests, where they are shaded
from the direct light of the sun, and that they abound near
the equator, where cloudy skies are very prevalent ; while, on
the other hand, places where light and heat are at a maxi-
mum have often dull -coloured birds. Such are the Sahara
and other deserts, where almost all the living things are
sand-coloured ; but the most curious case is that of the Gala-
pagos islands, situated under the equator, and not far from
South America, where the most gorgeous colours abound, but
which are yet characterised by prevailing dull and sombre
tints in birds, insects, and flowers, so that they reminded Mr.
Darwin of the cold and barren plains of Patagonia rather
than of any tropical country. Insects are wonderfully
brilliant in tropical countries generally, and any one looking
over a collection of South American or Malayan butterflies
would scout the idea of their being no more gaily -coloured
than the average of European species, and in this he would
be undoubtedly right. But on examination we should find
that all the more brilliantly-coloured groups were exclusively
tropical, and that where a genus has a wide range there is
little difference in coloration between the species of cold and
warm countries. Thus the European Vanessides, including

v COLOURS OF ANIMALS 343

the beautiful "peacock," "Camberwell beauty," and "red
admiral" butterflies, are quite up to the average of tropi-
cal colour in the same group ; and the remark will equally
apply to the little " blues " and " coppers " ; while the alpine
" apollo " butterflies have a delicate beauty that can hardly
be surpassed. In other insects, which are less directly
dependent on climate and vegetation, we find even greater
anomalies. In the immense family of the Carabidae or pre-
daceous ground -beetles, the northern forms fully equal, if
they do not surpass, all that the tropics can produce. Every-
where, too, in hot countries, there are thousands of obscure
species of insects which, if they were all collected, would not
improbably bring down the average of colour to much about
the same level as that of temperate zones.

But it is when we come to the vegetable world that the
greatest misconception on this subject prevails. In abund-
ance and variety of floral colour the tropics are almost univer-
sally believed to be pre-eminent, not only absolutely, but
relatively to the whole mass of vegetation and the total
number of species. Twelve years of observation among the
vegetation of the eastern and western tropics has, however,
convinced me that this notion is entirely erroneous, and that,
in proportion to the whole number of species of plants, those
having gaily-coloured flowers are actually more abundant in
the temperate zones than between the tropics. This will be
found to be not so extravagant an assertion as it may at first
appear, if we consider how many of the choicest adornments
of our greenhouses and flower-shows are really temperate as
opposed to tropical plants. The masses of colour produced by
our rhododendrons, azaleas, and camellias, our pelargoniums,
calceolarias, and cinerarias — all strictly temperate plants —
can certainly not be surpassed, if they can be equalled, by any
productions of the tropics.

It may be objected that most of the plants named are
choice cultivated varieties, far surpassing in colour the original
stock, while the tropical plants are mostly unvaried wild
species. But this does not really much affect the question at
issue. For our florists' gorgeous varieties have all been pro-
duced under the influence of our cloudy skies, and with even
a still further deficiency of light, owing to the necessity of

344 TROPICAL NATURE

protecting them under glass from our sudden changes of
temperature, so that they are themselves an additional proof
that tropical light and heat are not needed for the production
of intense and varied colour. Another important considera-
tion is, that these cultivated varieties in many cases displace a
number of wild species which arc hardly, if at all, cultivated.
Thus there are scores of species of wild hollyhocks varying in
colour almost as much as the cultivated varieties, and the
same may be said of the pentstemons, rhododendrons, and
many other flowers ; and if these were all brought together
in well-grown specimens, they would produce a grand effect.
But it is far easier, and more profitable for our nurserymen,
to grow varieties of one or two species, which all require a
similar culture, rather than fifty distinct species, most of
which would require special treatment, the result being that
the varied beauty of the temperate flora is even now hardly
known, except to botanists and to a few amateurs.

But we may go further, and say that the hardy plants of
our cold temperate zone equal, if they do not surpass, the
productions of the tropics. Let us only remember such
gorgeous tribes of flowers as the roses, pseonies, hollyhocks,
and antirrhinums; the laburnum, wistaria, and lilac; the
lilies, irises, and tulips; the hyacinths, anemones, gentians,
and poppies, and even our humble gorse, broom, and heather ;
and we may defy any tropical country to produce masses of
floral colour in greater abundance and variety. It may be
true that individual tropical shrubs and flowers do surpass
everything in the rest of the world ; but that is to be expected,
because the tropical zone comprises a much greater land area
than the two temperate zones, while, owing to its more
favourable climate, it produces a still larger proportion of
species of plants and a greater number of peculiar natural
orders.

Direct observation in tropical forests, plains, and mountains
fully supports this view. Occasionally we are startled by
some gorgeous mass of colour, but as a rule we gaze upon an
endless expanse of green foliage, only here and there enlivened
by not very conspicuous flowers. Even the orchids, whose
superb blossoms adorn our stoves, form no exception to
this rule. It is only in favoured spots that we find them in

v COLOURS OF ANIMALS 345

abundance j the species with small and inconspicuous flowers
greatly preponderate ; and the flowering season of each kind
being of short duration, they rarely produce any marked
effect of colour amid the vast masses of foliage which sur-
round them. An experienced collector in the Eastern tropics
once told me that although a single mountain in Java had
produced three hundred species of Orchidese, only about 2
per cent of the whole were sufficiently ornamental or showy
to be worth sending home as a commercial speculation. The
Alpine meadows and rock-slopes, the open plains of the Cape
of Good Hope or of Australia, and the flower -prairies of
North America, offer an amount and variety of floral colour
which can certainly not be surpassed, even if it can be
equalled, between the tropics.

It appears, therefore, that we may dismiss the theory that
the development of colour in nature is directly dependent on,
and in any way proportioned to, the amount of solar heat and
light, as entirely unsupported by facts. Strange to say, how-
ever, there are some rare and little-known phenomena which
prove that in exceptional cases light does directly affect the
colours of natural objects, and it will be as well to consider
these before passing on to other matters.

Changes of Colour in Animals produced by Coloured Light
A few years ago Mr. T. W. Wood called attention to the
curious changes in the colour of the chrysalis of the small
cabbage -butterfly (Pontia rapse) when the caterpillars, just
before their change, were confined in boxes lined with
different tints. Thus in black boxes they were very dark, in
white boxes nearly white ; and he further showed that similar
changes occurred in a state of nature, chrysalises fixed against
a whitewashed wall being nearly white, against a red brick
wall reddish, against a pitched pailing nearly black. It has
also been observed that the cocoon of the emperor-moth is
either white or brown, according to the colours surrounding
it. But the most extraordinary example of this kind of
change is that furnished by the chrysalis of an African
butterfly (Papilio Nireus), observed at the Cape by Mrs.
Barber, and described (with a coloured plate) in the Transac-
tions of the Entomological Society, 1874, p. 519.

346 TROPICAL NATURE

This caterpillar feeds upon the orange tree, and also upon
a forest tree (Vepris lanceolata) which has a lighter green
leaf ; and its colour corresponds with that of the leaves it
feeds upon, being of a darker green when it feeds on the
orange. The chrysalis is usually found suspended among the
leafy twigs of its food-plant, or of some neighbouring tree,
but it is probably often attached to larger branches ; and Mrs.
Barber has discovered that it has the property of acquiring
the colour, more or less accurately, of any natural object it
may be in contact with. A number of the caterpillars were
placed in a case with a glass cover, one side of the case being
formed by a red brick wall, the other sides being of yellowish
wood. They were fed on orange leaves, and a branch of the
bottle -brush tree (Banksia sp.) was also placed in the case.
When fully fed, some attached themselves to the orange
twigs, others to the bottle-brush branch, and these all changed
to green pupae, but each corresponded exactly in tint to the
leaves around it, the one being dark, the other a pale faded
green. Another attached itself to the wood^ and the pupa
became of the same yellowish colour, while one fixed itself
just where the wood and brick joined, and became one side
red, the other side yellow ! These remarkable changes would
perhaps not have been credited had it not been for the pre-
vious observations of Mr. Wood ; but the two support each
other, and oblige us to accept them as actual phenomena. It
is a kind of natural photography, the particular coloured rays
to which the fresh pupa is exposed in its soft, semi-transparent
condition effecting such a chemical change in the organic
juices as to produce the same tint in the hardened skin. It
is interesting, however, to note that the range of colour that
can be acquired seems to be limited to those of natural
objects to which the pupa is likely to be attached, for when
Mrs. Barber surrounded one of the caterpillars with a piece
of scarlet cloth no change of colour at all was produced, the
pupa being of the usual green tint, but the small red spots
with which it is marked were brighter than usual. 1

1 Mr. E. B. Poulton has since greatly extended these observations, both in
pupae and larvae, with very remarkable results. See Proc. of the Royal
Society, No. 243, 1886 ; Transactions of the Royal Society, vol. clxxviii. B.,
pp. 311-441. These are briefly described in Darwinism, p. 197, and more
fully in a volume by Mr. Poulton on The Colours of Animals, 1890.

v COLOURS OF ANIMALS 847

Many other cases are known among insects in which the
same species acquires a different tint according to its sur-
roundings; this being particularly marked in some South
African locusts, which correspond with the colour of the soil
wherever they are found. There are also many caterpillars
which feed on two or more plants, and which vary in colour
accordingly. A number of such changes are quoted by Mr.
E. Meldola, in a paper on " Variable Protective Colouring in
Insects" (Proceedings of the Zoological Society of London, 1873,
p. 153); and in some cases it has been shown that green
chlorophyll remains unchanged in the tissues of leaf -eating
insects, and being discernible through the transparent
integument, produces the same colour as that of the food
plant.

In all these insects, as well as in the great majority of
cases in which a change of colour occurs in other animals, the
action is quite involuntary; but among some few of the
higher animals the colour of the integument can be modified
at the will of the individual, or at all events by a reflex
action dependent on sensation. The most remarkable case of
this kind occurs with the chameleon, which has the power of
changing its colour from dull white to a variety of tints.
This singular power has been traced to two layers of movable
pigment-cells deeply seated in the skin, but capable of being
brought near to the surface. The pigment-layers are bluish
and yellowish, and by their contraction or concentration these
can be forced upwards either together or separately. When
the animal is passive the colour is dirty white, which changes
to various tints of bluish, green, yellow, or brown, as more or
less of either pigment is forced up and rendered visible.
The animal is excessively sluggish and defenceless, and its
power of changing its colour so as to harmonise with sur-
rounding objects is essential to its safety. Here too, as with
the pupa of Papilio Nireus, colours such as scarlet or blue,
which do not occur in the natural environment of the animal,
cannot be produced. Somewhat similar changes of colour
occur in some prawns and flat-fish, according to the colour
of the bottom on which they rest. This is very striking
in the chameleon shrimp (Mysis chamseleon), which is
gray when on sand, but brown or green when among sea-

348 TROPICAL NATURE

weed of these two colours. Experiment shows, however,
that when blinded the change does not occur; so that
here too we probably have a voluntary or reflex sense-
action.

These peculiar powers of change of colour and adaptation
are, however, rare and quite exceptional. As a rule there is
no direct connection between the colours of organisms and
the kind of light to which they are usually exposed. This is
well seen in most fishes, and in such marine animals as por-
poises, whose backs are always dark, although this part is
exposed to the blue and white light of the sky and clouds,
while their bellies are very generally white, although these
are constantly subjected to the deep blue or dusky green
light from the bottom. It is evident, however, that these
two tints have been acquired for concealment and protection.
Looking down on the dark back of a fish it is almost invisible,
while, to an enemy looking up from below, the light under-
surface would be equally invisible against the light of the
clouds and sky. Again, the gorgeous colours of the butter-
flies which inhabit the depths of tropical forests bear no
relation to the kind of light that falls upon them, coming as
it does almost wholly from green foliage, dark brown soil,
or blue sky; and the bright under wings of many moths,
which are only exposed at night, contrast remarkably
with the sombre tints of the upper wings, which are
more or less exposed to the various colours of surrounding
nature.

Classification of Organic Colours

We find, then, that neither the general influence of solar
light and heat, nor the special action of variously tinted rays,
are adequate causes for the wonderful variety, intensity, and
complexity of the colours that everywhere meet us in the
animal and vegetable worlds. Let us therefore take a wider
view of these colours, grouping them into classes determined
by what we know of their actual uses or special relations to
the habits of their possessors. This, which may be termed
the functional and biological classification of the colours of
living organisms, seems to be best expressed by a division
into five groups, as follows : —

v COLOURS OF ANIMALS 349

{1. Protective colours.
2. Wamingcoloun. { J gSSBCSSSBi, ..
3. Sexual colours.
4. Normal colours.1
Plants 5. Attractive colours.

It is now proposed, firstly, to point out the nature of the
phenomena presented under each of these heads; then to
explain the general laws of the production of colour in
nature ; and, lastly, to show how far the varied phenomena
of animal coloration can be explained by means of those
laws, acting in conjunction with the laws of evolution and
natural selection.

Protective Colours

The nature of the two first groups, protective and warn-
ing colours, has been so fully detailed and illustrated in my
chapter on "Mimicry and other Protective Eesemblances
among Animals," that very little need be added here except
a few words of general explanation. Protective colours are
exceedingly prevalent in nature, comprising those of all the
white arctic animals, the sandy -coloured desert forms, and
the green birds and insects of tropical forests. It also com-
prises thousands of cases of special resemblance — of birds to
the surroundings of their nests, and especially of insects to
the bark, leaves, flowers, or soil, on or amid which they
dwell. Mammalia, fishes, and reptiles, as well as mollusca
and other marine invertebrates, present similar phenomena;
and the more the habits of animals are investigated, the more
numerous are found to be the cases in which their colours
tend to conceal them, either from their enemies or from the
creatures they prey upon. One of the last -observed and
most curious of these protective resemblances has been com-
municated to me by Sir Charles Dilke. He was shown in
Java a pink -coloured Mantis which, when at rest, exactly
resembled a pink orchis-flower. The mantis is a carnivorous
insect which lies in wait for its prey ; and, by its resemblance
to a flower, the insects it feeds on would be actually attracted
towards it. This one is said to feed especially on butter-

1 Many, or perhaps all, of these are now believed to be diversely coloured
for purposes of recognition. See Darwinism, p. 217.

350 TROPICAL NATURE

flies, so that it is really a living trap, and forms its own
bait!1

All who have observed animals, and especially insects, in
their native haunts and attitudes, can understand how it is
that an insect which in a cabinet looks exceedingly con-
spicuous, may yet when alive, in its peculiar attitude of
repose and with its habitual surroundings, be perfectly well
concealed. We can hardly ever tell by the mere inspection
of an animal whether its colours are protective or not. No
one would imagine the exquisitely beautiful caterpillar of the
emperor-moth, which is green with pink star-like spots, to be
protectively coloured ; yet, when feeding on the heather, it
so harmonises with the foliage and flowers as to be almost
invisible. Every day fresh cases of protective colouring are
being discovered, even in our own country; and it is becoming
more and more evident that the need of protection has played
a very important part in determining the actual coloration
of animals.

Warning Colours

The second class — the warning colours — are exceedingly
interesting, because the object and effect of these is, not to
conceal the object, but to make it conspicuous. To these
creatures it is useful to be seen and recognised ; the reason
being that they have a means of defence which, if known,
will prevent their enemies from attacking them, though it is
generally not sufficient to save their lives if they are actually
attacked. The best examples of these specially protected
creatures consist of two extensive families of butterflies, the
Danaidse and Acrseidse, comprising many hundreds of species
inhabiting the tropics of all parts of the world. These
insects are generally large, are all conspicuously and often
most gorgeously coloured, presenting almost every conceivable
tint and pattern ; they all fly slowly, and they never attempt
to conceal themselves ; yet no bird, spider, lizard, or monkey
(all of which eat other butterflies) ever devours them. The
reason simply is that they are not fit to eat, their juices
having a powerful odour and taste that is absolutely dis-
gusting to all these animals. Now we see the reason of their

1 These cases form a distinct sub-group of "alluring coloration." See
Dancinism, p. 210.

v COLOURS OF ANIMALS 351

showy colours and slow flight. It is good for them to be
seen and recognised, for then they are never molested ; but
if they did not differ in form and colouring from other
butterflies, or if they flew so quickly that their peculiarities
could not be easily noticed, they would be captured, and
though not eaten would be maimed or killed.

As soon as the cause of the peculiarities of these butterflies
was clearly recognised, it was seen that the same explanation
applied to many other groups of animals. Thus, bees and
wasps and other stinging insects are showily and distinctively
coloured ; many soft and apparently defenceless beetles, and
many gay-coloured moths, were found to be as nauseous as the
above-named butterflies ; other beetles, whose hard and glossy
coats of mail render them unpalatable to insect-eating birds,
are also sometimes showily coloured ; and the same rule was
found to apply to caterpillars, all the brown and green (or
protectively coloured species) being greedily eaten by birds,
while showy kinds which never hide themselves — like those
of the magpie-, mullein-, and burnet- moths — were utterly
refused by insectivorous birds, lizards, frogs, and spiders
(p. 84). Some few analogous examples are found among
vertebrate animals. I will only mention here a very interest-
ing case not given in my former work. In his delightful
book, entitled The Naturalist in Nicaragua, Mr. Belt tells us
that there is in that country a frog which is very abundant,
which hops about in the day-time, which never hides him-
self, and which is gorgeously coloured with red and blue.
Now frogs are usually green, brown, or earth-coloured, feed
mostly at night, and are all eaten by snakes and birds.
Having full faith in the theory of protective and warning
colours, to which he had himself contributed some valuable
facts and observations, Mr. Belt felt convinced that this frog
must be uneatable. He therefore took one home, and threw
it to his ducks and fowls ; but all refused to touch it except
one young duck, which took the frog in its mouth, but
dropped it directly, and went about jerking its head as if
trying to get rid of something nasty. Here the uneatableness
of the frog was predicted from its colours and habits, and we
can have no more convincing proof of the truth of a theory
than such previsions.

352 TROPICAL NATURE

The universal avoidance by carnivorous animals of all
these specially protected groups, which are thus entirely free
from the constant persecution suffered by other creatures not
so protected, would evidently render it advantageous for
any of these latter which were subjected to extreme persecu-
tion to be mistaken for the former ; and for this purpose it
would be necessary that they should have the same colours,
form, and habits. Now, strange to say, wherever there is
a large group of directly-protected forms (division a of animals
with warning colours), there are sure to be found a few other-
wise defenceless creatures which resemble them externally so
as to be mistaken for them, and which thus gain protection,
as it were, on false pretences (division b of animals with
warning colours). This is what is called " mimicry," and it
has already been very fully treated of by Mr. Bates (its dis-
coverer), by myself, by Mr. Trimen, and others. Here it is
only necessary to state that the uneatable Danaidae and
Acraeidae are accompanied by a few species of other groups
of butterflies (Leptalidse, Papilios, Diademas, and Moths),
which are all really eatable, but which escape attack by their
close resemblance to some species of the uneatable groups
found in the same locality. In like manner there are a few
eatable beetles which exactly resemble species of uneatable
groups ; and others, which are soft, imitate those which are
uneatable through their hardness. For the same reason
wasps are imitated by moths, and ants by beetles ; and even
poisonous snakes are mimicked by harmless snakes, and
dangerous hawks by defenceless cuckoos. How these curious
Imitations have been brought about, and the laws which
govern them, have been already discussed. (See p. 54.)

Sexual Colours

The third class comprises all cases in which the colours of
the two sexes differ. This difference is very general, and
varies greatly in amount, from a slight divergence of tint up
to a radical change of coloration. Differences of this kind
are found among all classes of animals in which the sexes are
separated, but they are much more frequent in some groups
than in others. In mammalia, reptiles, and fishes, they are

COLOURS OF ANIMALS

comparatively rare and not great in amount, whereas among
birds they are very frequent and very largely developed. So
among insects, they are abundant in butterflies, while they are
comparatively uncommon in beetles, wasps, and hemiptera.

The phenomena of sexual variations of colour, as well as of
colour generally, are wonderfully similar in the two analogous
yet totally unrelated groups of birds and butterflies ; and as
they both offer ample materials, we shall confine our study of
the subject chiefly to them. The most common case of differ-
ence of colour between the sexes is for the male to have the
same general hue as the females, but deeper and more intensi-
fied— as in many thrushes, finches, and hawks, and among
butterflies in the majority of our British species. In cases
where the male is smaller the intensification of colour is
especially well pronounced — as in many of the hawks and
falcons, and in most butterflies and moths in which the
coloration does not materially differ. In another extensive
series we have spots or patches of vivid colour in the male,
which are represented in the female by far less brilliant tints
or are altogether wanting — as exemplified in the gold-crest
warbler, the green woodpecker, and most of the orange-tip
butterflies (Anthocharis). Proceeding with our survey, we
find greater and greater differences of colour in the sexes, till
we arrive at such extreme cases as some of the pheasants, the
chatterers, tanagers, and birds-of-paradise, in which the male
is adorned with the most gorgeous and vivid colours, while
the female is usually dull brown, or olive green, and often
shows no approximation whatever to the varied tints of her
partner. Similar phenomena occur among butterflies ; and in
both these groups there are also a considerable number of
cases in which both sexes are highly but differently coloured.
Thus many woodpeckers have the head in the male red, in
the female yellow ; while some parrots have red spots in the
male, replaced by blue in the female, as in Psittacula diop-
thalma. In many South American Papilios, green spots on
the male are represented by red on the female ; and in several
species of the genus Epicalia, orange bands in the male are
replaced by blue in the female, a similar change of colour to
that in the small parrot above referred to. For fuller details
of the varieties of sexual coloration we refer our readers to
2 A.

354 TROPICAL NATURE

Mr. Darwin's Descent of Man, chapters x. to xviii., and to
chapters iii. iv. and vii. of the first portion of the present
volume.

Normal Colours

The fourth group — of normally coloured animals — includes
all species which are brilliantly or conspicuously coloured in
both sexes, and for whose particular colours we can assign no
function or use.1 It comprises an immense number of showy
birds, such as kingfishers, barbets, toucans, lories, tits, and
starlings ; among insects most of the largest and handsomest
butterflies, innumerable bright-coloured beetles, locusts, dragon-
flies, and hymenoptera ; a few mammalia, as the zebras ; a
great number of marine fishes ; thousands of striped and
spotted caterpillars ; and abundance of mollusca, star-fish, and
other marine animals. Among these we have included some
which, like the gaudy caterpillars, have warning colours ; but
as that theory does not explain the particular colours or the
varied patterns with which they are adorned, it is best to
include them also in this class. It is a suggestive fact that
all the brightly-coloured birds mentioned above build in holes
or form covered nests, so that the females do not need that
protection during the breeding season which I believe to be
one of the chief causes of the dull colour of female birds when
their partners are gaily coloured. This subject is fully argued
in chapter vi. of the present volume.

Leaving the colours of flowers to be discussed in another
chapter, we will now consider how the general facts of colour
here sketched out can be explained. We have first to inquire
what is colour, and how it is produced j secondly, what is
known of the causes of change of colour ; and, lastly, what
theory best accords with the whole assemblage of facts.

The Nature of Colour

The sensation of colour is caused by vibrations or undula-
tions of the ethereal medium of different lengths and velocities.
The whole body of vibrations caused by the sun is termed

* Distinctness of marking for purposes of recognition is probably the use
in all cases. See p. 367, and Darwinism, p. 217.

v COLOURS OF ANIMALS 355

radiation, or, more commonly, rays ; and consists of sets of
waves which vary considerably in their dimensions and rate
of recurrence, but of which the middle portion only is capable
of exciting in us sensations of light and colour. Beginning
with the largest waves, which recur at the longest intervals,
we have first those which produce heat-sensations only ; as
they get smaller and recur quicker, we perceive a dull red
colour ; and as the waves increase in rapidity and diminish in
size, we get successively sensations of orange, yellow, green,
blue, indigo, and violet, all fading imperceptibly into each
other. Then come more invisible rays, of shorter wave-
length and quicker recurrence, which produce, solely or
chiefly, chemical effects. The red rays, which first become
visible, have been ascertained to recur at the rate of 458
millions of millions times in a second, the length of each wave
being ?6^60- of an inch ; while the violet rays, which last
remain visible, recur 727 millions of millions times per second,
and have a wave-length of a^lfl of an inch. Although the
waves recur at different rates, they are all propagated through
the ether with the same velocity (192,000 miles per second) ;
just as different musical sounds, which are produced by
waves of air of different lengths and rates of recurrence, travel
at the same speed, so that a tune played several hundred
yards off reaches the ear in correct time. There are, there-
fore, an almost infinite number of different colour-producing
undulations, and these may be combined in an almost infinite
variety of ways, so as to excite in us the sensation of all the
varied colours and tints we are capable of perceiving. When
all the different kinds of rays reach us in the proportion in
which they exist in the light of the sun, they produce the
sensation of white. If the rays which excite the sensation of
any one colour are prevented from reaching us, the remaining
rays in combination produce a sensation of colour often very
far removed from white. Thus green rays being abstracted
leave purple light; blue, orange-red light; violet, yellowish-
green light, and so on. These pairs are termed comple-
mentary colours. And if portions of differently coloured
lights are abstracted in various degrees, we have produced all
those infinite gradations of colours, and all those varied tints
and hues which are of such use to us in distinguishing

356 TROPICAL NATURE

external objects, and which form one of the great charms of
our existence. Primary colours would therefore be as
numerous as the different wave-lengths of the visible radia-
tions, if we could appreciate all their differences; while
secondary or compound colours, caused by the simultaneous
action of any combination of rays of different wave-lengths,
must be still more numerous.

In order to account for the fact that all colours appear to
us to be produced by combinations of three primary colours
— red, green, and violet — it is believed that we have three
sets of nerve fibres in the retina, each of which is capable of
being excited by all rays, but that one set is excited most by
the larger or red waves, another by the medium or green
waves, and the third set chiefly by the violet or smallest
waves of light ; and when all three sets are excited together
in proper proportions we see white. This view is supported
by the phenomena of colour-blindness, which are explicable on
the theory that one of these sets of nerve-fibres (usually that
adapted to perceive red) has lost its sensibility, causing all
colours to appear as if the red rays were abstracted from
them.

It is a property of these various radiations that they are
unequally refracted or bent in passing obliquely through
transparent bodies, the longer waves being least refracted, the
shorter most. Hence it becomes possible to analyse white or
any other light into its component rays. A small ray of
sunlight, for example, which would produce a white spot
on a wall, if passed through a prism, is lengthened out into a
band of coloured light, exactly corresponding to the colours of
the rainbow. Any one colour can thus be isolated and
separately examined ; and by means of reflecting mirrors the
separate colours can be again compounded in various ways,
and the resulting colours observed. This band of coloured
light is called a spectrum, and the instrument by which the
spectra of various kinds of light are examined is called a
spectroscope. This branch of the subject has, however, no
direct bearing on the mode in which the colours of living
things are produced, and it has only been alluded to in order
to complete our sketch of the nature of colour.

The colours which we perceive in material substances are

v COLOURS OF ANIMALS 857

produced either by the absorption or by the interference of
some of the rays which form white light. Pigmental or
absorption-colours are the most frequent, comprising all the
opaque tints of flowers and insects, and all the colours of dyes
and pigments. They are caused by rays of certain wave-
lengths being absorbed, while the remaining rays are reflected
and give rise to the sensation of colour. When all the colour-
producing rays are reflected in due proportion, the colour of
the object is white ; when all are absorbed the colour is black.
If blue rays only are absorbed the resulting colour is orange-
red ; and generally, whatever colour an object appears to us,
it is because the complementary colours are absorbed by it.
The reason why rays of only certain refrangibilities are re-
flected, and the rest of the incident light absorbed by each
substance, is supposed to depend upon the molecular structure
of the body. Chemical action almost always implies change
of molecular structure; hence chemical action is the most
potent cause of change of colour. Sometimes simple solution
in water effects a marvellous change, as in the case of the
well-known aniline dyes; the magenta and violet dyes
exhibiting, when in the solid form, various shades of golden
or bronzy metallic green.

Heat alone often produces change of colour without effect-
ing any chemical change. Mr. Ackroyd has investigated this
subject,1 and has shown that a large number of bodies are
changed by heat, returning to their normal colour when
cooled, and that this change is almost always in the direction
of the less refrangible rays or longer wave-lengths; and he
connects the change with the molecular expansion caused by
heat. As examples may be mentioned mercuric oxide, which
is orange yellow, but which changes to orange, red, and brown
when heated ; chromic oxide, which is green, and changes to
yellow ; cinnabar, which is scarlet, and changes to puce ; and
metaborate of copper, which is blue, and changes to green
and greenish yellow.

How Animal Colours are Produced

The colouring matters of animals are very varied. Copper
has been found in the red pigment of the wing of the turaco,
1 " Metachromatism, or Colour-Change," Chemical News, August 1876.

358 TROPICAL NATURE

and Mr. Sorby has detected no less than seven distinct
colouring matters in birds' eggs, several of which are chem-
ically related to those of blood and bile. The same colours
are often produced by quite different substances in different
groups, as shown by the red of the wing on the burnet-moth
changing to yellow with muriatic acid, while the red of the
red-admiral butterfly undergoes no such change.

These pigmental colours have a different character in
animals according to their position in the integument. Fol-
lowing Dr. Hagen's classification, epidermal colours are those
which exist in the external chitinised skin of insects, in the
hairs of mammals, and, partially, in the feathers of birds.
They are often very deep and rich, and do not fade after
death. The hypodermal colours are those which are situated
in the inferior soft layer of the skin. These are often of
lighter and more vivid tints, and usually fade after death.
Many of the reds and yellows of butterflies and birds belong
to this class, as well as the intensely vivid hues of the naked
skin about the heads of many birds. These pigments some-
times exude through the pores, forming an evanescent bloom
on the surface.

Interference colours are less frequent in the organic world.
They are caused in two ways : either by reflection from the
two surfaces of transparent films, as seen in the soap-bubble
and in thin films of oil on water ; or by fine striae which pro-
duce colours either by reflected or transmitted light, as seen
in mother-of-pearl and in finely-ruled metallic surfaces. In
both cases colour is produced by light of one wave-length
being neutralised, owing to one set of such waves being
retarded or shifted so as to be half a wave-length behind the
other set, as may be found explained in any treatise on
physical optics. The result is, that the complementary colour
of that neutralised is seen ; and, as the thickness of the film or
the fineness of the striae undergo slight changes, almost any
colour can be produced. This is believed to be the origin of
many of the glossy or metallic tints of insects, as well as
those of the feathers of some birds. The iridescent colours of
the wings of dragon-flies are caused by the superposition of
two or more transparent lamellae ; while the shining blue of
the purple-emperor and other butterflies, and the intensely

v COLOURS OF ANIMALS 359

metallic colours of humming-birds, are probably due to fine
striae.

Colour a Normal Product of Organisation
This outline sketch of the nature of colour in the animal
world, however imperfect, will at least serve to show us how
numerous and varied are the causes which perpetually tend
to the production of colour in animal tissues. If we consider
that in order to produce white all the rays which fall upon an
object must be reflected in nearly the same proportions as
they exist in solar light — whereas, if rays of any one or more
kinds are absorbed or neutralised, the resultant reflected light
will be coloured ; and that this colour may be infinitely
varied according to the proportions in which different rays are
reflected or absorbed — we should expect that white would be,
as it really is, comparatively rare and exceptional in nature.1
The same observation will apply to black, which arises from
the absorption of all the different rays. Many of the com-
plex substances which exist in animals and plants are subject
to changes of colour under the influence of light, heat,
or chemical change, and we know that chemical changes
are continually occurring during the physiological processes
which occur in the body during development and growth.
We also find that every external character is subject to
minute changes, which are generally perceptible to us in
closely allied species ; and we can therefore have no doubt
that the extension and thickness of the transparent lamellae,
and the fineness of the striae or rugosities of the integuments,
must be undergoing constant minute changes ; and these
changes will very frequently produce changes of colour. These
considerations render it probable that colour is a normal and
even necessary result of the complex structure of animals and
plants ; and that those parts of an organism which are under-
going continual development and adaptation to new conditions,
and are also continually subject to the action of light and heat,
will be the parts in which changes of colour will most fre-
quently appear. Now there is little doubt that the external
changes of animals and plants in adaptation to the environ-

1 White is produced by the scattering of the various rays in all directions,
and is often caused by air-bubbles or transparent globules. See Poulton's
Colours of Animals, pp. 3-6.

TROPICAL NATURE

ment are much more numerous than the internal changes ; as
seen in the varied character of the integuments and append-
ages of animals — hair, horns, scales, feathers, etc., etc. — and
in plants, the leaves, bark, flowers, and fruit, with their
various modifications — as compared with the great uniformity
in the texture and composition of their internal tissues ; and
this accords with the uniformity of the tints of blood, muscle,
nerve, and bone throughout extensive groups, as compared
with the great diversity of colour of their external organs..
It seems a fair conclusion that colour per se may be considered
to be normal, and to need no special accounting for ; while
the absence of colour (that is, either white or black}, or the
prevalence of certain colours to the constant exclusion of
others, must be traced, like other modifications in the
economy of living things, to the needs of the species. Or,
looking at it in another aspect, we may say that amid the
constant variations of animals and plants colour is ever tend-
ing to vary and to appear where it is absent ; and that natural
selection is constantly eliminating such tints as are injurious
to the species, or preserving and intensifying such as are
useful.

This view is in accordance with the well-known fact of
colours which rarely or never appear in the species in a
state of nature, continually occurring among domesticated
animals and cultivated plants ; showing us that the capacity
to develop colour is ever present, so that almost any required
tint can be produced which may, under changed conditions,
be useful, in however small a degree.

Let us now see how these principles will enable us to
understand and explain the varied phenomena of colour in
nature, taking them in the order of our functional classifica-
tion of colours.

Theory of Protective Colours

We have seen that obscure or protective tints in their
infinitely varied degrees are present in every part of the
animal kingdom ; whole families or genera being often thus
coloured. Now the various brown, earthy, ashy, and other
neutral tints are those which would be most readily produced,
because they are due to an irregular mixture of many kinds

v COLOURS OF ANIMALS 361

of rays ; while pure tints require either rays of one kind only,
or definite mixtures in proper proportions of two or more
kinds of rays. This is well exemplified by the comparative
difficulty of producing definite pure tints by the mixture of
two or more pigments ; while a haphazard mixture of a
number of these will be almost sure to produce browns, olives,
or other neutral or dingy colours. An indefinite or irregular
absorption of some rays and reflection of others would, there-
fore, produce obscure tints ; while pure and vivid colours
would require a perfectly definite absorption of one portion
of the coloured rays, leaving the remainder to produce the
true complementary colour. This being the case, we may
expect these brown tints to occur when the need of protection
is very slight or even when it does not exist at all ; always
supposing that bright colours are not in any way useful to
the species. But whenever a pure colour is protective, — as
green in tropical forests, or white among arctic snows, — there
is no difficulty in producing it, by natural selection acting on
the innumerable slight variations of tint which are ever occur-
ing. Such variations may, as we have seen, be produced in
a great variety of ways, either by chemical changes in the
secretions, or by molecular changes in surface structure ; and
may be brought about by change of food, by the physiological
action of light, or by the normal process of generative varia-
tion. Protective colours therefore, however curious and com-
plex they may be in certain cases, offer no real difficulties.

Theory of Warning Colours

These differ greatly from the last class, inasmuch as they
present us with a variety of brilliant hues, often of the
greatest purity, and combined in striking contrasts and
conspicuous patterns. Their use depends upon their bold-
ness and visibility, not on the presence of any one colour ;
hence we find among these groups some of the most ex-
quisitely-coloured objects in nature. Many of the uneatable
caterpillars are strikingly beautiful ; while the Danaidae,
Heliconidae, and protected groups of Papilionidae, comprise a
series of butterflies of the most brilliant and contrasted
colours. The bright colours of many of the sea -anemones
and sea -slugs will probably be found to be in this sense

362 TROPICAL NATURE

protective, serving as a warning of their uneatableness.1 On
our theory none of these colours offer any difficulty. Con-
spicuousness being useful, every variation tending to brighter
and purer colours was selected ; the result being the beautiful
variety and contrast we find.

Imitative Warning Colours — the Theory of Mimicry
We now come to those groups which gain protection solely
by being mistaken for some of these brilliantly coloured but
uneatable creatures, and here a difficulty really exists, and to
many minds is so great as to be insuperable. It will be well
therefore to endeavour to explain how the resemblance in
question may have been brought about.

The most difficult case, and the one which may be taken
as a type of the whole class, is that of the genus Leptalis (a
group of South American butterflies allied to our common
white and yellow kinds), many of the larger species of which
are still white or yelloAv, and which are all eatable by birds
and other insectivorous creatures. But there are also a
number of species of Leptalis, which are brilliantly red,
yellow, and black, and which, band for band and spot for
spot, resemble some one of the Danaidse or Heliconidae which
inhabit the same district and which are nauseous and uneat-
able. Now the usual difficulty is, that a slight approach to
one of these protected butterflies would be of no use, while a
greater sudden variation is not admissible on the theory of
gradual change by indefinite slight variations. This objection
depends almost wholly on the supposition that, when the first
steps towards mimicry occurred, the South American Danaidse
were what they are now ; while the ancestors of the Leptalides
were like the ordinary white or yellow Pieridse to which they
are allied. But the Danaioid butterflies of South America are
so immensely numerous and so greatly varied, not only in colour
but in structure, that we may be sure they are of vast antiquity
and have undergone great modification. A large number of
them, however, are still of comparatively plain colours, often
rendered extremely elegant by the delicate transparency of
the wing membrane, but otherwise not at all conspicuous.

1 This has since been found to be the case by Professor Herdman (Trans.
Biol. Soc. Liverpool, vol. iv. p. 150).

v COLOURS OF ANIMALS 368

Many have only dusky or purplish bands or spots; others
have patches of reddish or yellowish brown — perhaps the
commonest colour among butterflies ; while a considerable
number are tinged or spotted with yellow, also a very common
colour, and one especially characteristic of the Pieridas, the
family to which Leptalis belongs. We may therefore reason-
ably suppose that in the early stages of the development of
the Danaidse, when they first began to acquire those nauseous
secretions which are now their protection, their colours were
somewhat plain ; either dusky with paler bands and spots, or
yellowish with dark borders, and sometimes with reddish
bands or spots. At this time they had probably shorter
wings and a more rapid flight, just like the other unprotected
families of butterflies. But, so soon as they became decidedly
unpalatable to any of their enemies, it would be an advantage
to them to be readily distinguished from all the eatable kinds ;
and as butterflies were no doubt already very varied in colour,
while all probably had wings adapted for rather quick or
jerking flight, the best distinction might have been found in
outline and habits ; whence would arise the preservation of
those varieties whose longer wings, bodies, and antennae, as
well as their slower flight, rendered them noticeable —
characters which now distinguish the whole group in every
part of the world.

Now it would be at this stage that some of the weaker-
flying Pieridse which happened to resemble some of the
Danaidse around them in their yellow and dusky tints and in
the general outline of their wings, would be sometimes mis-
taken for them by the common enemy, and would thus gain
an advantage in the struggle for existence. Admitting this
one step to be made, and all the rest must inevitably follow
from simple variation and survival of the fittest. So soon as
the nauseous butterfly varied in form or colour to such an
extent that the corresponding eatable butterfly no longer
closely resembled it, the latter would be exposed to attacks,
and only those variations would be preserved which kept up
the resemblance. At the same time we may well suppose the
enemies to become more acute and able to detect smaller
differences than at first. This would lead to the destruction
of all adverse variations, and thus keep up in continually

TROPICAL NATUEE

increasing complexity the outward mimicry which now so
amazes us. During the long ages in which this process has
been going on, and the Danaidae have been acquiring those
specialities of colour which aid in their preservation, many a
Leptalis may have become extinct from not varying suffi-
ciently in the right direction and at the right time to keep
up a protective resemblance to its neighbour ; and this well
accords with the comparatively small number of cases of true
mimicry, as compared with the frequency of those protective
resemblances to vegetable or inorganic objects whose forms
are less definite and colours less changeable. About a dozen
other genera of butterflies and moths mimic the Danaidse in
various parts of the world, and exactly the same explanation
will apply to all of them. They represent those species of
each group which, at the time when the Danaidse first
acquired their protective secretions, happened outwardly to
resemble some of them, and which have, by concurrent varia-
tion aided by a rigid selection, been able to keep up that
resemblance to the present day. l

Theory of Sexual Colours

In Mr. Darwin's celebrated work, The Descent of Man and
Selection in Relation to Sex, he has treated of sexual colour in
combination with other sexual characters, and has arrived at
the conclusion that all or almost all the colours of the higher
animals (including among these insects and all vertebrates)
are due to voluntary or conscious sexual selection ; and that
diversity of colour in the sexes is due, primarily, to the trans-
mission of colour-variations either to one sex only or to both
sexes, the difference depending on some unknown law, and
not being due to natural selection.

I have long held this portion of Mr. Darwin's theory to be
erroneous, and have argued that the primary cause of sexual
diversity of colour was the need of protection, repressing in

1 For fuller information on this subject the reader should consult Mr.
Bates' original paper, "Contributions to an Insect -fauna of the Amazon
Valley," in Transactions of the Linnean Society, vol. xxiii. p. 495 ; Mr.
Trimen's paper in vol. xxvi. p. 497 ; the author's essay on "Mimicry," etc.,
already referred to ; and, in the absence of collections of butterflies, the plates
of Heliconidae and Leptalidse, in Hewitson's Exotic Butterflies ; and Felder's
Voyage of the " Novara," may be examined.

COLOURS OF ANIMALS

the female those bright colours which are normally produced
in both sexes by general laws ; and I have attempted to
explain many of the more difficult cases on this principle
("A Theory of Birds' Nests," chap. vi. ante). As I have
since given much thought to this subject, and have arrived
at some views which appear to me to be of considerable im-
portance, it will be well to sketch briefly the theory I now hold,
and afterwards show its application to some of the detailed
cases adduced in Mr. Darwin's work.

The very frequent superiority of the male bird or insect
in brightness or intensity of colour, even when the general
coloration is the same in both sexes, now seems to me to be,
in great part, due to the greater vigour and activity and the
higher vitality of the male. The colours of an animal usually
fade during disease or weakness, while robust health and
vigour adds to their intensity. This is a most important and
suggestive fact, and one that appears to hold universally. In
all quadrupeds a " dull coat " is indicative of ill-health or low
condition, while a glossy coat and sparkling eye are the
invariable accompaniments of health and vital activity. The
same rule applies to the feathers of birds, whose colours are
only seen in their purity during perfect health ; and a similar
phenomenon occurs even among insects, for the bright hues
of caterpillars begin to fade as soon as they become inactive
preparatory to undergoing their transformation, or if attacked
by disease. Even in the vegetable kingdom we see tke same
thing, for the tints of foliage are deepest, and the colours of
flowers and fruits richest, on those plants which are in the
most healthy and vigorous condition.

This intensity of coloration becomes most developed in the
male during the breeding season, when the vitality is at a
maximum. It is also very general in those cases in which
the male is smaller than the female, as in the hawks and in
most butterflies and moths. The same phenomena occur,
though in a less marked degree, among mammalia. When-
ever there is a difference of colour between the sexes the
male is the darker or more strongly marked, and the differ-
ence of intensity is most visible during the breeding season
(Descent of Man, p. 533). Numerous cases among domestic
animals also prove that there is an inherent tendency in the

366 TROPICAL NATURE

male to special developments of dermal appendages and colour,
quite independently of sexual or any other form of selection.
Thus — " the hump on the male zebu cattle of India, the tail
of fat-tailed rams, the arched outline of the forehead in the
males of several breeds of sheep, and the mane, the long hairs
on the hind legs, and the dewlap of the male of the Berbura
goat " — are all adduced by Mr. Darwin as instances of char-
acters peculiar to the male, yet not derived from any parent
ancestral form. Among domestic pigeons the character of
the different breeds is often most strongly manifested in the
male birds ; the wattles of the carriers and the eye- wattles of
the barbs are largest in the males, and male pouters distend
their crops to a much greater extent than do the females,
while the cock fantails often have a greater number of tail-
feathers than the females. There are also some varieties of
pigeons of which the males are striped or spotted with black,
while the females are never so spotted (Animals and Plants
under Domestication, i. 161) ; yet in the parent stock of these
pigeons there are no differences between the sexes either of
plumage or colour, and artificial selection has not been applied
to produce them.

The greater intensity of coloration in the male, which may
be termed the normal sexual difference, would be further
developed by the combats of the males for the possession of
the females. The most vigorous and energetic usually being
able to» rear most offspring, intensity of colour, if dependent
on, or correlated with vigour, would tend to increase. But
as differences of colour depend upon minute chemical or
structural differences in the organism, increasing vigour acting
unequally on different portions of the integument, and often
producing at the same time abnormal developments of hair,
horns, scales, feathers, etc., would almost necessarily lead also
to variable distribution of colour, and thus to the production
of new tints and markings. These acquired colours would,
as Mr. Darwin has shown, be transmitted to both sexes or
to one only, according as they first appeared at an early age,
or in adults of one sex ; and thus we may account for some
of the most marked differences in this respect. With the
exception of butterflies, the sexes are almost alike in the
great majority of insects. The same is the case in mammals

v COLOUKS OF ANIMALS 367

and reptiles, while the chief departure from the rule occurs
in birds, though even here in very many cases the law of
sexual likeness prevails. But in all cases where the increas-
ing development of colour became disadvantageous to the
female, it would be checked by natural selection, and thus
produce those numerous instances of protective colouring in
the female only, which occur most frequently in these two
groups, birds and butterflies.

Colour as a means of Recognition

There is also, I believe, a very important purpose and use
of the varied colours of the higher animals in the facility it
affords for recognition by the sexes or by the young of the
same species; and it is this use which probably fixes and
determines the coloration in many cases. When differences
in the size and form of allied species are very slight, colour
affords the only means of recognition at a distance, or while
in motion ; and such a distinctive character must therefore
be of especial value to flying insects which are continually in
motion, and encounter each other, as it were, by accident.
This view offers us an explanation of the curious fact that
among butterflies the females of closely-allied species in the
same locality sometimes differ considerably, while the males
are much alike ; for, as the males are the swiftest and by far
the highest fliers, and seek out the females, it would evidently
be advantageous for them to be able to recognise their true
partners at some distance off. This peculiarity occurs with
many species of Papilio, Diadema, Adolias, and Colias; and
these are all genera, the males of which are strong on the
wing and mount high in the air. In birds such marked
differences of colour are not required owing to their higher
organisation and more perfect senses, which render recogni-
tion easy by means of a combination of very slight differential
characters. 1

This principle may perhaps, however, account for some
anomalies of coloration among the higher animals. Thus,
while admitting that the hare and the rabbit are coloured
protectively, Mr. Darwin remarks that the latter, while

1 For numerous examples of recognition-colours in birds, see Darwinism,
pp. 217-226.

TROPICAL NATURE

running to its burrow, is made conspicuous to the sportsman,
and no doubt to all beasts of prey, by its upturned white tail.
But this very conspicuousness while running away, may be
useful as a signal and guide to the young, who are thus
enabled to escape danger by following the older rabbits,
directly and without hesitation, to the safety of the burrow ;
and this may be the more important from the semi-nocturnal
habits of the animal. If this explanation is correct, and it
certainly seems probable, it may serve as a warning of how
impossible it is, without exact knowledge of the habits of an
animal and a full consideration of all the circumstances, to
decide that any particular coloration cannot be protective or
in any way useful. Mr. Darwin himself is not free from such
assumptions. Thus, he says : — " The zebra is conspicuously
striped, and stripes cannot afford any protection on the open
plains of South Africa." But the zebra is a very swift
animal, and, when in herds, by no means void of means of
defence. The stripes therefore may be of use by enabling
stragglers to distinguish their fellows at a distance, and they
may be even protective when the animal is at rest among
herbage — the only time when it would need protective colour-
ing. Until the habits of the zebra have been observed with
special reference to these points, it is surely somewhat hasty
to declare that the stripes "cannot afford any protection."1

Colowr proportionate to Integumentary Development
The wonderful display and endless variety of colour in
which butterflies and birds so far exceed all other animals,
seems primarily due to the excessive development and endless
variations of the integumentary structures of these two
groups. No insects have such widely expanded wings in pro-
portion to their bodies as butterflies and moths ; in none do
the wings vary so much in size and form, and in none are they
clothed with such a beautiful and highly-organised coating of
scales. According to the general principles of the production
of colour already explained, these long continued expansions of
membranes and developments of surface-structures must have
led to numerous colour-changes, which have been sometimes
checked, sometimes fixed and utilised, sometimes intensified,
1 For further information on this point, see Darwinism, p. 220,

v COLOURS OF ANIMALS 369

by natural selection, according to the needs of the animal.
In birds, too, we have the wonderful clothing of plumage —
the most highly organised, the most varied, and the most
expanded of all dermal appendages. The endless processes of
growth and change during the development of feathers, and
the enormous extent of this delicately-organised surface, must
have been highly favourable to the production of varied
colour-effects, which, when not injurious, have been merely
fixed for purposes of specific identification, but have often
been modified or suppressed whenever different tints were
needed for purposes of protection.

Selection by Females not a cause of Colour
To conscious sexual selection — that is, the actual choice by
the females of the more brilliantly -coloured males or the
rejection of those less gaily coloured — I believe very little if
any effect is directly due. It is undoubtedly proved that in
birds the females do sometimes exert a choice; but the
evidence of this fact, collected by Mr. Darwin (Descent of Man,
chap, xiv.), does not prove that colour determines that choice,
while much of the strongest evidence is directly opposed to
this view. All the facts appear to be consistent with the
choice depending on a variety of male characteristics, with
some of which colour is often correlated. Thus it is the
opinion of some of the best observers that vigour and liveli-
ness are most attractive, and these are no doubt usually
associated with intensity of colour. Again, the display of the
various ornamental appendages of the male during courtship
may be attractive ; but these appendages, with their bright
colours or shaded patterns, are due probably to general laws
of growth, and to that superabundant vitality which we have
seen to be a cause of colour. But there are many considera-
tions which seem to show that the possession of these orna-
mental appendages and bright colours in the male is not an
important character functionally, and that it has not been
produced by the action of conscious sexual selection. Amid
the copious mass of facts and opinions collected by Mr.
Darwin as to the display of colour and ornaments by the male
birds, there is a total absence of any evidence that the females,
as a rule, admire or even notice this display. The hen, the
2B

370 TROPICAL NATURE

turkey, and the pea-fowl go on feeding while the male is dis-
playing his finery ; and there is reason to believe that it is
his persistency and energy rather than his beauty which
wins the day. Again, evidence collected by Mr. Darwin
himself, proves that each bird finds a mate under any
circumstances. He gives a number of cases of one of a
pair of birds being shot, and the survivor being always
found paired again almost immediately. This is sufficiently
explained on the assumption that the destruction of birds by
various causes is continually leaving widows and widowers in
nearly equal proportions, and thus each one finds a fresh
mate; and it leads to the conclusion that permanently
unpaired birds are very scarce, so that, speaking broadly,
every bird finds a mate and breeds. But this would almost
or quite neutralise any effect of sexual selection of colour or
ornament, since the less highly-coloured birds would be at
little or no disadvantage as regards leaving healthy offspring.
If, however, heightened colour is correlated with health and
vigour ; and if these healthy and vigorous birds provide best
for their young, and leave offspring which, being equally
healthy and vigorous, can best provide for themselves — which
cannot be denied — then natural selection becomes a preserver
and intensifier of colour.

Another most important consideration is, that male butter-
flies rival or even excel the most gorgeous male birds in
bright colours and elegant patterns ; and among these there is
literally not one particle of evidence that the female is influ-
enced by colour, or even that she has any power of choice,
while there is much direct evidence to the contrary (Descent
of Man, p. 318). The weakness of the evidence for conscious
sexual selection among these insects is so palpable that Mr.
Darwin is obliged to supplement it by the singularly incon-
clusive argument that, " Unless the female prefer one male to
another, the pairing must be left to mere chance, and this
does not appear probable" (Ic. p. 317). But he has just
said : " The males sometimes fight together in rivalry, and
many may be seen pursuing or crowding round the same
female;" while in the case of the silk-moths, "the females
appear not to evince the least choice in regard to their part-
ners." Surely the plain inference from all this is, that males

v COLOURS OF ANIMALS 371

fight and struggle for the almost passive female, and that the
most vigorous and energetic, the strongestxwlnged or the most
persevering, wins her. How can there be chance in this ?
Natural selection would here act, as in birds, in perpetuating
the strongest and most vigorous males ; and as these would
usually be the more highly coloured of their race, the same
results would be produced as regards the intensification and
variation of colour in the one case as in the other.

Let us now see how these principles will apply to some of
the cases adduced by Mr. Darwin in support of his theory of
conscious sexual selection.

In Descent of Man, 2d ed., pp. 307-316, we find an elaborate
account of the various modes of colouring of butterflies and
moths, proving that the coloured parts are always more or
less displayed, and that they have some evident relation to
an observer. Mr. Darwin then says : " From the several
foregoing facts it is impossible to admit that the brilliant
colours of butterflies, and of some few moths, have commonly
been acquired for the sake of protection. We have seen that
their colours and elegant patterns are arranged and exhibited
as if for display. Hence I am led to believe that the females
prefer or are most excited by the more brilliant males ; for on
any other supposition the males would, as far as we can see,
be ornamented to no purpose" (I.e. p. 316). I am not aware
that any one has ever maintained that the brilliant colours of
butterflies have " commonly been acquired for the sake of
protection," yet Mr. Darwin has himself referred to cases in
which the brilliant colour is so placed as to serve for protec-
tion; as, for example, the eye- spots on the hind wings of
moths, which are pierced by birds and so save the vital parts
of the insect, while the bright patch on the orange-tip butter-
flies, which Mr. Darwin denies are protective, may serve the
same purpose. It is, in fact, somewhat remarkable how very
generally the black spots, ocelli, or bright patches of colour
are on the tips, margins, or discs of the wings ; and as the
insects are necessarily visible while flying, and this is the
time when they are most subject to attacks by insectivorous
birds, the position of the more conspicuous parts at some
distance from the body may be a real protection to them.
Again, Mr. Darwin admits that the white colour of the male

372 TROPICAL NATURE

ghost-moth may render it more easily seen by the female
while flying about in the dusk ; and if to this we add that it
will be also more readily distinguished from allied species, we
have a reason for diverse ornamentation in these insects quite
sufficient to account for most of the facts, without believing
in the selection of brilliant males by the females, for which
there is not a particle of evidence.1

Probable use of the Horns of Beetles

A somewhat analogous case is furnished by the immense
horns of some beetles of the families Copridae and Dynastidse,
which Mr. Darwin admits are not used for fighting, and there-
fore concludes are ornaments, developed through selection of
the larger -horned males by the females. But it has been
overlooked that these horns may be protective. The males
probably fly about most, as is usually the case with male
insects ; and as they generally fly at dusk they are subject to
the attacks of large-mouthed goatsuckers and podargi, as well
as of insect -eating owls. Now the long, pointed, or forked
horns, often divergent, or movable with the head, would
render it very difficult for these birds to swallow such insects,
and would therefore be an efficient protection, just as are the
hooked spines of some stingless ants and the excessively hard
integuments of many beetles, against the smaller insectivorous
birds.

Cause of the greater Brilliancy of some Female Insects
The facts given by Mr. Darwin to show that butterflies
and other insects can distinguish colours and are attracted by
colours similar to their own, are quite consistent with the
view that colour, which continually tends to appear, is utilised
for purposes of identification and distinction when not required
to be modified or suppressed for the purpose of protection.
The cases of the females of some species of Thecla, Callidryas,
Colias, and Hipparchia, which have more conspicuous mark-
ings than the male, may be due to several causes : to obtain
greater distinction from other species ; for protection from
birds, as in the case of the yellow-underwing moths; while
sometimes — as in Hipparchia — the lower intensity of colour-
1 See M. Fabre's testimony on this point, Descent of Man, p. 291.

v COLOURS OF ANIMALS 373

ing in the female may lead to more contrasted markings.
Mr. Darwin thinks that here the males have selected
the more beautiful females ; although one chief fact in
support of his theory of conscious sexual selection is, that
throughout the whole animal kingdom the males are usually
so ardent that they will accept any female, while the females
are coy and choose the handsomest males, whence it is
believed the general brilliancy of males as compared with
females has arisen.

Perhaps the most curious cases of sexual difference of
colour are those in which the female is very much more gaily
coloured than the male. This occurs most strikingly in some
species of Pieris in South America, and of Diadema in the
Malay islands ; and in both cases the females resemble species
of the uneatable Danaidse and Heliconidse, and thus gain a
protection. In the case of Pieris pyrrha, P. malenka, and P.
lorena, the males are plain white and black, while the females
are orange, yellow, and black, and so banded and spotted as
exactly to resemble species of Heliconidae. Mr. Darwin
admits that these bright colours have been acquired for
protection ; but as there is no apparent cause for the strict
limitation of the colour to the female, he believes that it has
been kept down in the male by its being unattractive to her.
This appears to me to be a supposition opposed to the whole
theory of sexual selection itself. For this theory is, that
minute variations of colour in the male are attractive to the
female, have always been selected, and that thus the brilliant
male colours have been produced. But in this case he thinks
that the female butterfly had a constant aversion to every
trace of colour, even when we must suppose it was constantly
recurring during the successive variations which resulted in
such a marvellous change in herself. But the case admits of
a much more simple interpretation. For if we consider the
fact that the females frequent the forests where the Heli-
conidse abound, while the males fly much in the open and
assemble in great numbers with other white and yellow
butterflies on the banks of rivers, may it not be possible
that the appearance of orange stripes or patches would be as
injurious to the male as it is useful to the female, by making
him a more easy mark for insectivorous birds among his

374 TROPICAL NATURE

white companions ? This seems a more probable supposition
than the altogether hypothetical choice of the female, some-
times exercised in favour of and sometimes against every new
variety of colour in her partner.

A strictly analogous case is that of the glow-worm, whose
light, as originally suggested by Mr. Belt, is admitted to
be a warning of its uneatability to insectivorous nocturnal
animals. The male, having wings, does not require this
protection. In the tropics the number of nocturnal insect-
ivorous birds and bats is very much greater, hence winged
species possess the light, as they would otherwise be eaten by
mistake for more savoury insects; and it may be that the
luminous Elateridse of the tropics really mimic the true fire-
flies (Lampyridse), which are uneatable. This is the more
probable, as the Elateridae, in the great majority of species,
have brown or protective colours, and are therefore certainly
palatable to insectivorous animals.

Origin of the Ornamental Plumage of Male Birds

We now come to such wonderful developments of plum-
age and colour as are exhibited by the peacock and the
Argus-pheasant; and I may here mention that it was the case
of the latter bird, as fully discussed by Mr. Darwin, which
first shook my belief in " sexual," or more properly " female "
selection. The long series of gradations by which the beauti-
fully shaded ocelli on the secondary wing-feathers of this bird
have been produced, are clearly traced out, the result being a
set of markings so exquisitely shaded as to represent " balls
lying loose within sockets " — purely artificial objects of which
these birds could have no possible experience. That this
result should have been attained, through thousands and tens
of thousands of female birds all preferring those males whose
markings varied slightly in this one direction, this uniformity
of choice continuing through thousands and tens of thousands
of generations, is to me absolutely incredible. And when,
further, we remember that those which did not so vary
'would also, according to all the evidence, find mates and leave
offspring, the actual result seems quite impossible of attain-
ment by such means.

v .« COLOURS OF ANIMALS 375

Without pretending to solve completely so difficult a
problem as that of the origin and uses of the variously
coloured plumes and ornaments so often possessed by male
birds, I would point out a few facts which seem to afford a
clue. And first, the most highly-coloured and most richly-
varied markings occur on those parts of the plumage which
have undergone the greatest modification, or have acquired
the most abnormal development. In the peacock, the tail-
coverts are enormously developed, and the "eyes" are
situated on the greatly dilated ends of these elongated
feathers. In the birds-of-paradise, breast, or neck, or head,
or tail-feathers, are greatly developed and highly coloured.
The hackles of the cock and the scaly breasts of humming-
birds are similar developments ; while in the Argus-pheasant
the secondary quills are so enormously lengthened and
broadened as to have become almost useless for flight. Now
it is easily conceivable that during this process of develop-
ment inequalities in the distribution of colour may have
arisen in different parts of the same feather, and that spots
and bands may thus have become broadened out into shaded
spots or ocelli, in the way indicated by Mr. Darwin, much
as the spots and rings on a soap-bubble increase with increas-
ing tenuity. This is the more probable, because in domestic
fowls varieties of colour tend to become symmetrical, quite
independently of sexual selection (Descent of Man, p. 424).
This is one of those crucial facts which, on Mr. Darwin's
theory, ought not to happen, and which plainly indicate that
symmetrical markings arise from the action of some general
laws of colour-development.

If now we accept the evidence of Mr. Darwin's most
trustworthy correspondents, that the choice of the female, so
far as she exerts any, falls upon the " most vigorous, defiant,
and mettlesome male;" and if we further believe, what is
certainly the case, that these are as a rule the most brightly
coloured and adorned with the finest developments of plum-
age— we have a real and not a hypothetical cause at work.
For these most healthy, vigorous, and beautiful males will
have the choice of the finest and most healthy females, will
have the most numerous and healthy families, and will be
able best to protect and rear those families. Natural selec-

376 TROPICAL NATURE

tion, and what may be termed male selection, will tend to
give them the advantage in the struggle for existence, and
thus the fullest plumage and the finest colours will be trans-
mitted, and tend to advance in each succeeding generation.

Theory of Display of Ornaments by Males

The full and interesting account given by Mr. Darwin of
the colours and habits of male and female birds (Descent of
Man, chaps, xiii. and xiv.), proves that in most, if not in
all cases, the male birds fully display their ornamental plum-
age before the females or in rivalry with each other ; but on
the essential point of whether the female's choice is deter-
mined by minute differences in these ornaments or in their
colours, there appears to be an entire absence of evidence.
In the section on " Preference for particular Males by the
Females," the facts quoted show indifference to colour, except
that some colour similar to their own seems to be preferred.
But in the case of the hen canary who chose a greenfinch in
preference to either chaffinch or goldfinch, gay colours had
evidently no preponderating attraction. There is some evi-
dence adduced that female birds may, and probably do,
choose their mates, but none whatever that the choice is
determined by difference of colour ; and no less than three
eminent breeders informed Mr. Darwin that they " did not
believe that the females prefer certain males on account of
the beauty of their plumage." Again, Mr. Darwin himself
says : " As a general rule colour appears to have little influ-
ence on the pairing of pigeons." The oft-quoted case of Sir
R. Heron's pea-hens, which preferred an '"old pied cock" to
those normally coloured, is a very unfortunate one, because
pied birds are just those that are not favoured in a state of
nature, or the breeds of wild animals would become as varied
and mottled as our domestic varieties. If such irregular
fancies were not rare exceptions, the production of definite
colours and patterns by the choice of the female birds, or in
any other way, would be impossible.

There remains, however, to be accounted for, the remark-
able fact of the display by the male of each species of its
peculiar beauties of plumage and colour — a display which Mr.

v COLOURS OF ANIMALS 377

Darwin evidently considers to be the strongest argument in
favour of conscious selection by the female. This display is,
no doubt, a very interesting and important phenomenon ; but
it may, I believe, be satisfactorily explained on the general
principles here laid down, without calling to our aid a purely
hypothetical choice exerted by the female bird.

At pairing-time the male is in a state of excitement, and
full of exuberant energy. Even unornamental birds flutter
their wings or spread them out, erect their tails or crests,
and thus give vent to the nervous excitability with which
they are overcharged. It is not improbable that crests and
other erectile feathers may be primarily of use in frightening
away enemies, since they are generally erected when angry
or during combat. Those individuals who were most pug-
nacious and defiant, and who brought these erectile plumes
most frequently and most powerfully into action, would
tend to leave them further developed in some of their
descendants. If, in the course of this development, colour
appeared — and we have already shown that such develop-
ments of plumage are a very probable cause of colour —
we have every reason to believe it would be most vivid in
these most pugnacious and energetic individuals; and as
these would always have the advantage in the rivalry
for mates (to which advantage the excess of colour and
plumage might sometimes conduce), there seems nothing to
prevent a progressive development of these ornaments in all
dominant races ; that is, wherever there was such a surplus of
vitality, and such complete adaptation to conditions, that the
inconvenience or danger produced by such ornaments was so
comparatively small as not to affect the superiority of the
race over its nearest allies.

But if those portions of the plumage which were originally
erected under the influence of anger or fear became largely
developed and brightly coloured, the actual display under
the influence of jealousy or sexual excitement becomes quite
intelligible. The males, in their rivalry with each other,
would endeavour to excel their enemies as far as voluntary
exertion would enable them to do so, just as they endeavour
to rival each other in song, even sometimes to the point of
causing their own destruction.

378 TROPICAL NATURE

Natural Selection as neutralising Sexual Selection
There is also a general argument against Mr. Darwin's
views on this question, founded on the nature and potency
of " natural " as opposed to " sexual " selection, which appears
to me to be of itself almost conclusive as to the whole matter
at issue. Natural selection, or the survival of the fittest,
acts perpetually and on an enormous scale. Taking the off-
spring of each pair of birds as, on the average, only six
annually, one-third of these at most will be preserved, while
the two-thirds which are least fitted will die. At intervals of
a few years, whenever unfavourable conditions occur, five-
sixths, nine-tenths, or even a greater proportion of the whole
yearly production are weeded out, leaving only the most
perfect and best adapted to survive. Now unless these sur-
vivors are, on the whole, the most ornamental, this rigid
natural selection must neutralise and destroy any influence
that may be exerted by female selection. The utmost that
can be claimed for the latter is, that a small fraction of the
least ornamented do not obtain mates, while a few of the
most ornamented may leave more than the average number of
offspring. Unless, therefore, there is the strictest correlation
between ornament and general perfection, the more brightly
coloured or ornamented varieties can obtain no permanent
advantage ; and if there is (as I maintain) such a correlation,
then the sexual selection of colour or ornament, for which
there is little or no evidence, becomes needless, because
natural selection, which is an admitted vera causa, will itself
produce all the results.

In the case of butterflies the argument becomes even
stronger, because the fertility is so much greater than in
birds, and the weeding-out of the unfit takes place, to a great
extent, in the egg and larva state. Unless the eggs and
larvae which escaped to produce the next generation were
those which would produce the more highly-coloured butter-
flies, it is difficult to perceive how the slight preponderance
of colour sometimes selected by the females should not be
wholly neutralised by the extremely rigid selection for other
qualities to which the offspring in every stage are exposed.
The only way in which we can account for the observed facts

v COLOURS OF ANIMALS 879

is, by the supposition that colour and ornament are strictly
correlated with health, vigour, and general fitness to survive.
We have shown that there is reason to believe that this is
the case, and if so, conscious sexual selection becomes as
unnecessary as it would certainly be ineffective.

Greater Brilliancy of some Female Birds
There is one other very curious case of sexual colouring
among birds — that, namely, in which the female is decidedly
brighter or more strongly marked than the male, as in the
fighting quails (Turnix), painted snipe (Ehynchsea), two
species of phalarope (Phalaropus), and the common cassowary
(Casuarius galeatus). In all these cases it is known that the
males take charge of and incubate the eggs, while the females
are almost always larger and more pugnacious.

In my "Theory of Birds' Nests" (see p. 132) I imputed
this difference of colour to the greater need for protection by
the male bird while incubating, to which Mr. Darwin has
objected that the difference is not sufficient, and is not always
so distributed as to be most effective for this purpose ; and he
believes that it is due to reversed sexual selection — that is, to
the female taking the usual rdle of the male, and being chosen
for her brighter tints. We have already seen reason for
rejecting this latter theory in every case ; and I also admit
that Mr. Darwin's criticism is sound, and 'that my theory of
protection is, in this case, only partially, if at all, applicable.
But the theory now advanced, of intensity of colour being
due to general vital energy, is quite applicable ; and the fact
that the superiority of the female in this respect is quite
exceptional, and is therefore probably not in any case of very
ancient date, will account for the difference of colour thus
produced being always very slight.

Colour-development as illustrated by Humming-birds
Of the mode of action of the general principles of colour-
development among animals, we have an excellent example in
the humming-birds. Of all birds these are at once the
smallest, the most active, and the fullest of vital energy.
When poised in the air their wings are invisible owing to
the rapidity of their motion, and when startled they dart

TROPICAL NATURE

away with the rapidity of a flash of light. Such active
creatures would not be an easy prey to any rapacious bird ;
and if one at length was captured, the morsel obtained would
hardly repay the labour. We may be sure, therefore, that
they are practically unmolested. The immense variety they
exhibit in structure, plumage, and colour, indicates a high
antiquity for the race; while their general abundance in
individuals shows that they are a dominant group, well
adapted to all the conditions of their existence. Here we
find everything necessary for the development of accessory
plumes and colour. The surplus vital energy shown in their
combats and excessive activity has expended itself in ever-
increasing developments of plumage, and greater and greater
intensity of colour, regulated only by the need for specific
identification which would be especially required in such
small and mobile creatures. Thus may be explained those
remarkable differences of colour between closely-allied species,
one having a crest like the topaz, while in another it resembles
the sapphire. The more vivid colours and more developed
plumage of the males, I am now inclined to think, may be
almost wholly due to their greater vital energy, and to those
general laws which lead to such superior developments even
in domestic breeds ; but in some cases the need of protection
by the female while incubating, to which I formerly imputed
the whole phenomenon, may have suppressed a portion of the
ornament which she would otherwise have attained.

The extreme pugnacity of humming-birds has been noticed
by all observers, and it seems to be to some extent propor-
tioned to the degree of colour and ornament in the species.
Thus Mr. Salvin observes of Eugenes fulgens, that it is " a most
pugnacious bird," and that " hardly any species shows itself
more brilliantly on the wing." Again of Campy lop terus
hemileucurus : " the pugnacity of this species is remarkable.
It is very seldom that two males meet without an aerial
battle ;" and "the large and showy tail of this humming-bird
makes it one of the most conspicuous on the wing." Again,
the elegant frill -necked Lophornis ornatus " is very pug-
nacious, erecting its crest, throwing out its whiskers, and
attacking every humming-bird that may pass within its range
of vision ; " and of another species, L. magnificus, it is said

COLOURS OF ANIMALS

that "it is so bold that the sight of man creates no alarm."
The beautifully-coloured Thaumastura cora "rarely permits
any other humming-bird to remain in its neighbourhood, but
wages a continual and terrible war upon them." The magni-
ficent bar-tail, Cometes sparganurus, one of the most imposing
of all the humming-birds, is extremely fierce and pugnacious,
" the males chasing each other through the air with surprising
perseverance and acrimony." These are all the species I find
noticed as being especially pugnacious, and every one of them
is exceptionally coloured or ornamented, while not one of
the small, plain, and less ornamental species are so described,
although many of them are common and well observed species.
It is also to be noticed that the remarkable pugnacity of these
birds is not confined to one season or even to birds of the
same species, as is usual in sexual combats, but extends to any
other species that may be encountered, while they are said
even to attack birds of prey that approach too closely to
their nests. It must be admitted that these facts agree well
with the theory that colour and ornament are due to surplus
vital energy and a long course of unchecked development.
We have also direct evidence that the males are more active
and energetic than the females. Mr. Gosse says that the
whirring made by the male Polytmus humming-bird is shriller
than that produced by the female ; and he also informs us
that the male flies higher and frequents mountains, while the
female keeps to the lowlands.1

Theory of Normal Colours

The remaining kinds of animal colours, those which can
neither be classed as protective, warning, nor sexual, are for
the most part readily explained on the general principles of
the development of colour which we have now laid down. It
is a most suggestive fact that in cases where colour is required
only as a warning, as among the uneatable caterpillars, we
find, not one or two glaring tints only, but every kind of
colour disposed in elegant patterns, and exhibiting almost as
much variety and beauty as among insects and birds. Yet

1 Some other cases are noticed at p. 317. For some further develop-
ments and illustrations of the theory of sexual colour, see Darwinism,
chap. x.

382 TROPICAL NATURE

here, not only is sexual selection out of the question, but
the need for recognition and identification by others of the
same species seems equally unnecessary. We can then only
impute this variety to the normal production of colour in
organic forms when fully exposed to light and air and under-
going great and rapid developmental modification. Among
more perfect animals, where the need for recognition has been
added, we find intensity and variety of colour at its highest
pitch among the South American butterflies of the families
Heliconidse and Danaidse, as well as among the Nymphalidse
and Erycinidse, many of which obtain the necessary protection
in other ways. Among birds also, wherever the habits are
such that no special protection is needed for the females, and
where the species frequent the depths of tropical forests, and
are thus naturally protected from the swoop of birds of prey,
we find almost equally intense coloration, as in the trogons,
barbets, and gapers.

Local Causes of Colour-development

Another real, though as yet inexplicable cause of diversity
of colour is to be found in the influence of locality. It is
observed that species of totally distinct groups are coloured
alike in one district, while in another district the allied
species all undergo the same change of colour. Cases of this
kind have been adduced by Mr. Bates, by Mr. Darwin, and
by myself, and I will here give the more curious and important
examples which I have been able to collect.1

The Influence of Locality on Colour in Butterflies and Birds
Our first example is from tropical Africa, where we find
two unrelated groups of butterflies belonging to two very
distinct families (Nymphalidse and Papilionidse) characterised by
a prevailing blue-green colour not found in any other continent.2
Again, we have a group of African Pieridse which are white
or pale yellow with a marginal row of bead-like black spots ;
and in the same country one of the Lycsenidae (Leptena

1 These were first given in my Address to the Biological Section of the
British Association at Glasgow in 1876.

2 Romaleosoma and Euryphene (Nymphalidae), Papilio zalmoxis and
several species of the Nireus-group (Papilionidae).

COLOURS OF ANIMALS

erastus) is coloured so exactly like these that it was at first
described as a species of Pieris. None of these four groups
are known to be in any way specially protected, so that the
resemblance cannot be due to protective mimicry.

In South America we have far more striking cases, for in
the three subfamilies Danainse, Acrseinse, and Heliconiinae, all
of which are specially protected, we find identical tints and
patterns reproduced, often in the greatest detail, each peculiar
type of coloration being characteristic of distinct geographical
subdivisions of the continent. Nine very distinct genera are
implicated in these parallel changes — Lycorea, Ceratinia,
Mechanitis, Ithomia, Melinsea, Tithorea, Acrsea, Heliconius,
and Eueides, groups of three or four (or even five) of them
appearing together in the same livery in one district, while
in an adjoining district most or all of them undergo a simul-
taneous change of coloration or of marking. Thus in the
genera Ithomia, Mechanitis, and Heliconius, we have species
with yellow apical spots in Guiana, all represented by allied
species with white apical spots in South Brazil. In Mechan-
itis, Melinaea, and Heliconius, and sometimes in Tithorea, the
species of the Southern Andes (Bolivia and Peru) are char-
acterised by an orange and black livery, while those of the
Northern Andes (New Granada) are almost always orange-
yellow and black. Other changes of a like nature, which it
would be tedious to enumerate, but which are very striking
when specimens are examined, occur in species of the same
groups inhabiting these same localities, as well as Central
America and the Antilles. The resemblance thus produced
between widely different insects is sometimes general, but
often so close and minute that only a critical examination of
structure can detect the difference between them. Yet all
are alike protected by the nauseous secretion which renders
them unpalatable to birds. 1

In another series of genera (Catagramma, Callithea, and
Agrias), all belonging to the Nymphalidae, we have the most
vivid blue ground, with broad bands of orange, crimson, or a
different tint of blue or purple, exactly reproduced in corre-
sponding, yet unrelated species, occurring in the same locality ;

1 The above cases have now been satisfactorily explained as a modified
form of mimicry. See Darwinism, pp. 249-257.

384 TROPICAL NATURE

yet, as none of these groups are known to be specially pro-
tected, this can hardly be true mimicry. A few species of
two other genera in the same country (Eunica and Siderone)
also reproduce the same colours, but with only a general
resemblance in the markings. Yet again, in tropical America
we have species of Apatura which, sometimes in both sexes,
sometimes in the female only, exactly imitate the peculiar
markings of another genus (Heterochroa) confined to America ;
here, again, neither genus is protected, and the similarity
must be due to unknown local causes.

But it is among islands that we find some of the most
striking examples of the influence of locality on colour,
generally in the direction of paler, but sometimes of darker
and more brilliant hues, and often accompanied by an unusual
increase of size. Thus in the Moluccas and New Guinea we
have several Papilios (P. euchenor, P. ormenus, and P. tydeus)
distinguished from their allies by a much paler colour, espe-
cially in the females, which are almost white. Many species
of Danais (forming the subgenus Ideopsis) are also very pale.
But the most curious are the Euploeas, which in the larger
islands are usually of rich dark colours, while in the small
islands of Banda, Ke, and Matabello at least three species not
nearly related to each other (E. hoppf eri, E. euripon, and E.
assimilata) are all broadly banded or suffused with white,
their allies in the larger islands being in each case very much
darker. Again, in the genus Diadema, belonging to a dis-
tinct family, three species from the small Aru and Ke islands
(D. deois, D. hewitsonii, and D. polymena) are all more
conspicuously white-marked than their representatives in the.
larger islands. In the beautiful genus Cethosia, a species
from the small island of Waigiou (C. cyrene) is the whitest of
the genus. Prothoe is represented by a blue species in the
continental island of Java, while those inhabiting the ancient
insular groups of the Moluccas and New Guinea are all pale
yellow or white. The genus Drusilla, almost confined to these
islands, comprises many species which are all very pale ;
while in the small island of Waigiou is found a very distinct
genus, Hyantis, which, though differing completely in the
neuration of the wings, has exactly the same pale colours and
large ocellated spots as Drusilla.

v COLOURS OF ANIMALS 385

Equally remarkable is the increase of size in some islands.
The small island of Amboina produces larger butterflies than
any of the much larger islands which surround it. This is
the case with at least a dozen butterflies belonging to many
distinct genera,1 so that it is impossible to attribute the fact
to other than some local influence. In Celebes, as I have
elsewhere pointed out,2 we have a peculiar form of wing and
much larger size running through a whole series of distinct
butterflies ; and this seems to take the place of any speciality
in colour.

In a very small collection of insects recently brought from
Duke-of-York island (situated between New Britain and New
Ireland) are several of remarkably white or pale coloration.
A species of Euplsea is the whitest of all known species of
that extensive genus ; while a beautiful diurnal moth is much
whiter than its ally in the larger island of New Guinea.
There is also a magnificent longicorn beetle almost entirely
of an ashy white colour.3

From the Fiji islands we have comparatively few butter-
flies ; but there are several species of Diadema of unusually
pale colours, some almost white.

The Philippine islands seem to have the peculiarity of
developing metallic colours. We find there at least three
species of Euplsea4 not closely related, and all of more
intense metallic lustre than their allies in other islands.
Here also we have one of the large yellow Ornithopterse
(0. magellanus), whose hind wings glow with an intense
opaline lustre not found in any other species of the entire
group; and an Adolias5 is larger and of more brilliant
metallic colouring than any other species in the archipelago.
In these islands also we find the extensive and wonderful
genus of weevils (Pachyrhynchus), which in their brilliant

1 Ornithoptera priamus, 0. Helena, Papilio deiphobus, P. ulysses, P. gam-
brisius, P. codrus, Iphias leucippe, Euplaea prothoe, Hestia idea, Athyma
jocaste, Diadema pandarus, Nymphalis pyrrhus, N. euryalus, Brasilia jairus.

3 Contributions to the Theory of Natural Selection, pp. 168-173.

3 These insects are described and figured in the Proceedings of the Zoolo-
gical Society for 1877, p. 139. Their names are Euplsea browni, Alcides
aurora, and Batocera browni.

4 Euplsea hewitsonii, E. diocletiana, E. Isetifica.
6 Adolias calliphorus.

2c

386 TROPICAL NATURE v

metallic colouring surpass anything found in the whole
eastern hemisphere, if not in the whole world.

In the Andaman islands, in the Bay of Bengal, there are a
considerable number of peculiar species of butterflies differing
slightly from those on the continent, and generally in the
direction of paler or more conspicuous colouring. Thus two
species of Papilio which on the continent have the tails black,
in their Andaman representatives have them either red or
white-tipped. l Another species 2 is richly blue-banded where
its allies are black ; while three species of distinct genera of
Nymphalidae 3 all differ from their allies on the continent in
being of excessively pale colours as well as of somewhat larger
size.

In Madagascar we have the very large and singularly
white -spotted Papilio antenor, while species of three other
genera4 are very white or conspicuous as compared with
their continental allies.

Passing to the West Indian islands and Central America
(which latter country has formed a group of islands in very
recent times), we have similar indications. One of the largest
of the Papilios inhabits Jamaica,5 while another, the largest
of its group, is found in Mexico.6 Cuba has two of the same
genus whose colours are of surpassing brilliancy ; 7 while the
fine genus Clothilda — confined to the Antilles and Central
America — is remarkable for its rich and showy colouring.

Persons who are not acquainted with the important
structural differences that distinguish these various genera
of butterflies can hardly realise the importance and the
significance of such facts as I have now detailed. It may
be well, therefore, to illustrate them by supposing parallel
cases to occur among the Mammalia. We might have, for
example, in Africa, the gnus, the elands, and the buffaloes,
all coloured and marked like zebras, stripe for stripe over
the whole body exactly corresponding. So the hares, mar-
mots, and squirrels of Europe might be all red with black
feet, while the corresponding species of Central Asia were all

1 Papilio rhodifer (near P. doubledayi), and Papilio charicles (near P.
memnon). 2 papiiio mayo.

3 Euplaea andamanensis, Cethosia biblis, Cyrestis codes.

4 Danais nossima, Melanitis massoura, Diadema dexithea.

6 Papilio homerus. • P. daunus. 7 P. gundlachiamis, P. villiersi.

v COLOURS OF ANIMALS 387

yellow with black heads. In North America we might have
raccoons, squirrels, and opossums, in parti-coloured livery of
white and black, so as exactly to resemble the skunk of the
same country ; while in South America they might be black
with a yellow throat -patch, so as to resemble with equal
closeness the tayra of the Brazilian forests. Were such
resemblances to occur in anything like the number and with
the wonderful accuracy of imitation met with among the
Lepidoptera, they would certainly attract universal attention
among naturalists, and would lead to the exhaustive study
of the influence of local causes in producing such startling
results.

One somewhat similar case does indeed occur among the
Mammalia, two singular African animals, the Aard-wolf (Pro-
teles) and the hyaena-dog (Lycaon), both strikingly resembling
hyenas in their general form as well as in their spotted
markings. Belonging as they all do to the Carnivora, though
to three distinct families, it seems quite an analogous case
to those we have imagined ; but as the Aard-wolf and the
hysena-dog are both weak animals compared with the hyaena,
the resemblance may be useful, and in that case would come
under the head of mimicry. This seems the more probable
because, as a rule, the colours of the Mammalia are protective,
and are too little varied to allow of the influence of local
causes producing any well-marked effects.

When we come to birds, however, the case is different,
for although they do not exhibit such distinct marks of the
influence of locality as do butterflies— probably because the
causes which determine colour are in their case more complex
— yet there are distinct indications of some effect of the kind,
and we must devote some little time to their consideration.

One of the most curious cases is that of the parrots of the
West Indian islands and Central America, several of which
have white heads or foreheads, occurring in two distinct
genera,1 while none of the more numerous parrots of South
America are so coloured. In the small island of Dominica
we have a very large and richly-coloured parrot (Chrysotis
augusta) corresponding to the large and richly -coloured
butterfly (Papilio homerus) of Jamaica.
1 Pionus albifrons and Chrysotis senilis (C. America), Chrysotis sallroi (Hayti).

388 TROPICAL NATURE

The Andaman islands are equally remarkable, at least six
of the peculiar birds differing from their continental allies in
being much lighter, and sometimes with a large quantity of
pure white in the plumage,1 exactly corresponding to what
occurs among the butterflies.

In the Philippines this is not so marked a feature ; yet we
have here the only known white-breasted kingcrow (Dicrurus
mirabilis) ; the newly discovered Eurylsemus steerii,- wholly
white beneath ; three species of Diceum, all white beneath ;
several species of Parus, largely white-spotted ; while many of
the pigeons have light ashy tints. The birds generally, how-
ever, have rich dark colours, similar to those which prevail
among the butterflies.

In Celebes we have a swallow-shrike and a peculiar small
crow allied to the jackdaw,2 whiter than any of their allies in
the surrounding islands, but otherwise the colours of the birds
call for no special remark.

In Timor and Flores we have white-headed pigeons,3 and
a long-tailed flycatcher almost entirely white.4

In Duke-of-York island, east of New Guinea, we find that
the four new species figured in the Proceedings of the Zoological
Society for 1877 are all remarkable for the unusual quantity
of white in their plumage. They consist of a flycatcher, a
diceum, a wood-swallow, and a ground-pigeon,5 all equalling
if- not surpassing their nearest allies in whiteness, although
some of these, from the Philippines, Moluccas, and Celebes,
are sufficiently remarkable in this respect.

In the small Lord Howe's island we have the recently
extinct white rail (Notornis alba), remarkably contrasting with
its allies in the larger islands of New Zealand.

We cannot, however, lay any stress on isolated examples
of white colour, since these occur in most of the great con-
tinents; but where we find a series of species of distinct
genera all differing from their continental allies in a whiter
coloration, as in the Andaman islands, Duke-of-York island,

1 Kittacincla albiventris, Geocichla albigularis, Sturnia andamanensis,
Hyloterpe grisola var., lanthaenas palumboides, Osmotreron chloroptera.

- Artamus monachus, Corvus advena.

3 Ptilopus cinctus, P. albocinctus. 4 Tchitrea affinis, var.

6 Monarcha vertically Diceum eximium, Artamus insignis, Phlogamas
jobannse.

COLOURS OF ANIMALS

and the West Indies, and, among butterflies, in the smaller
Moluccas, the Andamans, and Madagascar, we cannot avoid
the conclusion that in these insular localities some general
cause is at work.

There are other cases, however, in which local influences
seem to favour the production or preservation of intense
crimson or a very dark coloration. Thus in the Moluccas
and New Guinea alone we have bright red parrots belonging
to two distinct families,1 and which therefore most probably
have been independently produced or preserved by some
common cause. Here, too, and in Australia we have black
parrots and pigeons ; 2 and it is a most curious and suggestive
fact that in another insular sub-region — that of Madagascar
and the Mascarene islands — these same colours reappear in
the same two groups.3

Sense-perception influenced by Colour of the Integuments
Some very curious physiological facts bearing upon the
presence or absence of white colours in the higher animals
have lately been adduced by Dr. Ogle.4 It has been found
that a coloured or dark pigment in the olfactory region of
the nostrils is essential to perfect smell, and this pigment is
rarely deficient except when the whole animal is pure white.
In these cases the creature is almost without smell or taste.
This, Dr. Ogle believes, explains the curious case of the pigs
in Virginia adduced by Mr. Darwin, white pigs being killed
by a poisonous root which does not affect black pigs. Mr.
Darwin imputed this to a constitutional difference accompany-
ing the dark colour, which rendered what was poisonous to
the white-coloured animals quite innocuous to the black. Dr.
Ogle, however, observes that there is no proof that the black
pigs eat the root, and he believes the more probable explana-
tion to be that it is distasteful to them ; while the white pigs,
being deficient in smell and taste, eat it and are killed.
Analogous facts occur in several distinct families. White
sheep are killed in the Tarentino by eating Hypericum cris-

1 Lorius, Eos (Trichoglossidae), Eclectus (Palaeornithidae).
2 Microglossus, Calyptorhynchus, Turacsena.

8 Coracopsis, Alectraenas.
* Medico-Chirurgical Transactions, vol. liii. (1870).

390 TROPICAL NATURE

pum, while black sheep escape ; white rhinoceroses are said to
perish from eating Euphorbia candelabrum ; and white horses
are said to suffer from poisonous food where coloured ones
escape. Now it is very improbable that a constitutional
immunity from poisoning by so many distinct plants should,
in the case of such widely different animals, be always corre-
lated with the same difference of colour ; but the facts are
readily understood if the senses of smell and taste are
dependent on the presence of a pigment which is deficient
in wholly white animals. The explanation has, however,
been carried a step further, by experiments showing that the
absorption of odours by dead matter, such as clothing, is
greatly affected by colour, black being the most powerful
absorbent, then blue, red, yellow, and lastly white. We
have here a physical cause for the sense-inferiority of totally
white animals which may account for their rarity in nature,
for few, if any, wild animals are wholly white. The head,
the face, or at least the muzzle or the nose, are generally
black ; the ears and eyes are also often black ; and there is
reason to believe that dark pigment is essential to good
hearing, as it certainly is to perfect vision. We can there-
fore understand why white cats with blue eyes are so often
deaf, a peculiarity we notice more readily than their deficiency
of smell or taste.

If, then, the prevalence of white coloration is generally
associated with some deficiency in the acuteness of the most
important senses, this colour becomes doubly dangerous, for
it not only renders its possessor more conspicuous to its
enemies, but at the same time makes it less ready in detect-
ing the presence of danger. Hence, perhaps, the reason why
white appears more frequently in islands, where compe-
tition is less severe and enemies less numerous and varied.
Hence, also, a reason why cdbinoism, although freely occur-
ring in captivity, never maintains itself in a wild state,
while melanism does. The peculiarity of some islands
in having all their inhabitants of dusky colours (as the
Galapagos) may also perhaps be explained on the same
principles, for poisonous 'fruits may there abound which
weed out all white or light -coloured varieties owing to
their deficiency of smell and taste. We can hardly believe,

v COLOURS OF ANIMALS 391

however, that this would apply to white-coloured butterflies ;
and this may be a reason why the effect of an insular habitat
is more marked in these insects than in birds or mammals.1

It is even possible that this relation of sense -acuteness
with colour may have had some influence on the development
of the higher human races. If light tints of the skin were
generally accompanied by some deficiency in the senses of
smell, hearing, and vision, the white could never compete
with the darker races so long as man was in a very low or
savage condition, and wholly dependent for existence on the
acuteness of his senses. But as the mental faculties became
more fully developed and more important to his welfare than
mere sense-acuteness, the lighter tints of skin and hair and
eyes would cease to be disadvantageous whenever they were
accompanied by superior brain-power. Such variations would
then be preserved ; and thus may have arisen the Xantho-
chroic race of mankind, in which we find a high development
of intellect accompanied by a slight deficiency in the acuteness
of the senses as compared with the darker forms.

Summary on Colour-development in Animals
Let us now sum up the conclusions at which we have
arrived as to the various modes in which colour is produced
or modified in the animal kingdom.

The various causes of colour in the animal world are,
molecular and chemical change of the substance of their
integuments, or the action on it of heat, light, or moisture.
It is also produced by interference of light in superposed
transparent lamellae, or by excessively fine surf ace -striae.
These elementary conditions for the production of colour are
found everywhere in the surface-structures of animals, so that
its presence must be looked upon as normal, its absence as
exceptional.

Colours are fixed or modified in animals by natural
selection for various purposes; obscure or imitative colours
for concealment ; gaudy colours as a warning j and special
markings, either for easy recognition by strayed individuals,
females, or young, or to divert attack from a vital part, as in

1 In Darwinism, pp. 229, 230, 1 have suggested an explanation of most of
the facts of colour in islands as due to the lesser need of protection.

TROPICAL NATURE

the large brilliantly -marked wings of some butterflies and
moths.

Colours are produced or intensified by processes of develop-
ment, either where the integument or its appendages undergo
great extension or modification, or where there is a surplus of
vital energy, as in male animals generally, and more especially
at the breeding season.

Colours are also more or less influenced by a variety of
causes, such as the nature of the food, the photographic or
physiological action of light, and also by some unknown local
action, probably dependent on chemical peculiarities in the soil
or vegetation.

These various causes have acted and reacted in a variety
of ways, and have been modified by conditions dependent on
age or on sex, on competition with new forms, or on geo-
graphical or climatic changes. In so complex a subject, for
which experiment and systematic inquiry have done so little,
we cannot expect to explain every individual case, or solve
every difficulty ; but it is believed that all the great features of
animal coloration and many of the details become explicable
on the principles we have endeavoured to lay down.

It will perhaps be considered presumptuous to put forth
this sketch of the subject of colour in animals as a substitute
for one of Mr. Darwin's most highly elaborated theories —
that of voluntary or perceptive sexual selection ; yet I ven-
ture to think that it is more in accordance with the whole of
the facts, and with the theory of natural selection itself ; and
I would ask such of my readers as may be sufficiently in-
terested in the subject, to read again chapters xi. to xvi. of
the Descent of Man, and consider the whole subject from the
point of view here laid down. The explanation of almost all
the ornaments and colours of birds and insects as having been
produced by the perceptions and choice of the females, has,
I believe, staggered many evolutionists, but has been pro-
visionally accepted because it was the only theory that even
attempted to explain the facts. It may perhaps be a relief
to some of them, as it has been to myself, to find that the
phenomena can be conceived as dependent on the general
laws of development, and on the action of " natural selection,"
which theory will, I venture to think, be relieved from an

v COLOURS OF ANIMALS 393

abnormal excrescence and ga'in additional vitality by the
adoption of the views here imperfectly set forth.1

Although we have arrived at the conclusion that tropical
light and heat can in no sense be considered as the cause of
colour, there remains to be explained the undoubted fact that
all the more intense and gorgeous tints are manifested by the
animal life of the tropics; while in some groups, such as
butterflies and birds, there is a marked preponderance of
highly-coloured species. This is probably due to a variety of
causes, some of which we can indicate, while others remain
to be discovered. The luxuriant vegetation of the tropics
throughout the entire year affords so much concealment that
colour may there be safely developed to a much greater
extent than in climates where the trees are bare in winter,
during which season the struggle for existence is most severe,
and even the slightest disadvantage may prove fatal. Equally
important, probably, has been the permanence of favourable
conditions in the tropics, allowing certain groups to continue
dominant for long periods, and thus to carry out in one
unbroken line whatever developments of plumage or colour
may once have acquired an ascendency. Changes of climatal
conditions, and pre-eminently the glacial epoch, probably led
to the extinction of a host of highly-developed and finely-
coloured insects and birds in temperate zones, just as we
know that it led to the extinction of the larger and more
powerful mammalia which formerly characterised the tem-
perate zone in both hemispheres ; and this view is supported
by the fact that it is amongst those groups only which are
now exclusively tropical that all the more extraordinary
developments of ornament and colour are found. The obscure
local causes of colour to which we have referred will also
have acted most efficiently in regions where the climatal
condition remained constant, and where migration was unneces-
sary ; while whatever direct effect may be produced by light
or heat will necessarily have acted more powerfully within
the tropics. And lastly, all these causes have been in action
over an actually greater area in tropical than in temperate

1 These views have been restated and enforced by much fresh illustration
and argument in Darwinism, chap. x.

394 TROPICAL NATURE

zones ; while, estimated potentially, in proportion to their life-
sustaining power, the lands which enjoy a practically tropical
climate (extending as they do considerably beyond the geo-
graphical tropics) are very much larger than the temperate
regions of the earth.

Combining the effects of all these various causes, we are
quite able to understand the superiority of the tropical parts
of the globe, not only in the abundance and variety of their
forms of life, but also as regards the ornamental appendages
and vivid coloration which these forms present

VI

THE COLOURS OF PLANTS AND THE ORIGIN OF THE
COLOUR-SENSE

Source of Colouring Matter in Plants— Protective Coloration and Mimicry
in Plants— Attractive Colours of Fruits— Protective Colours of
Fruits— Attractive Colours of Flowers— Attractive Odours in Flowers
— Attractive Grouping of Flowers — Why Alpine Flowers are so beauti-
ful—Why Allied Species of Flowers differ in size and beauty— Absence
of Colour in Wind-fertilised Flowers— The same Theory of Colour
applicable to Animals and Plants — Relation of the Colours of Flowers
and their Geographical Distribution— Recent Views as to Direct
Action of Light on the Colours of Flowers and Fruits — On the Origin
of the Colour-sense: Supposed increase of Colour-perception within
the Historical Period— Concluding Remarks on the Colour-sense.

Source of Colouring Matter in Plants

THE colouring of plants is neither so varied nor so complex
as that of animals, and its explanation accordingly offers
fewer difficulties. The colours of foliage are, comparatively,
little varied, and can be traced in almost all cases to a special
pigment termed chlorophyll, to which is due the general green
colour of leaves ; but the recent investigations of Mr. Sorby
and others have shown that chlorophyll is not a simple green
pigment, but that it really consists of at least seven distinct
substances, varying in colour from blue to yellow and orange.
These differ in their proportions in the chlorophyll of differ-
ent plants ; they have different chemical reactions ; they are
differently affected by light ; and they give distinct spectra.
Mr. Sorby further states that scores of different colouring
matters are found in the leaves and flowers of plants, to some
of which appropriate names have been given, as erythrophyll,
which is red ; and phaiophyll, which is brown ; and many of

396 TROPICAL NATURE

these differ greatly from each other in their chemical com-
position. These inquiries are at present in their infancy, but
as the original term chlorophyll seems scarcely applicable
under the present aspect of the subject, it would perhaps
be better to introduce the analogous word chromophyll as
a general term for the colouring matters of the vegetable
kingdom.

Light has a much more decided action on plants than
on animals. The green colour of leaves is almost wholly
dependent on it; and although some flowers will become
fully coloured in the dark, others are decidedly affected by
the absence of light, even when the foliage is fully exposed to
it. Looking therefore at the numerous colouring matters
which are developed in the tissues of plants, the sensitiveness
of these pigments to light, the changes they undergo during
growth and development, and the facility with which new
chemical combinations are effected by the physiological pro-
cesses of plants as shown by the endless variety in the
chemical constitution of vegetable products, we have no
difficulty in comprehending the general causes which aid in
producing the colours of the vegetable world, or the extreme
variability of those colours. We may therefore here confine
ourselves to an inquiry into the various uses of colour in the
economy of plants, and this will generally enable us to under-
stand how it has become fixed and specialised in the several
genera and species of the vegetable kingdom.

Protective Coloration and Mimicry in Plants
In animals, as we have seen, colour is greatly influenced
by the need of protection from, or of warning to, their
numerous enemies, and by the necessity for identification
and easy recognition. Plants rarely need to be concealed,
and obtain protection either by their spines, their hardness,
their hairy covering, or their poisonous secretions. A very
few cases of what seem to be true protective colouring do,
however, exist, the most remarkable being that of the " stone
mesembryanthemum " of the Cape of Good Hope, which, in
form and colour, closely resembles the stones among which it
grows; and Dr. Burchell, who first discovered it, believes
that the juicy little plant thus generally escapes the notice

vi COLOURS OF PLANTS 897

of cattle and wild herbivorous animals. Mr. J. P. Mansel
Weale also noticed that many plants growing in the stony
Karoo have their tuberous roots above the soil, and these so
perfectly resemble the stones among which they grow that,
when not in leaf, it is almost impossible to distinguish them
(Nature, vol. iii. p. 507). A few cases of what seems to be
protective mimicry have also been noted, the most curious
being that of three very rare British fungi, found by Mr.
Worthington Smith, each in company with common species
which they so closely resembled that only a minute examina-
tion could detect the difference. One of the common species
is stated in botanical works to be " bitter and nauseous," so
that it is not improbable that the rare kind may escape being
eaten by being mistaken for an uneatable species, though
itself palatable. Mr. Mansel Weale also mentions a labiate
plant, the Ajuga ophrydis, of South Africa, as strikingly
resembling an orchid. This may be a means of attracting
insects to fertilise the flower in the absence of sufficient nectar
or other attraction in the flower itself ; and the supposition is
rendered more probable by this being the only species of the
genus Ajuga in South Africa. Many other cases of resem-
blances between very distinct plants have been noticed — as that
of some Euphorbias to Cacti; but these very rarely inhabit the
same country or locality, and it has not been proved that there
is in any of these cases the amount of inter-relation between
the species which is the essential feature of the protective
" mimicry " that occurs in the animal world.

The different colours exhibited by the foliage of plants
and the changes it undergoes during growth and decay,
appear to be due to the general laws already sketched out,
and to have little if any relation to the special requirements
of each species. But flowers and fruits exhibit definite and
well-pronounced tints, often varying from species to species,
and more or less clearly related to the habits and functions of
the plant. With the few exceptions already pointed out,
these may be generally classed as attractive colours.

Attractive Colours of Fruits

The seeds of plants require to be dispersed so as to reach
places favourable for germination and growth. Some are

398 TROPICAL NATURE

very minute and are carried abroad by the wind, or they are
violently expelled and scattered by the bursting of the con-
taining capsules. Others are downy or winged, and are
carried long distances by the gentlest breeze, or they are
hooked and stick to the fur of animals. But there is a large
class of seeds which cannot be dispersed in either of these
ways, and they are mostly contained in eatable fruits. These
fruits are devoured by birds or beasts, and the hard seeds
pass through their stomachs undigested, and, owing probably
to the gentle heat and moisture to which they have been sub-
jected, in a condition highly favourable for germination. The
dry fruits or capsules containing the first two classes of seeds
are rarely, if ever, conspicuously coloured, whereas the eatable
fruits almost invariably acquire a bright colour as they ripen,
while at the same time they become soft and often full of
agreeable juices. Our red haws and hips, our black elder-
berries, our blue sloes and whortleberries, our white mistletoe
and snowberry, and our orange sea-buckthorn, are examples
of the colour-sign of edibility ; and in every part of the world
the same phenomenon is found. Many such fruits are poison-
ous to man and to some animals, but they are harmless to
others ; and there is probably nowhere a brightly coloured
pulpy fruit which does not serve as food for some species of
bird or mammal.

Protective Colours of Fruits

The nuts and other hard fruits of large forest-trees, though
often greedily eaten by animals, are not rendered attractive
to them by colour, because they are not intended to be eaten.
This is evident, for the part eaten in these cases is the seed
itself, the destruction of which must certainly be injurious to
the species. Mr. Grant Allen, in his ingenious work on
Physiological Esthetics, well observes that the colours of all
such fruits are protective — green when on the tree, and thus
hardly visible among the foliage, but turning brown as they
ripen and fall on the ground, as filberts, chestnuts, walnuts,
beechnuts, and many others. It is also to be noted that
many of these are specially though imperfectly protected,
some by a prickly coat as in the chestnuts, or by a nauseous
covering as in the walnut ; and the reason why the protection

vr COLOURS OF PLANTS 899

is not carried farther is probably because it is not needed,
these trees producing such vast quantities of fruit, that, how-
ever many are eaten, more than enough are always left to
produce young plants. In the case of the attractively coloured
fruits, it is curious to observe how the seeds are always of
such a nature as to escape destruction when the fruit itself is
eaten. They are generally very small and comparatively
hard, as in the strawberry, gooseberry, and fig; if a little
larger, as in the grape, they are still harder and less eatable ;
in the fruit of the rose or (hip) they are disagreeably hairy ;
in the orange tribe excessively bitter. When the seeds are
larger, softer, and more eatable, they are protected by an
excessively hard and stony covering, as in the plum and
peach tribe ; or they are enclosed in a tough horny core, as
with crabs and apples. These last are much eaten by swine,
and are probably crushed and swallowed without bruising
the core or the seeds, which pass through their bodies
undigested. These fruits may also be swallowed by some of
the larger frugivorous birds, just as nutmegs are swallowed
by pigeons for the sake of the mace which encloses the nut,
and which by its brilliant red colour is an attraction as soon
as the fruit has split open, which it does upon the tree.

There is, however, one curious case of an attractively
coloured seed which has no soft eatable covering. The Abrus
precatoria, or " rosary bean," is a leguminous shrub or small
tree growing in many tropical countries, whose pods curl up
and split open on the tree, displaying the brilliant red seeds
within. It is very hard and glossy, and is said to be, as
no doubt it is, " very indigestible." It may be that birds,
attracted by the bright colour of the seeds, swallow them,
and that they pass through their bodies undigested, and so
get dispersed. If so it would be a case among plants analo-
gous to mimicry among animals — an appearance of edibility
put on to deceive birds for the plant's benefit. Perhaps it
succeeds only with young and inexperienced birds, and it
would have a better chance of success, because such deceptive
appearances are very rare among plants.

The smaller plants whose seeds simply drop upon the
ground, as in the grasses, sedges, composites, umbelliferae,
etc., always have dry and obscurely coloured capsules and

400 TROPICAL NATURE

small brown seeds. Others whose seeds are ejected by the
bursting open of their capsules, as with the oxalis and many
of the caryophyllacese, scrophulariacese, etc., have their seeds
very small and rarely or never edible.

It is to be remarked that most of the plants whose large-
seeded nuts cannot be eaten without destroying their germ-
inating power — as the oaks, beeches, and chestnuts — are
trees of large size which bear great quantities of fruit, and
that they are long lived and have a wide geographical range.
They belong to what are called dominant groups, and are
thus able to endure having a large proportion of their seeds
destroyed with impunity. It is a suggestive fact that they
are among the most ancient of known dicotyledonous plants —
oaks and beeches going back to the Cretaceous period with
little change of type, so that it is not improbable that they
may be older than any fruit-eating mammal adapted to feed
upon their fruits. The attractive coloured fruits on the other
hand, having so many special adaptations to dispersal by
birds and mammals, are probably of more recent origin.1
The apple and plum tribes are not known earlier than the
Miocene period ; and although the record of extinct vegetable
life is extremely imperfect, and the real antiquity of these
groups is no doubt very much greater, it is not improbable
that the comparative antiquity of the fruit-bearing and nut-
bearing trees may remain unchanged by further discoveries,
as has almost always happened as regards the comparative
antiquity of animal groups.

Attractive Colours of Flowers

The colours of flowers serve to render them visible and
recognisable by insects, which are attracted by secretions of
nectar or pollen. During their visits for the purpose of
obtaining these products, insects involuntarily carry the
pollen of one flower to the stigma of another, and thus effect
cross -fertilisation, which, as Mr. Darwin was the first to
demonstrate, immensely increases the vigour and fertility of
the next generation of plants. This discovery has led to
the careful examination of great numbers of flowers, and the

1 I owe this remark to Mr. Grant Allen, author of Physiological
Esthetics.

vi COLOURS OF PLANTS 401

result has been that the most wonderful and complex arrange-
ments have been found to exist, all having for their object to
secure that flowers shall not be self-fertilised perpetually, but
that pollen shall be carried, either constantly or occasionally,
from the flowers of one plant to those of another. Mr.
Darwin himself first worked out the details in orchids,
primulas, and some other groups, and hardly less curious
phenomena have since been found to occur even among some
of the most regularly -formed flowers. The arrangement,
length, and position of all the parts of the flower is now
found to have a purpose, and not the least remarkable por-
tion of the phenomenon is the great variety of ways in which
the same result is obtained. After the discoveries with
regard to orchids, it was to be expected that the irregular,
tubular, and spurred flowers should present various curious
adaptations for fertilisation by insect -agency. But even
among the open, cup -shaped, and quite regular flowers, in
which it seemed inevitable that the pollen must fall on the
stigma and produce constant self -fertilisation, it has been
found that this is often prevented by a physiological varia-
tion— the anthers constantly emitting their pollen either a
little earlier or a little later than the stigmas of the same
flower, or of other flowers on the same plant, were in the
best state to receive it ; and as individual plants in different
stations, soils, and aspects differ somewhat in the time of
flowering, the pollen of one plant would often be conveyed
by insects to the stigmas of some other plant in a condition
to be fertilised by it. This mode of securing cross-fertilisation
seems so simple and easy that we can hardly help wondering
why it did not always come into action, and so obviate the
necessity for those elaborate, varied, and highly complex
contrivances found perhaps in the majority of coloured
flowers. The answer to this of course is, that variation some-
times occurred most freely in one part of a plant's organisation
and sometimes in another, and that the benefit of cross-fertili-
sation was so great that any variation that favoured it was
preserved, and then formed the starting-point of a whole
series of further variations, resulting in those marvellous
adaptations for insect fertilisation which have given much of
their variety, elegance, and beauty to the floral world. For
2D

TROPICAL NATURE

details of these adaptations we must refer the reader to the
works of Darwin, Lubbock, Herman Miiller, and others. We
have here only to deal with the part played by colour, and
by those floral structures in which colour is most displayed.

Attractive Odours in Flowers

The sweet odours of flowers, like their colours, seem
to have been developed as an attraction or guide to insect
fertilisers, and the two phenomena are often complementary
to each other. Thus, many inconspicuous flowers, like the
mignonette and the sweet -violet, can be distinguished by
their odours before they attract the eye, and this may often
prevent their being passed unnoticed; while very showy
flowers, and especially those with variegated or spotted petals,
are seldom sweet. White, or very pale flowers, on the other
hand, are often excessively sweet, as exemplified by the
jasmine and clematis ; and many of these are only scented at
night, as is strikingly the case with the night-smelling stock,
our butterfly orchis (Habenaria chlorantha), the greenish-
yellow Daphne pontica, and many others. These white
flowers are mostly fertilised by night-flying moths, and those
which reserve their odours for the evening probably escape
the visits of diurnal insects, which would consume their
nectar without effecting fertilisation. The absence of odour
in showy flowers, and its preponderance among those that
are white, may be shown to be a fact by an examination of
the lists in Mr. Mongredien's work on hardy trees and shrubs.1
He gives a list of about 160 species with showy flowers, and
another list of sixty species with fragrant flowers ; but only
twenty of these latter are included among the showy species,
and these are almost all white flowered. Of the sixty species
with fragrant flowers, more than forty are white, and a
number of others have greenish, yellowish, or dusky and
inconspicuous flowers. The relation of white flowers to
nocturnal insects is also well shown by those which, like the
evening primroses, only open their large white blossoms after
sunset, while most of the yellow species remain open all day.
The red Martagon lily has been observed by Mr. Herman

x Trees and Shruts for English Plantations, by Augustus Mongredien.
Murray, 1870.

vi COLOURS OF PLANTS 403

Miiller to be fertilised by the humming-bird hawk moth,
which flies in the morning and afternoon, when the colours of
this flower, exposed to the nearly horizontal rays of the sun,
glow with brilliancy, and when it also becomes very sweet-
scented.

Attractive Grouping of Flowers

To the same need of conspicuousness the combination of
so many individually small flowers into heads and bunches is
probably due, producing such broad masses as those of the
elder, the guelder-rose, and most of the Umbelliferae, or such
elegant bunches as those of the lilac, laburnum, horse chest-
nut, and wistaria. In other cases minute flowers are gathered
into dense heads, as with Globularia, Jasione, clover, and all
the Composite ; and among the latter the outer flowers are
often developed into a ray, as in the sunflowers, the daisies,
and the asters, forming a starlike compound flower, which is
itself often produced in immense profusion.

Why Alpine Flowers are so beautiful

The beauty of Alpine flowers is almost proverbial. It
consists either in the increased size of the individual flowers
as compared with the whole plant, in increased intensity of
colour, or in the massing of small flowers into dense cushions
of bright colour ; and it is only in the higher Alps, above the
limit of forests and upwards towards the perpetual snow-line,
that these characteristics are fully exhibited. This effort at
conspicuousness under adverse circumstances may be traced
to the comparative scarcity of winged insects in the higher
regions, and to the necessity for attracting them from a dis-
tance. Amid the vast slopes of debris and the huge masses
of rock so prevalent in higher mountain regions, patches of
intense colour can alone make themselves visible and serve to
attract the wandering butterfly from the valleys. Mr. Herman
Miiller's careful observations have shown that in the higher
Alps bees and most other groups of winged insects are almost
wanting, while butterflies are tolerably abundant ; and he has
discovered that in a number of cases where a lowland flower
is adapted to be fertilised by bees, its Alpine ally has had its
structure so modified as to be adapted for fertilisation only

404 TROPICAL NATURE

by butterflies.1 But bees are always (in the temperate zone)
far more abundant than butterflies, and this will be another
reason why flowers specially adapted to be fertilised by the
latter should be rendered unusually conspicuous. We find,
accordingly, the yellow primroses and cowslips of the plains
replaced by pink and magenta -coloured Alpine species; the
straggling wild pinks of the lowlands by the masses of large
flowers in such mountain species as Dianthus alpinus and D.
glacialis; the saxifrages of the high Alps with bunches of
flowers a foot long as in Saxifraga longif olia and S. cotyledon,
or forming spreading masses of flowers as in S. oppositifolia ;
while the soapworts, silenes, and louseworts are equally superior
to the allied species of the plains.

Why Allied Species of Flowers differ in Size and Beauty
Again, Dr. Miiller has discovered that when there are
showy and inconspicuous species in the same genus of plants,
there is often a corresponding difference of structure, those
with large and showy flowers being quite incapable of self-
fertilisation, and thus depending for their very existence on
the visits of insects, while the others are able to fertilise
themselves should insects fail to visit them. We have
examples of this difference in Malva sylvestris, Epilobium
angustifolium, Polygonum bistorta, and Geranium pratense —
which have all large or showy flowers, and must be fertilised
by insects — as compared with Malva rotundifolia, Epilobium
parviflorum, Polygonum aviculare, and Geranium pusillum,
which have small or inconspicuous flowers, and are so con-
structed that if insects should not visit them they are able to
fertilise themselves.2

Absence of Colour in Wind-fertilised Flowers
As supplementing these curious facts, showing the relation
of colour in flowers to the need of the visits of insects to
fertilise them, we have the remarkable, and, on any other
theory, utterly inexplicable circumstance that in all the numer-
ous cases in which plants are fertilised by the agency of
the wind they never have specially coloured floral envel-
opes. Such are our pines, oaks, poplars, willows, beeches,
1 Nature, vol. xi. pp. 32, 110. » Ib., vol. ix. p. 164.

vi COLOURS OF PLANTS 405

and hazel, our nettles, grasses, sedges, and many others. In
some of these the male flowers are very conspicuous, as the
catkins of the willows, and these secrete honey and attract
numerous insects at a season when there are few other flowers,
and thus secure cross -fertilisation. Sedges and grasses are
also occasionally visited by insects.

The same Theory of Colour applicable to Animals and Plants
It may be thought that this absence of colour where it is
not wanted is opposed to the view maintained in the earlier
part of the preceding chapter, that colour is normal and is
constantly tending to appear in natural objects. It must be
remembered, however, that the green colour of foliage, due to
chlorophyll, prevails throughout the greater part of the vege-
table kingdom, and has, almost certainly, persisted through
long geological periods. It has thus acquired a fixity of
character which cannot be readily disturbed ; and, as a matter
of fact, we find that colour rarely appears in plants except in
association with a considerable modification of leaf -texture,
such as occurs in the petals and coloured sepals of flowers.
Wind -fertilised plants never have such specially organised
floral envelopes, and, in most cases, are entirely without a
calyx or corolla. The connection between modification of
leaf -structure and colour is further seen in the greater amount
and variety of colour in irregular than in regular flowers.
The latter, which are least modified, have generally uniform
or but slightly varied colours, while the former, which have
undergone great modification, present an immense range of
colour and marking, culminating in the spotted and varie-
gated flowers of such groups as the Scrophularinese and
Orchideae. The same laws as to the conditions of a maximum
production of colour are thus found to obtain both in plants
and animals.

Relation of the Colours of Flowers and their Geographical
Distribution

The adaptation of flowers to be fertilised by insects —
often to such an extent that the very existence of the species
depends upon it — has had an important influence on the dis-
tribution of plants and the general aspects of vegetation.

406 TROPICAL NATURE

The seeds of a particular species may be carried to another
country, may find there a suitable soil and climate, may grow
and produce flowers ; but if the insect which alone can fertilise
it should not inhabit that country, the plant cannot maintain
itself, however frequently it may be introduced or however
vigorously it may grow. Thus may probably be explained
the poverty in flowering-plants and the great preponderance
of ferns that distinguishes many oceanic islands, as well as
the deficiency of gaily -coloured flowers in others. New
Zealand is, in proportion to its total number of flowering-
plants, exceedingly poor in handsome flowers, and it is cor-
respondingly poor in insects, especially in bees and butterflies,
the two groups which so greatly aid in fertilisation. In both
these aspects it contrasts strongly with Southern Australia
and Tasmania in the same latitudes, where there is a profu-
sion of gaily -coloured flowers and an exceeding rich insect-
fauna. Another case is presented by the Galapagos islands,
which, though situated on the equator off the west coast of
South America, and with a tolerably luxuriant vegetation in
the damp mountain zone, yet produce hardly a single con-
spicuously-coloured flower; and this is correlated with, and
no doubt dependent on, an extreme poverty of insect life, not
one bee and only a single butterfly having been found there.

Again, there is reason to believe that some portion of the
large size and corresponding showiness of tropical flowers is
due to their being fertilised by very large insects and even
by birds. Tropical sphinx-moths often have their probosces
nine or ten inches long, and we find flowers whose tubes or
spurs reach about the same length, while the giant bees, and
the numerous flower-sucking birds, aid in the fertilisation of
flowers whose corollas or stamens are proportionately large.

Recent Views as to direct Action of Light on the Colours of
Flowers and Fruits

The theory that the brilliant colours of flowers and fruits
are due to the direct action of light has been supported by a
recent writer by examples taken from the arctic instead of
from the tropical flora. In the arctic regions vegetation is
excessively rapid during the short summer, and this is held
to be due to the continuous action of light throughout the

vi COLOURS OF PLANTS 407

long summer days. " The farther we advance towards the
north the more the leaves of plants increase in size, as if to
absorb a greater proportion of the solar rays. M. Grisebach
says that during a journey in Norway he observed that the
majority of deciduous trees had already, at the 60th degree
of latitude, larger leaves than in Germany, while M. Ch.
Martins has made a similar observation as regards the legu-
minous plants, cultivated in Lapland."1 The same writer goes
on to say that all the seeds of cultivated plants acquire a
deeper colour the farther north they are grown, white hari-
cots becoming brown or black, and white wheat becoming
brown, while the green colour of all vegetation becomes more
intense. The flowers also are similarly changed : those which
are white or yellow in central Europe becoming red or orange
in Norway. This is what occurs in the Alpine flora, and the
cause is said to be the same in both — the greater intensity of
the sunlight. In the one the light is more persistent, in the
other more intense because it traverses a thinner atmosphere.
Admitting the facts as above stated to be in themselves
correct, they do not by any means establish the theory
founded on them ; and it is curious that Grisebach, who has
been quoted by this writer for the fact of the increased size
of the foliage, gives a totally different explanation of the
more vivid .colours of arctic flowers. He says : " We see
flowers become larger and more richly coloured in proportion
as, by the increasing length of winter, insects become rarer,
and their co-operation in the act of fecundation is exposed to
more uncertain chances" (Vegetation du Globe, vol. i. p. 61 —
French translation). This is the theory here adopted to
explain the colours of Alpine plants, and we believe there are
many facts that will show it to be the preferable one. The
statement that the white and yellow flowers of temperate
Europe become red or golden in the arctic regions must, we
think, be incorrect. By roughly tabulating the colours of
the plants given by Sir Joseph Hooker2 as permanently
arctic, we find among fifty species with more or less con-
spicuous flowers, twenty -five white, twelve yellow, eight

1 Revue des Deux Mondes, 1877—" La Vegetation dans les hautes Lati-
tudes," par M. Tisserand.

2 "On the Distribution of Arctic Plants," Linn. Trans, vol. xxiii. (1862).

TROPICAL NATURE

purple or blue, three -lilac, and two red or pink, showing a
very similar proportion of white and yellow flowers to what
obtains farther south.

We have, however, a remarkable flora in the southern
hemisphere, which affords a crucial test of the theory of greater
intensity of light being the direct cause of brilliantly-coloured
flowers. The Auckland and Campbell's islands, south of New
Zealand, are in the same latitude as the middle and the south
of England, and the summer days are therefore no longer
than with us. The climate, though cold, is very uniform,
and the weather "very rainy and stormy." It is evident,
then, that there can be no excess of sunshine above what we
possess, yet in a very limited flora there are a number of
flowers which — Sir Joseph Hooker states — are equal in
brilliancy to those of the arctic flora. These consist of
brilliant gentians, handsome veronicas, large and magnificent
Composite with purple flowers, bright ranunculi, showy
Umbelliferse, and the golden -flowered Chrysobactron Eossii,
one of the finest of the Asphodeleee. l All these fine plants,
it must be remembered, are peculiar to these islands, and
have therefore been developed under the climatal conditions
that prevail there ; and as we have no reason to suppose that
these conditions have undergone any recent change, we may
be quite sure that an excess of light has had nothing to do
with the development of these exceptionally bright and hand-
some flowers. Unfortunately we have no information as to
the insects of these islands, but from their scarcity in New
Zealand we can hardly expect them to be otherwise than very
scarce. There are, however, two species of honey -sucking
birds (Prosthemadera and Anthornis), as well as a small
warbler (Myiomoira); and we may be pretty sure that the
former at least visit these large and handsome flowers, and
so effect their fertilisation. The most abundant tree on the
islands is a species of Metrosideros, and we know that trees
of this genus are common in the Pacific islands, where they
are almost certainly fertilised by the same family of Meli-
phagidse or honey-sucking birds.

I have now concluded this sketch of the general pheno-
1 Coloured figures of all these plants are given in the Flora Antarctica, vol. L

vi COLOURS OF PLANTS 409

mena of colour in the organic world. I have shown reasons
for believing that its presence, in some of its infinitely-varied
hues, is more probable than its absence, and that variation of
colour is an almost necessary concomitant of variation of struc-
ture, of development, and of growth. It has also been shown
how colour has been appropriated and modified both in the
animal and vegetable worlds for the advantage of the species
in a great variety of ways, and that there is no need to call
in the aid of any other laws than those of organic develop-
ment and " natural selection " to explain its countless modifi-
cations. From the point of view here taken, it seems at once
improbable and unnecessary that the lower animals should
have the same delicate appreciation of the infinite variety
and beauty, of the delicate contrasts and subtle harmonies of
colour, which are possessed by the more intellectual races of
mankind, since even the lower human races do not possess it.
All that seems required in the case of animals is a perception
of distinctness or contrast of colours; and the dislike of so
many creatures to scarlet may perhaps be due to the rarity
of that colour in nature, and to the glaring contrast it offers
to the sober greens and browns which form the general cloth-
ing of the earth's surface, though it may also have a direct
irritating effect on the retina.

The general view of the subject now given must convince
us that, so far from colour being — as it has sometimes been
thought to be — unimportant, it is intimately connected with
the very existence of a large proportion of the species of the
animal and vegetable worlds. The gay colours of the butter-
fly and of the Alpine flower which it unconsciously fertilises
while seeking for its secreted honey, are each beneficial to its
possessor, and have been shown to be dependent on the same
class of general laws as those which have determined the
form, the structure, and the habits of every living thing.
The complex laws and unexpected relations which we have
seen to be involved in the production of the special colours of
flower, bird, and insect must give them an additional interest
for every thoughtful mind; while the knowledge that, in
all probability, each style of coloration, and sometimes the
smallest details, have a meaning and a use must add a new
charm to the study of nature.

410 TROPICAL NATURE

ON THE ORIGIN OF THE COLOUR-SENSE

Throughout the preceding discussion we have accepted
the subjective phenomena of colour — that is, our perception
of varied hues and the mental emotions excited by them — as
ultimate facts needing no explanation. Yet they present
certain features well worthy of attention, a brief considera-
tion of which will form a fitting sequel to the present essay.

The perception of colour seems, to the present writer, the
most wonderful and the most mysterious of our sensations.
Its extreme diversities and exquisite beauties seem out of
proportion to the causes that are supposed to have produced
them, or the physical needs to which they minister. If we
look at pure tints of red, green, blue, and yellow, they appear
so absolutely contrasted and unlike each other, that it is
almost impossible to believe (what we nevertheless know to
be the fact) that the rays of light producing these very dis-
tinct sensations differ only in wave-length and rate of vibra-
tion, and that there is from one to the other a continuous
series and gradation of such vibrating waves. The positive
diversity we see in them must then depend upon special
adaptations in ourselves ; and the question arises, For what
purpose have our visual organs and mental perceptions become
so highly specialised in this respect?

When the sense of sight was first developed in the animal
kingdom, we can hardly doubt that what was perceived was
light only, and its more or less complete withdrawal. As the
sense became perfected, more delicate gradations of light and
shade would be perceived, and there seems no reason why a
visual capacity might not have been developed as perfect as
our own, or even more so in respect of light and shade, but
entirely insensible to differences of colour, except in so far
as these implied a difference in the quantity of light. The
world would in that case appear somewhat as we see it in
good stereoscopic photographs ; and we all know how ex-
quisitely beautiful such pictures are, and how completely
they give us all requisite information as to form, surface-
texture., solidity, and distance, and even to some extent as to
colour, for almost all colours are distinguishable in a photo-
graph by some differences of tint, and it is quite conceivable

vi ORIGIN OF THE COLOUR-SENSE 411

that visual organs might exist which would differentiate what
we term colour by delicate gradations of some one charac-
teristic neutral tint. Now such a capacity of vision would
be simple as compared with that which we actually possess,
which, besides distinguishing infinite gradations of the quan-
tity of light, distinguishes also, by a totally distinct set of
sensations, gradations of quality, as determined by differences
of wave-lengths or rate of vibration. At what grade in
animal development this new and more complex sense first
began to appear we have no means of determining. The
fact that the higher vertebrates, and even some insects, dis-
tinguish what are to us diversities of colour by no means
proves that their sensations of colour bear any resemblance
whatever to ours. An insect's capacity to distinguish red
from blue or yellow may be (and probably is) due to percep-
tions of a totally distinct nature, and quite unaccompanied by
any of that sense of enjoyment or even of radical distinctness
which pure colours excite in us. Mammalia and birds, whose
structure and emotions are so similar to our own, do probably
receive somewhat similar impressions of colour ; but we have
no evidence to show that they experience pleasurable emotions
from colour itself when not associated with the satisfaction of
their wants or the gratification of their passions.

The primary necessity which led to the development of
the sense of colour was probably the need of distinguishing
objects much alike in form and size, but differing in important
properties, such as ripe and unripe, or eatable and poisonous
fruits, flowers with honey or without, the sexes of the same
or of closely allied species. In most cases the strongest con-
trast would be the most useful, especially as the colours of
the objects to be distinguished would form but minute spots
or points when compared with the broad masses of tint of
sky, earth, or foliage against which they would be set.

Throughout the long epochs in which the sense of sight
was being gradually developed in the higher animals, their
visual organs would be mainly subjected to two groups of
rays — the green from vegetation, and the blue from the sky.
The immense preponderance of these over all other groups of
rays would naturally lead the eye to become specially adapted
for their perception ; and it is quite possible that at first

412 TROPICAL NATURE

these were the only kinds of light- vibrations which could be
perceived at all. When the need for differentiation of colour
arose, rays of greater and of smaller wave-lengths would
necessarily be made use of to excite the new sensations required,
and we can thus understand why green and blue form the
central portion of the visible spectrum, and are the colours
which are most agreeable to us in large surfaces ; while at its
two extremities we find yellow, red, and violet— colours
which we best appreciate in smaller masses, and when con-
trasted with the other two, or with light neutral tints. We
have here probably the foundations of a natural theory of
harmonious colouring, derived from the order in which our
colour-sensations have arisen and the nature of the emotions
with which the several tints have been always associated.
The agreeable and soothing influence of green light may be
in part due to the green rays having little heating power ;
but this can hardly be the chief cause, for the blue and violet,
though they contain less heat, are not generally felt to be so
cool and sedative. But when we consider how dependent are
all the higher animals on vegetation, and that man himself
has been developed in the closest relation to it, we shall find,
probably, a sufficient explanation. The green mantle with
which the earth is overspread caused this one colour to pre-
dominate over all others that meet our sight, and to be almost
always associated with the satisfaction of human wants.
Where the grass is greenest, and vegetation most abundant
and varied, there has man always found his most suitable
dwelling-place. In such spots hunger and thirst are unknown,
and the choicest productions of nature gratify the appetite
and please the eye. In the greatest heats of summer, cool-
ness, shade, and moisture are found in the green forest glades,
and we can thus understand how our visual apparatus has
become especially adapted to receive pleasurable and soothing
sensations from this class of rays.

Supposed increase of Colour-perception within the Historical Period
Some writers believe that our power of distinguishing
colours has increased even in historical times. The subject
has attracted the attention of German philologists, and I have
been furnished by a friend with some notes from a work of

vi ORIGIN OF THE COLOUR-SENSE 413

the late Lazarus Geiger, entitled, Zur Entwickelungs-geschicUe
der Menschheit (Stuttgart, 1871). According to this writer it
appears that the colour of grass and foliage is never alluded to
as a beauty in the Vedas or the Zendavesta, though these
productions are continually extolled for other properties.
Blue is described by terms denoting sometimes green, some-
times black, showing that it was hardly recognised as a
distinct colour. The colour of the sky is never mentioned in
the Bible, the Vedas, the Homeric poems, or even in the
Koran. The first distinct allusion to it known to Geiger is
in an Arabic work of the ninth century. "Hyacinthine
locks" are black locks, and Homer calls iron "violet-
coloured." Yellow was often confounded with green, but,
along with red, it was one of the earliest colours to receive a
distinct name. Aristotle names three colours in the rainbow
— red, yellow, and green. Two centuries earlier Xenophanes
had described the rainbow as purple, reddish, and yellow.
The Pythagoreans admitted four primary colours — white,
black, red, and yellow; the Chinese the same, with the
addition of green.

Simultaneously with the first publication of this essay in
Macmillan's Magazine, there appeared in the Nineteenth Century
an article by Mr. Gladstone on the Colour-sense, chiefly as
exhibited in the poems of Homer. He shows that the few
colour -terms used by Homer are applied to such different
objects that they cannot denote colours only, as we perceive
and differentiate them, but seem more applicable to different
intensities of light and shade. Thus, to give one example,
the word porphureos is applied to clothing, to the rainbow,
to blood, to a cloud, to the sea, and to death ; and no one
meaning will suit all these applications except comparative
darkness. In other cases the same thing has many different
epithets applied to it according to its different aspects or
conditions ; and as the colours of objects are generally in-
dicated in ancient writings by comparative rather than by
abstract terms, — as wine-colour, fire-colour, bronze-colour, etc.,
— it becomes still more difficult to determine in any par-
ticular case what colour was really meant. Mr. Gladstone's
general conclusion is, that the archaic man had a positive
perception only of degrees of light and darkness, and that in

414 TROPICAL NATURE

Homer's time he had advanced to the imperfect discrimina-
tion of red and yellow, but no further ; the green of grass
and foliage or the blue of the sky being never once referred to.
These curious facts cannot, however, be held to prove so
recent an origin for colour -sensations as they would at first
sight appear to do, because we have seen that both flowers
and fruits have become diversely coloured in adaptation to
the visual powers of insects, birds, and mammals. Red
being a very common colour of ripe fruits which attract birds
to devour them and thus distribute their seeds, we may be
sure that the contrast of red and green is to them very well
marked. It is indeed just possible that birds may have a
more advanced development of the colour-sense than mam-
mals, because the teeth of the latter commonly grind up and
destroy the seeds of the larger fruits and nuts which they
devour, and which are not usually coloured ; but the irritat-
ing effect of bright colours on some of them does not support
this view. It seems most probable, therefore, that man's
perception of colour in the time of Homer was little if any
inferior to what it is now, but that, owing to a variety of
causes, no precise nomenclature of colours had become estab-
lished. One of these causes probably was, that the colours
of the objects of most importance, and those which were most
frequently referred to in songs and poems, were uncertain
and subject to variation. Blood was light or dark red, or
when dry, blackish ; iron was gray or dark or rusty ; bronze
was shining or dull ; foliage was of all shades of yellow,
green, or brown ; and horses or cattle had no one distinctive
colour. Other objects, as the sea, the sky, and wine, changed
in tint according to the light, the time of day, and the mode
of viewing them ; and thus colour, indicated at first by refer-
ence to certain coloured objects, had no fixity. Things which
had more definite and purer colours — as certain species of
flowers, birds, and insects — were probably too insignificant or
too much despised to serve as colour-terms ; and even these
often vary, either in the same or in allied species, in a manner
which would render their use unsuitable. Colour-names,
being abstractions, must always have been a late development
in language, and their comparative unimportance in an early
state of society and of the arts would still further retard their

vi ORIGIN OF THE COLOUR-SENSE 415

appearance ; and this seems quite in accordance with the vari-
ous facts set forth by Mr. Gladstone and the other writers
referred to. The fact that colour-blindness is so prevalent
even now is, however, an indication that the fully-developed
colour-sense is not of primary importance to man. If it had
been so, natural selection would long ago have eliminated the
disease itself, and its tendency to recur would hardly be so
strong as it appears to be.

Concluding Remarks on the Colour-sense
The preceding considerations enable us to comprehend
both why a perception of difference of colour has become
developed in the higher animals, and also why colours require
to be presented or combined in varying proportions in order
to be agreeable to us. But they hardly seem to afford a
sufficient explanation either of the wonderful contrasts and
total unlikeness of the sensations produced in us by the chief
primary colours, or of the exquisite charm and pleasure we
derive from colour itself, as distinguished from variously-
coloured objects, in the case of which association of ideas
comes into play. It is hardly conceivable that the material
uses of colour to animals and to ourselves required such very
distinct and powerfully-contrasted sensations ; and it is still
less conceivable that a sense of delight in colour per se should
have been necessary for our utilisation of it.

The emotions excited by colour and by music alike seem
to rise above the level of a world developed on purely utili-
tarian principles.

VII

Indications of Man's Extreme Antiquity — Antiquity of Intellectual Man —
Sculptures on Easter Island — North American Earthworks — The
Great Pyramid — Conclusion.

MANY now living remember the time (for it is little more than
twenty years ago) when the antiquity of man, as now under-
stood, was universally discredited. Not only theologians,
but even geologists, then taught us that man belonged
altogether to the existing state of things ; that the extinct
animals of the Tertiary period had finally disappeared, and
that the earth's surface had assumed its present condition,
before the human race first came into existence. So pre-
possessed were even scientific men with this idea — which yet
rested on purely negative evidence, and could not be sup-
ported by any arguments of scientific value — that numerous
facts which had been presented at intervals for half a century,
all tending to prove the existence of man at very remote
epochs, were silently ignored ; and, more than this, the
detailed statements of three distinct and careful observers,
confirming each other, were rejected by a great scientific
Society as too improbable for publication, only because they
proved (if they were true) the coexistence of man with extinct
animals.2

1 This formed part of the author's address to the Biological Section of the
British Association at Glasgow in 1876.

2 In 1854 (?) a communication from the Torquay Natural History Society
confirming previous accounts by Mr. Godwin-Austen, Mr. Vivian, and the
Rev. Mr. M'Enery, that worked flints occurred in Kent's Hole with remains of
extinct species, was rejected as too improbable for publication. See Lubbock's
Prehistoric Times, 2d ed., p. 306.

vii THE ANTIQUITY AND ORIGIN OF MAN 417

But this state of belief in opposition to facts could not
long continue. In 1859 a few of our most eminent geologists
examined for themselves into the alleged occurrence of flint
implements in the gravels of the north of France, which had
been made public fourteen years before, and found them
strictly correct. The caverns of Devonshire were about the
same time carefully examined by equally eminent observers,
and were found fully to bear out the statements of those
who had published their results eighteen years before. Flint
implements began to be found in all suitable localities in
the south of England, when carefully searched for, often in
gravels of equal antiquity with those of France. Caverns
giving evidence of human occupation at various remote
periods were explored in Belgium and the south of France —
lake-dwellings were examined in Switzerland — refuse-heaps in
Denmark — and thus a whole series of remains have been
discovered carrying back the history of mankind from the
earliest historic periods to a long distant past.

The antiquity of the races thus discovered cannot be
measured in years ; but it may be approximately determined
by the successively earlier and earlier stages of civilisation
through which we can trace them, and by the changes in
physical geography and of animal and vegetable life that
have since occurred. As we go back metals soon disappear,
and we find only tools and weapons of stone and of bone.
The stone weapons get ruder and ruder ; pottery, and then
the bone implements, cease to occur; and in the earliest
stage we find only chipped flints of rude design, though
still of unmistakably human workmanship. In like manner
domestic animals disappear as we go backward ; and though
the dog seems to have been the earliest, it is doubtful
whether the makers of the ruder flint implements of the
gravels possessed even this. Still more important as a
measure of time are the changes in the distribution of
animals, indicating changes of climate, which have occurred
during the human period. At a comparatively recent epoch
in the record of prehistoric times we find that the Baltic
was far salter than it is now and produced abundance of
oysters, and that Denmark was covered with pine 'forests
inhabited by Capercailzies, such as now only occur farther
2E

418 TROPICAL NATURE

north in Norway. A little earlier we find that reindeer
were common even in the south of France ; and still earlier
this animal was accompanied by the mammoth and woolly
rhinoceros, by the arctic glutton, and by huge bears and
lions of extinct species. The presence of such animals implies
a change of climate ; and both in the caves and gravels we
find proofs of a much colder climate than now prevails in
Western Europe. Even more remarkable are the changes
of the earth's surface which have been effected during man's
occupation of it. Many extensive valleys in England and
France are believed by the best observers to have been
deepened at least a hundred feet ; caverns now far out of the
reach of any stream must for a long succession of years have
had streams flowing through them, at least in times of
floods ; and this often implies that vast masses of solid rock
have since been worn away. In Sardinia land has risen at
least 300 feet since men lived there who made pottery and
probably used fishing-nets ; * while in Kent's Cavern remains
of man are found buried beneath two separate beds of
stalagmite, each having a distinct texture, and each covering
a deposit of cave -earth having well-marked differential
characters, while each contains a distinct assemblage of
extinct animals.

Such, briefly, are the results of the evidence that has
been rapidly accumulating for about fifteen years, as to
the antiquity of man; and it has been confirmed by so
many discoveries of a like nature in all parts of the globe,
and especially by the comparison of the tools and weapons
of prehistoric man with those of modern savages (so that
the use of even the rudest flint implements has become
quite intelligible), that we can hardly wonder at the vast
revolution effected in public opinion. Not only is the
belief in man's vast and still unknown antiquity universal
among men of science, but it is hardly disputed by any well-
informed theologian ; and the present generation of science-
students must, we should think, be somewhat puzzled to
understand what there was in the earliest discoveries that
should have aroused such general opposition, and been met
with such universal incredulity.

1 Lyell's Antiquity of Man, 4th ed., p. 115.

vii THE ANTIQUITY AND ORIGIN OF MAN 419

But the question of the mere "Antiquity of Man"
almost sank into insignificance at a very early period of
the inquiry, in comparison with the far more momentous
and more exciting problem of the development of man from
some lower animal form, which the theories of Mr. Darwin
and of Mr. Herbert Spencer soon showed to be inseparably
bound up with it. This has been, and to some extent still
is, the subject of fierce conflict ; but the controversy as to the
fact of such development is now almost at an end, since one
of the most talented representatives of Catholic theology,
and an anatomist of high standing — Professor Mivart — fully
adopts it as regards physical structure, reserving his opposi-
tion for those parts of the theory which would deduce man's
whole intellectual and moral nature from the same source and
by a similar mode of development.

Never, perhaps, in the whole history of science or philo-
sophy has so great a revolution in thought and opinion been
effected as in the twelve years from 1859 to 1871, the
respective dates of publication of Mr. Darwin's Origin of
Species and Descent of Man. Up to the commencement
of this period the belief in the independent creation or
origin of the species of animals and plants, and the very
recent appearance of man upon the earth, were, practically,
universal. Long before the end of it these two beliefs had
utterly disappeared, not only in the scientific world, but
almost equally so among the literary and educated classes
generally. The belief in the independent origin of man held
its ground somewhat longer; but the publication of Mr.
Darwin's great work gave even that its deathblow, for hardly
any one capable of judging of the evidence now doubts the
derivative nature of man's bodily structure as a whole,
although many believe that his mind, and even some of his
physical characteristics, may be due to the action of other
forces than have acted in the case of the lower animals.

We need hardly be surprised, under these circumstances,
if there has been a tendency among men of science to pass
from one extreme to the other ; from a profession (so few
years ago) of total ignorance as to the mode of origin of all
living things, to a claim to almost complete knowledge of the
whole progress of the universe, from the first speck of living

420 TROPICAL NATURE

protoplasm up to the highest development of the human
intellect. Yet this is really what we have seen in the last
sixteen years. Formerly difficulties were exaggerated, and it
was asserted that we had not sufficient knowledge to venture
on any generalisations on the subject. Now difficulties are set
aside, and it is held that our theories are so well established
and so far-reaching that they explain and comprehend all
nature. It is not long ago (as I have already reminded
you) since facts were contemptuously ignored, because they
favoured our now popular views; at the present day it
seems to me that facts which oppose them hardly receive
due consideration. And as opposition is the best incentive
to progress, and it is not well even for the best theories to
have it all their own way, I propose to direct your attention
to a few such facts, and to the conclusions that seem fairly
deducible from them.

Indications of Man's Extreme Antiquity
It is a curious circumstance that, notwithstanding the
attention that has been directed to the subject in every part
of the world, and the numerous excavations connected with
railways and mines, which have offered such facilities for
geological discovery, no advance whatever has been made for
a considerable number of years in detecting the time or mode
of man's origin. The Palaeolithic flint weapons first dis-
covered in the north of France more than thirty years ago
are still the oldest undisputed proofs of man's existence ;
and amid the countless relics of a former world that have
been brought to light, no evidence of any one of the links
that must have connected man with the lower animals has
yet appeared.

It is, indeed, well known that negative evidence in
geology is of very slender value; and this is, no doubt,
generally the case. The circumstances here are, however,
peculiar, for many converging lines of evidence show that,
on the theory of development by the same laws which have
determined the development of the lower animals, man must
be immensely older than any traces of him yet discovered.
As this is a point of great interest we must devote a few
moments to its consideration.

vii THE ANTIQUITY AND ORIGIN OF MAN 421

1. The most important difference between man and such
of the lower animals as most nearly approach him is un-
doubtedly in the bulk and development of his brain, as
indicated by the form and capacity of the cranium. We
should therefore anticipate that these earliest races, who were
contemporary with the extinct animals and used rude stone
weapons, would show a marked deficiency in this respect.
Yet the oldest known crania (those of the Engis and Cro-
Magnon caves) show no marks of degradation. The former
does not present so low a type as that of most existing
savages, but is (to use the words of Professor Huxley) "a
fair average human skull, which might have belonged to a
philosopher, or might have contained the thoughtless brains
of a savage." The latter are still more remarkable, being
unusually large and well-formed. Dr. Pruner-Bey states that
they surpass the average of modern European skulls in
capacity, while their symmetrical form, without any trace
of prognathism, compares favourably not only with those of
the foremost savage races, but with many civilised nations
of modern times.

One or two other crania of much lower type, but of less
antiquity than this, have been discovered; but they in no
way invalidate the conclusion which so highly developed a
form at so early a period implies, viz. that we have as yet
made a hardly perceptible step towards the discovery of any
earlier stage in the development of man.

2. This conclusion is supported and enforced by the
nature of many of the works of art found even in the oldest
cave-dwellings. The flints are of the old chipped type, but
they are formed into a large variety of tools and weapons —
such as scrapers, awls, hammers, saws, lances, etc., implying
a variety of purposes for which these were used, and a
corresponding degree of mental activity and civilisation.
Numerous articles of bone have also been found, including
well- formed needles ; implying that skins were sewn together,
and perhaps even textile materials woven into cloth. Still
more important are the numerous carvings and drawings
representing a variety of animals, including horses, reindeer,
and even a mammoth, executed with considerable skill on
bone, reindeer- horns, and mammoth -tusks. These, taken

422 TROPICAL NATURE

together, indicate a state of civilisation much higher than
that of the lowest of our modern savages, while they are
quite compatible with a considerable degree of mental ad-
vancement, and lead us to believe that the crania of Engis
and Cro-Magnon are not exceptional, but fairly represent the
characters of the race. If we further remember that these
people lived in Europe under the unfavourable conditions of
a sub-arctic climate, we shall be inclined to agree with Dr.
Daniel Wilson that it is far easier to produce evidences of
deterioration than of progress, in instituting a comparison
between the contemporaries of the mammoth and later
prehistoric races of Europe or savage nations of modern
times.1

3. Yet another important line of evidence as to the
extreme antiquity of the human type has been brought
prominently forward by Professor Mivart.2 He shows, by a
careful comparison of all parts of the structure of the body,
that man is related not to any one', but almost equally to
many of the existing apes — to the orang, the chimpanzee,
the gorilla, and even to the gibbons, in a variety of ways ;
and these relations and differences are so numerous and so
diverse that, on the theory of evolution, the ancestral form
which ultimately developed into man must have diverged
from the common stock whence all these various forms and
their extinct allies originated. But so far back as the
Miocene deposits of Europe we find the remains of apes
allied to these various forms, and especially to the gibbons ;
so that in all probability the special line of variation which
led up to man branched off at a still earlier period. And
these early forms, being the initiation of a far higher type,
and having to develop by natural selection into so specialised
and altogether distinct a creature as man, must have risen at
a very early period into the position of a dominant race, and
spread in dense waves of population over all suitable portions
of the great continent — for this, on Mr. Darwin's hypothesis,
is essential to developmental progress through the agency of
natural selection.

Under these circumstances we might certainly expect to

1 Prehistoric Man, 3d ed., vol. i. p. 117.
? Man and Apes, pp. 171-193.

vii THE ANTIQUITY AND ORIGIN OF MAN 423

find some relics of these earlier forms of man along with
those of animals, which were presumably less abundant.
Negative evidence of this kind is not very weighty, but still it
has some value. It has been suggested that as apes are mostly
tropical, and anthropoid apes are now confined almost ex-
clusively to the vicinity of the equator, we should expect the
ancestral forms of man to have inhabited these same localities
— West Africa and the Malay islands. But this objection is
hardly valid, because existing anthropoid apes are wholly
dependent on a perennial supply of easily accessible fruits,
which is only found near the equator ; while not only had
the south of Europe an almost tropical climate in Miocene
times, but we must suppose even the earliest ancestors of
man to have been terrestrial and omnivorous, since it must
have taken ages of slow modification to have produced the
perfectly erect form, the short arms, and the wholly non-
prehensile foot,1 which so strongly differentiate man from
the arboreal apes.

The conclusion which I think we must arrive at is, that if
man has been developed from a common ancestor with all
existing apes, and by no other agencies than such as have affected
their development, then he must have existed, in something
approaching his present form, during the Tertiary period —
and not merely existed, but predominated in numbers,
wherever suitable conditions prevailed. If, then, continued
researches in all parts of Europe and Asia fail to bring to
light any proofs of his presence, it will be at least a pre-
sumption that he came into existence at a much later date,
and by a much more rapid process of development. In that
case it will be a fair argument that, just as he is in his
mental and moral nature, his capacities and aspirations, so
infinitely raised above the brutes, so his origin is due, in part,

1 The common statement of travellers as to savages having great prehensile
power in the toes has been adopted by some naturalists as indicating an ap-
proach to the apes. But this notion is founded on a complete misconception.
Savages pick up objects with their feet, it is true, but always by a lateral
motion of the toes, which we should equally possess if we never wore shoes or
stockings. In no savage have I ever seen the slightest approach to opposa-
bility of the great toe, which is the essential distinguishing feature of apes ;
nor have I ever seen it stated that any variation in this direction has been
detected in the anatomical structure of the foot of the lower races.

424 TROPICAL NATURE

to distinct and higher agencies than such as have affected
their development.

Antiquity of Intellectual Man

There is yet another line of inquiry bearing upon this
subject to which I wish to call your attention. It is a some-
what curious fact that, while all modern writers admit the
great antiquity of man, most of them maintain the very
recent development of his intellect, and will hardly con-
template the possibility of men equal in mental capacity to
ourselves having existed in prehistoric times. This question
is generally assumed to be settled by such relics as have been
preserved of the manufactures of the older races, showing
a lower and lower state of the arts ; by the successive
disappearance in early times of iron, bronze, and pottery;
and by the ruder forms of the older flint implements. The
weakness of this argument has been well shown by Mr.
Albert Mott in his very original but little-known presidential
address to the Literary and Philosophical Society of Liver-
pool in 1873. He maintains that " our most distant glimpses
of the past are still of a world peopled as now with men both
civilised and savage," and " that we have often entirely mis-
read the past by supposing that the outward signs of civilisa-
tion must always be the same, and must be such as are found
among ourselves." In support of this view he adduces a
variety of striking facts and ingenious arguments, a few of
which I will briefly summarise.

Sculptures on Easter Island

On one of the most remote islands of the Pacific — Easter
island— 2000 miles from South America, 2000 from the
Marquesas, and more than 1000 from the Gambier islands,
are found hundreds of gigantic stone images, now mostly in
ruins. They are often forty feet high, while some seem to
have been much larger, the crowns on their heads, cut out of
a red stone, being sometimes ten feet in diameter, while even
the head and neck of one is said to have been twenty feet
high.1 These images once all stood erect on extensive stone
platforms.

1 Journ. of Roy. Geog. Soc., 1870, pp. 177, 178.

vii THE ANTIQUITY AND ORIGIN OF MAN 425

The island containing these remarkable works of art has
only an area of about thirty square miles, or considerably less
than Jersey. Now, as one of the smallest images (eight feet
high) weighs four tons, the largest must weigh over a
hundred tons, if not much more ; and the existence of such
vast works implies a large population, abundance of food, and
an established government. Yet how could these coexist on
a mere speck of land wholly cut off from the rest of the
world ? Mr. Mott maintains that these facts necessarily
imply the power of regular communication with larger islands
or a continent, the arts of navigation, and a civilisation much
higher than now exists in any part of the Pacific. Very
similar remains in other islands scattered widely over the
Pacific add weight to this argument.

North American Earthworks

The next example is that of the ancient mounds and
earthworks of the North American continent, the bearing of
which is even more significant. Over the greater part of the
extensive Mississippi valley, four well-marked classes of these
earthworks occur. Some are camps, or works of defence,
situated on bluffs, promontories, or isolated hills ; others are
vast inclosures in the plains and lowlands, often of geometric
forms, and having attached to them roadways or avenues
often miles in length ; a third are mounds corresponding to
our tumuli, often seventy to ninety feet high, and some of
them covering acres of ground ; while a fourth group consists
of representations of various animals modelled in relief on a
gigantic scale, and occurring chiefly in an area somewhat to
the north-west of the other classes, in the plains of Wisconsin.

The first class — the camps or fortified inclosures — re-
semble in general features the ancient camps of our own
islands, but far surpass them in extent. Fort Hill, in Ohio,
is surrounded by a wall and ditch a mile and a half in length,
part of the way cut through solid rock. Artificial reservoirs
for water were made within it, while at one extremity, on a
more elevated point, a keep is constructed with its separate
defences and water-reservoirs. Another, called Clark's Work,
in the Scioto valley, which seems to have been a fortified
town, incloses an area of 127 acres, the embankments measur-

426 TROPICAL NATURE

ing three miles in length, and containing not less than three
million cubic feet of earth. This area incloses numerous
sacrificial mounds and symmetrical earthworks, in which
many interesting relics and works of art hav^e been found.

The second class — the sacred inclosures — may be compared
for extent and arrangement with Avebury or Karnak, but
are in some respects even more remarkable. One of these
at Newark, Ohio, covers an area of several miles, with its
connected groups of circles, octagons, squares, ellipses, and
avenues on a grand scale, and formed by embankments from
twenty to thirty feet in height. Other similar works occur
in different parts of Ohio ; and by accurate survey it is found,
not only that the circles are true, though some of them are
one-third of a mile in diameter, but that other figures are
truly square, each side being over 1000 feet long; and, what
is still more important, the dimensions of some of these
geometrical figures, in different parts of the country and
seventy miles apart, are identical. Now this proves the use,
by the builders of these works, of some standard measures of
length ; while the accuracy of the squares, circles, and, in a
less degree, of the octagonal figures, shows a considerable
knowledge of rudimentary geometry and some means of
measuring angles. The difficulty of drawing such figures on
a large scale is much greater than any one would imagine
who has not tried it ; and the accuracy of these is far beyond
what is necessary to satisfy the eye. We must, therefore,
impute to the builders the wish to make these figures as
accurate as possible, and this wish is a greater proof of
habitual skill and intellectual advancement than even the
ability to draw such figures. If, then, we take into account
this ability and this love of geometric truth, and further
consider the dense population and civil organisation implied
by the construction of such extensive systematic works, we
must allow that these ancient people had reached the earlier
stages of a civilisation of which no traces existed among the
savage tribes who alone occupied the country when first
visited by Europeans.

The animal mounds are of comparatively less importance
for our present purpose, as they imply a somewhat lower
grade of advancement; but the sepulchral and sacrificial

vii THE ANTIQUITY AND ORIGIN OF MAN 427

mounds exist in vast numbers, and their partial exploration
has yielded a quantity of articles and works of art which
throw some further light on the peculiarities of this mysteri-
ous people. Most of these mounds contain a large concave
hearth or basin of burnt clay, of perfectly symmetrical form,
on which are found deposited more or less abundant relics,
all bearing traces of the action of fire. We are therefore only
acquainted with such articles as are practically fire-proof, or
have accidentally escaped combustion. These consist of bone
and copper implements and ornaments, disks and tubes ;
pearl, shell, and silver beads, more or less injured by the fire ;
ornaments cut in mica; ornamental pottery; and numbers
of elaborate carvings in stone, mostly forming pipes for
smoking. l The metallic articles are all formed by hammer-
ing, but the execution is very good; plates of mica are
found cut into scrolls and circles ; the pottery, of which
very few remains have been found, is far superior to that
of any of the Indian tribes, since Dr. Wilson is of opinion
that it must have been formed on a wheel, as it is often of
uniform thickness throughout (sometimes not more than one-
sixth of an inch), polished, and ornamented with scrolls and
figures of birds and flowers in delicate relief. But the most
instructive objects are the sculptured stone pipes, representing
not only various easily recognisable animals, but also human
heads, so well executed that they appear to be portraits.
Among the animals, not only are such native forms as the
panther, bear, otter, wolf, beaver, raccoon, heron, crow, turtle,
frog, rattlesnake, and many others well represented, but also
the manatee, which perhaps then ascended the Mississippi as
it now does the Amazon, and the toucan, which could hardly
have been obtained nearer than Mexico. ^ The sculptured
heads are especially remarkable, because they present to us
the features of an intellectual and civilised people. The nose
in some is perfectly straight, and neither prominent nor
dilated ; the mouth is small, and the lips thin ; the chin and
upper lip are short, contrasting with the ponderous jaw of
the modern Indian, while the cheek-bones present no marked

1 Woven cloth, apparently of flax or hemp, as well as gauges supposed to
have been used to regulate the thickness of the thread, have also been found
in several of the mounds of Ohio (Foster's Prehistoric Races of the United
States, 1873, pp. 225-229).

TROPICAL NATURE

prominence. Other examples have the nose somewhat pro-
jecting at the apex in a manner quite unlike the features of
any American indigenes ; and although there are some which
show a much coarser face, it is very difficult to see in any of
them that close resemblance to the Indian type which these
sculptures have been said to exhibit. The few authentic
crania from the mounds present corresponding features, being
far more symmetrical and better developed in the frontal
region than those of any American tribes, although somewhat
resembling them in the occipital outline;1 while one was
described by its discoverer (Mr. W. Marshall Anderson) as a
" beautiful skull, worthy of a Greek."

The antiquity of this remarkable race may perhaps not
be very great as compared with the prehistoric man of Europe,
although the opinion of some writers on the subject seems
affected by that " parsimony of time " on which the late Sir
Charles Lyell so often dilated. The mounds are all over-
grown with dense forest, and one of the large trees was
estimated to be 800 years old, while other observers consider
the forest growth to indicate an age of at least 1000 years.
But it is well known that it requires several generations of
trees to pass away before the growth on a deserted clearing
comes to correspond with that of the surrounding virgin
forest, while this forest, once established, may go on growing
for an unknown number of thousands of years. The 800 or
1000 years estimate from the growth of existing vegetation
is a minimum which has no bearing whatever on the actual
age of these mounds ; and we might almost as well attempt
to determine the time of the glacial epoch from the age of
the pines or oaks which now grow on the moraines.

The important thing for us, however, is that when North
America was first settled by Europeans, the Indian tribes
inhabiting it had no knowledge or tradition of any preceding
race of higher civilisation than themselves. Yet we find that
such a race existed — that they must have been populous and
have lived under some established government ; while there
are signs that they practised agriculture largely, as, indeed,
they must have done to have supported a population capable
of executing such gigantic works in such vast profusion ; for
1 Wilson's Prehistoric Man, 3d ed., vol. ii. pp. 123-130.

vii THE ANTIQUITY AND ORIGIN OF MAN 429

it is stated that the mounds and earthworks of various kinds
in the State of Ohio alone amount to between eleven and
twelve thousand. In their habits, customs, religion, and arts,
they differed strikingly from all the Indian tribes; while
their love of art and of geometric forms, and their capacity
for executing the latter upon so gigantic a scale, render it
probable that they were a really civilised people, although the
form their civilisation took may have been very different from
that of later peoples, subject to very different influences and
the inheritors of a longer series of ancestral civilisations.
We have here, at all events, a striking example of the transi-
tion, over an extensive country, from comparative civilisation
to comparative barbarism, the former leaving no tradition and
hardly any trace of its influence on the latter.

As Mr. Mott well remarks : " Nothing can be more striking
than the fact that Easter island and North America both give
the same testimony as to the origin of the savage life lound
in them, although in all circumstances and surroundings the
two cases are so different. If no stone monuments had been
constructed in Easter island, or mounds containing a few
relics saved from fire, in the United States, we might never have
suspected the existence of these ancient peoples." He argues,
therefore, that it is very easy for the records of an ancient
nation's life entirely to perish or to be hidden from observa-
tion. Even the arts of Nineveh and Babylon were unknown
only a generation ago, and we have only just discovered the
facts about the mound-builders of North America.

But other parts of the American continent exhibit parallel
phenomena. Eecent investigations show that in Mexico,
Central America, and Peru, the existing race of Indians has
been preceded by a distinct and more civilised race. This
is proved by the sculptures of the ruined cities of Central
America, by the more ancient terra-cottas and paintings of
Mexico, and by the oldest portrait -pottery of Peru. All
alike show markedly non- Indian features, while they often
closely resemble modern European types. Ancient crania,
too, have been found in all these countries, presenting very
different characters from those of any of the existing indi-
genous races of America.1

1 Wilson's Prehistoric Man, 3d ed., vol. ii. pp. 125, 144.

430 . TROPICAL NATURE

The

There is one other striking example of a higher phase of
development in science and the arts being succeeded by a
lower phase, which is in danger of being forgotten because it
has been made the foundation of theories which seem wild
and fantastic, and are probably in great part erroneous. I
allude to the Great Pyramid of Egypt, whose form, dimen-
sions, structure, and uses have recently been the subject of
elaborate works by Professor Piazzi Smyth. Now the admitted
facts about the pyramid are so interesting and so apposite to
the subject we are considering, that I beg to recall them to
your attention. Most of you are aware that this pyramid
has been carefully explored and measured by successive
Egyptologists, and that the dimensions have lately become
capable of more accurate determination owing to the discovery
of some of the original casing-stones, and the clearing away
of the earth from the corners of the foundation, showing the
sockets in which the corner-stones fitted. Professor Smyth
devoted many months of work with the best instruments, in
order to fix the dimensions and angles of all accessible parts
of the structure : and he has carefully determined -these by a
comparison of his own and all previous measures, the best
of which agree pretty closely with each other. The results
arrived at are —

1. That the pyramid is truly square, the sides being equal
and the angles right angles.

2. That the four sockets on which the four first stones of
the corners rested are truly on the same level.

3. That the directions of the sides are accurately to the
four cardinal points.

4. That the vertical height of the pyramid bears the same
proportion to its circumference at the base as the radius of a
circle does to its circumference.

Now all these measures, angles, and levels are accurate,
not as an ordinary surveyor or builder could make them, but
to such a degree as requires the very best modern instruments
and all the refinements of geodetical science to discover any
error at all. In addition to this we have the wonderful per-
fection of the workmanship in the interior of the pyramid,

vn THE ANTIQUITY AND ORIGIN OF MAN 431

the passages and chambers being lined with huge blocks of
stones fitted with the utmost accuracy, while every part of
the building exhibits the highest structural science.

In all these respects this largest pyramid surpasses every
other in Egypt. Yet it is universally admitted to be the
oldest, and also the oldest historical building in the world.

Now these admitted facts about the Great Pyramid are
surely remarkable and worthy of the deepest consideration.
They are facts which, in the pregnant words of the late Sir
John Herschel, "according to received theories ought not
to happen," and which, he tells us, should therefore be kept
ever present to our minds, since " they belong to the class of
facts which serve as the clue to new discoveries." According
to modern theories, the higher civilisation is ever a growth
and an outcome from a preceding lower state ; and it is
inferred that this progress is visible to us throughout all
history and in all material records of human intellect. But
here we have a building which marks the very dawn of
history, which is the oldest authentic monument of man's
genius and skill, and which, instead of being far inferior, is
very much superior to all which followed it. Great men are
the products of their age and country, and the designer and
constructors of this wonderful monument could never have
arisen among an unintellectual and half -barbarous people.
So perfect a work implies many preceding less perfect works
which have disappeared. It marks the culminating point of
an ancient civilisation, of the early stages of which we have
no trace or record whatever.

Conclusion

The three cases to which I have now adverted (and there
are many others) seem to require for their satisfactory inter-
pretation a somewhat different view of human progress from
that which is now generally accepted. Taken in connection
with the great intellectual power of the ancient Greeks —
which Mr. Galton believes to have been far above that of the
average of any modern nation — and the elevation, at once
intellectual and moral, displayed in the writings of Confucius,
Zoroaster, and the Vedas, they point to the conclusion that,
while in material progress there has been a tolerably steady

432 TROPICAL NATURE

advance, man's intellectual and moral development reached
almost its highest level in a very remote past. The lower,
the more animal, but often the more energetic types have,
however, always been far the more numerous ; hence such
established societies as have here and there arisen under the
guidance of higher minds have always been liable to be swept
away by the incursions of barbarians. Thus in almost every
part of the globe there may have been a long succession of
partial civilisations, each in turn succeeded by a period of
barbarism ; and this view seems supported by the occurrence
of degraded types of skull along with such " as might have
belonged to a philosopher," at a time when the mammoth and
the reindeer inhabited southern France.

Nor need we fear that there is not time enough for the
rise and decay of so many successive civilisations as this view
would imply, for the opinion is now gaining ground among
geologists that palaeolithic man was really preglacial, and that
the great gap (marked alike by a change of physical condi-
tions and of animal life) which in Europe always separates
him from his neolithic successor, was caused by the coming
on and passing away of the great ice age.

If the views now advanced are correct, many, perhaps
most, of our existing savages are the successors of higher
races ; and their arts, often showing a wonderful similarity in
distant continents, may have been derived from a common
source among more civilised peoples.

VIII

THE ANTIQUITY OF MAN IN NORTH AMERICA1

Ancient Shell Mounds— Man Coeval with Extinct Mammalia — Man in the
Glacial Period— Palaeolithic Implements in North America— The
Auriferous Gravels of California —Fossil Remains under the Ancient
Lava Beds — Works of Art in the Auriferous Gravels — Human Re-
mains in the Auriferous Gravels — Concluding Remarks on the
Antiquity of Man.

OVER a considerable portion of the northern hemisphere the
remains of man, or his works, have been found in association
with bones of the extinct mammalia which characterised the
Glacial epoch, and no evidence has been obtained that man
at that time differed more from modern savages than they
do among themselves. The facts which prove this antiquity
were, when first put forth, doubted, neglected, or violently
opposed, and it is now admitted that such opposition was
due to prejudice alone, and in every case led to the rejection
of important scientific truths. Yet after nearly thirty years'
experience we find that an exactly similar prejudice prevails,
even among geologists, against all evidence which carries man
one little step farther back into pre-Glacial or Pliocene times,
although if there is any truth whatever in the doctrine of
evolution as applied to man, and if we are not to adopt the
exploded idea that the Palaeolithic men were specially created
just when the flood of ice was passing away, they must have
had ancestors who must have existed in the Pliocene period,
if not earlier. Is it then so improbable that some trace of
man should be discovered at this period, that each particle of
evidence as it arises must be attacked with all the weapons of
1 This article appeared in the Nineteenth Century, Nov. 1887.
2F

434 TROPICAL NATURE

doubt, accusation, and ridicule, which for so many years
crushed down the truth with regard to Palaeolithic man?
One would think, as Jeremy Bentham said of another matter,
that it was " wicked or else unwise " to accept any evidence
for facts which are yet so inherently probable that the entire
absence of evidence for their existence ought to be felt to be
the greatest stumbling-block.

No better illustration of this curious prejudice can be
given than the way in which some recent discoveries of stone
implements in deposits of considerable antiquity in India are
dealt with. These implements are of quartzite, and are of
undoubtedly human workmanship. They were found in the
Lower Laterite formation, which is said to have undergone
great denudation and to be undoubtedly very ancient. Old
stone circles of a great but unknown antiquity are formed of
it. It is also stated that the distinction between the Tertiary
and post -Tertiary is very difficult in India, and the age of
these Laterite beds cannot be determined either by fossils,
which are absent, or by superposition. Yet we are informed,
" The presence of Palaeolithic implements proves that the rock
is of post-Tertiary origin." l Here we have the origin of man
taken as fixed and certain, so certain that his remains may be
used to prove the age of a doubtful deposit ! Nor do these
indications of great antiquity stand alone, for in the Ner-
budda fluviatile deposits Mr. Hackel has found stone weapons
in situ along with eleven species of extinct fossil mammalia.

Believing myself that the existence of man in the Tertiary
epoch is a certainty, and the discovery of his remains or works
in deposits of that age to be decidedly probable, I hold it to be
both wise and scientific to accept all evidence of his existence
before the Glacial epoch which would be held satisfactory for
a later period, and when there is any little doubt, to give the
benefit of the doubt in favour of the find rather than against
it. I hold further that it is equally sound doctrine to give
some weight to cumulative evidence ; since, when a thing is
not improbable in itself, it surely adds much to the argument
in its favour that facts which tend to prove it come from
many different and independent sources — from those who are
quite ignorant of the interest that attaches to their discovery,
1 Manual of the Geology of India, p. 370,

via THE ANTIQUITY OF MAN IN NORTH AMERICA 435

as well as from trained observers who are fully aware of the
importance of every additional fact and the weight of each
fresh scrap of evidence. Having by the kindness of Major
Powell, the able Director of the United States Geological Sur-
vey, been able to look into the evidence recently obtained
bearing on this question in the North American continent, I
believe that a condensed account of it will certainly prove of
interest to English readers.

The most certain tests of great antiquity, even though they
afford us no accurate scale of measurement, are furnished by
such natural changes as we know occur very slowly. Changes
in the distribution of animals or plants, modifications of the
earth's surface, the extinction of some species and the intro-
duction of others, are of this nature, and they are the more
valuable because during the entire historical period changes
of this character are either totally unknown or of very small
amount. Let us then see what changes of this kind have
occurred since man inhabited the North American continent.

Ancient Shell Mounds

The shell heaps of the Damariscotta River, in Maine, are re-
markable for their number and extent. The largest of these
stretches for about half a mile along the shore, and is often six
or seven feet, and in one place twenty-five feet, in thickness.
They consist almost exclusively of oyster shells of remarkable
size, frequently having a length of eight or ten inches, and some-
times reaching twelve or fourteen inches. They contain frag-
ments of bones of edible animals, charcoal, bone implements, and
some fragments of pottery. The surface is covered to a depth
of several inches with vegetable mould, and large trees grow on
them, some more than a century old. The special feature to
which we now call attention is "that at the present time
oysters are only found in very small numbers, too small to
make it an object to gather them ; and we were credibly in-
formed that they have not been found in larger quantities
since the settlement in the neighbourhood. It cannot be sup-
posed that the immense accumulations now seen on the shores
of Salt Bay could have been made unless oysters had existed
in very large numbers in the adjoining waters." x Here we
1 Second Annual Report of Trustees of Peabody Museum, p. 18.

TROPICAL NATURE

have evidence of an important change in the distribution of a
species of mollusc since the banks were formed.

On the St. John's river, Florida, are enormous heaps
largely composed of two freshwater shells, Ampullaria de-
pressa andPaludina multilineata, which cover acres of ground,
and are often six or eight feet thick. Professor Wyman,
who explored these heaps, remarks : "It seems incredible to
one who searches the waters of the St. John's and its lakes at
the present time, that the two small species of shells above
mentioned could have been obtained in such vast quantities
as are seen brought together in these mounds, unless at the
times of their formation the shells existed more abundantly
than now, or the collection of them extended through very
long periods of time. When it is borne in mind that the
shell heaps afford the only suitable surface for dwellings,
being most commonly built in swamps, or on lands liable to
be annually overflowed by the rise of the river, they appear
to be necessarily the result of the labours of a few living on
a limited area at one time. At present it would be a very
difficult matter to bring together in a single day enough of
these shells for the daily meals of an ordinary family." l

On the Lower Mississippi, at Grand Lake, are shell banks
of great extent which are now fifteen miles inland ; while Nott
and Gliddon describe similar banks on the Alabama River fifty
miles inland, and they believe that Mobile Bay must have
extended so far at the time the shells were collected. These
beds are often covered with vegetable mould from one to two
feet thick, and on this grow large forest trees. Equally indica-
tive of long occupation and great antiquity is the enormous
shell mound at San Pablo, on the bay of San Francisco, which
is nearly a mile long and half a mile wide, and more than
twenty feet thick. Numerous Indian skeletons and mummies
have been found in it, showing that it had been subsequently
used as a place of burial. Some mounds in Florida have
growing on them enormous live oaks from thirteen to twenty-
six feet in circumference at five feet from the ground, some
of which are estimated to be about 600 years old, indicating
the minimum age possible for the heaps, but not necessarily
approaching to their real age.

1 Fifth Annual Report of Pedbody Museum, p. 22.

vni THE ANTIQUITY OF MAN IN NORTH AMERICA 437

The extensive shell heaps of the Aleutian islands have
been carefully examined and reported on by Mr. Dall, and are
found to exhibit some remarkable and probably unique pecu-
liarities. Complete sections were made across several of these,
and they were found to consist of a series of distinct layers,
each marked by some well-defined characteristics. In the
upper layers only are there any mammalian remains, and
these may be divided into three subdivisions. In the upper
bed there are found seals, walruses, etc., aquatic and land
birds, the arctic fox and dog, with well-made weapons and
implements, awls, whetstones, needles, and lamps. In the
next layer the dog and fox are absent, as are remains of
large whales ; and in the lower mammalian layer there are
seals and small cetacea only, but no birds or land animals,
and the weapons found are ruder. We then come to a con-
siderable layer in which there are no mammalian remains
whatever, but only fish-bones and molluscan shells, with rude
knives, lance heads, etc. Below this is a bottom deposit con-
sisting entirely of the shells of echini, and containing no
weapons, tools, or implements of any kind, except towards
the surface of the layer, where a few hammer stones are
found, round pebbles with an indentation on each side for
the finger and thumb. Echinus' eggs are now eaten raw by
the Aleuts, and it is the only eatable part of the animal. It
takes forty or fifty full-sized echini for a meal. Some of the
heaps cover five acres, and from a careful estimate founded
on experiments, and taking the probable numbers of a colony
which could have lived on such a spot, Mr. Dall calculates
that it would take about 2200 years to form such an accu-
mulation. A similar estimate applied to the upper layers
brings the time required for the accumulation of the entire
series to 3000 years, but that is on the supposition that they
were formed continuously. This, however, was evidently not
the case. Each layer indicates a change of inhabitants with
different habits and in a somewhat different phase of civilisa-
tion, and each such change may imply the lapse of a long
period, during which the site was abandoned and no accumu-
lation went on. These shell heaps may, therefore, carry us
back to a very remote antiquity.

438 TROPICAL NATURE

Man Coeval with Extinct Mammalia

We next come to remains of man or his works found in
association with the bones of extinct mammalia. The great
mastodon skeleton in the British Museum found by Dr. Koch
in the Osage valley, Missouri, had stone arrow-heads and
charcoal found near it, but the fact was at the time received
with the same incredulity as all other evidences of the anti-
quity of man. This animal was found at a depth of twenty
feet, under seven alternate layers of loam, gravel, clay, and
peat, with a forest of old trees on the surface, and one of the
arrow-heads lay under the thigh-bone of the mastodon and
in contact with it. About the same date (1859) Dr. Holmes
communicated to the Philadelphia Academy of Natural
Sciences his discovery of fragments of pottery in connection
with bones of the mastodon and megatherium on the Ashley
river of South Carolina.

Such cases as these remove all improbability from the
celebrated Natchez man, a portion of a human pelvis from
the loess of the Mississippi, which contains bones of the
mastodon, megalonyx, horse, bison, and other extinct animals.
This bone was stated by Sir Charles Lyell " to be quite in
the same state of preservation and of the same black colour
as the other fossils." Dr. Joseph Leidy agrees with this
statement, yet he and Professor C. G. Forshey maintain that
it is "more probable" that the human bone fell down the
cliff from some Indian grave near the surface. Sir Charles
Lyell well remarks that " had the bone belonged to any other
recent mammal, such a theory would never have been resorted
to." The admitted identity of the state of preservation and
appearance of the human and animal bones is certainly not
consistent with the view that the one is recent, the other
ancient ; the one artificially buried near the surface, the other
in a natural deposit thirty feet below the surface.

Of a similar character to the above is the basket-work mat
found in a rock-salt deposit fifteen to twenty feet below the
surface in Petit Anse island, Louisiana, two feet above which
were fragments of tusks and bones of an elephant. The salt
is said to be very pure, extending over an area of 5000 acres,
and the formation of such a deposit requires a considerable

viii THE ANTIQUITY OF MAN IN NORTH AMERICA 439

change of physical conditions from those now existing, and
thus of itself implies great antiquity.1

These indications of the great antiquity of American man
are now supported by such a mass of evidence of the same
character that all the improbability supposed at first to
attach to them has been altogether removed. As an illustra-
tion of this evidence I need only refer here to the Eeport
on the Loess of Nebraska, by an experienced geologist, Dr.
Samuel Aughey, who states that this deposit, which is now
believed by the best American geologists to be of Glacial
origin, and which covers enormous areas, contains throughout
its entire extent many remains of mastodons and elephants,
and that he himself had found an arrow and a spear-head of
flint at depths of fifteen and twenty feet in the deposit. One
of these was thirteen feet below a lumbar vertebra of Elephas
americanus.

Man in the Glacial Period

We now take a decided step backwards in time, to relics
of human industry within or at the close of the Glacial period
itself. About twenty years ago a well was sunk through the
drift at Games, a few miles south of Lake Ontario, and at a
depth of seventeen feet there were found lying on the solid
rock three large stones enclosing a space within which were
about a dozen charred sticks, thus closely resembling the cook-
ing fires usually made by savages. Mr. G. K. Gilbert, of the
U.S. Geological Survey, obtained the information from the
intelligent farmer who himself found it, and after a close ex-
amination of the locality and the drift deposit in its relation
to the adjacent lakes, comes to the conclusion that the hearth
must have been used "near the end of the second Glacial
period," and at the time of the separation of Lake Ontario
from Lake Erie. When Mr. Gilbert gave an account of his
researches on this matter at the meeting of the Washington
Anthropological Society, 16th November 1886, two other
gentlemen reported finds of similar character. Mr. Murdock,
of the Point Barrow Station, near the extreme north-west
corner of the continent, in making an excavation for an earth
thermometer, found an Eskimo snow-goggle beneath more
1 Foster's Prehistoric Races of tlie United States, p. 56.

440 TROPICAL NATURE

than twenty feet of frozen gravel and earth capped by a foot
of turf. This being near the shores of the Arctic Sea may
be a comparatively recent beach -formation and of no very
great antiquity ; but the remaining discovery was more im-
portant. Mr. W. J. M'Gee, a gentleman who has specially
studied the Glacial and post-Glacial formations for the U.S.
Geological Survey, described the finding by himself of a spear-
head in the quaternary deposits of the Walker River Canon,
Nevada. These beds consist of several feet of silt and loose
material at the top, then a layer of calcareous tufa lying upon
twenty to thirty feet of white marl, containing remains of
extinct mammalia, and resting unconformably upon somewhat
similar beds of earlier date. The spear-head was found with
its point just projecting from the face of the marl about
twenty-six feet below the surface. Before removing the im-
plement, he carefully studied the whole surroundings, and
finally came to the conclusion that it had been embedded in
the marl during its formation. The beds were deposited by
the ancient Lake Lahonton. They have been thoroughly in-
vestigated by able geologists, and have been referred to the
close of the Glacial period, or about the same time as the
hearth described by Mr. Gilbert. The spear -head is three
and a half inches in length, finely made, and well preserved.

About a hundred miles north-west of St. Paul, in Central
Minnesota, a thin deposit has been discovered containing
numerous quartzite implements. They occur at a depth of
from twelve to fifteen feet in an old river terrace of modified
drift, and the deposit marks an ancient land surface on which
the implements are found, and which must have been de-
posited at about the close of the last Glacial epoch.1 Mr. N.
H. Winchell, State geologist of Minnesota, has found similar
chips and implements in the upper part of the same deposit ;
and also human bones in the eastern terrace bluffs at Minne-
apolis, in a formation of about the same age as the above.

The same writer reports a still more remarkable discovery
of a fragment of a human lower jaw in the red clay and
boulder drift, but resting immediately on the limestone rock.
This red clay belongs to the first or oldest Glacial period, and

1 "Vestiges of Glacial Man in Minnesota," by F. E. Babbitt, Proc. of Am.
Assoc., vol. xxxii. 1883.

vin THE ANTIQUITY OF MAN IN NORTH AMERICA 441

we thus have the proofs of man's existence carried back not
only to the end of the Glacial epoch, but perhaps to its very
commencement. l

Palceolithic Implements in North America
We now come to the very interesting discoveries of Dr.
Charles C. Abbott, of Trenton, New Jersey. In the ex-
tensive deposits of gravel in the valley of the Delaware, fresh
surfaces of which are continually exposed in the cliffs on the
river's banks, he has found large numbers of rude stone im-
plements, almost identical in size and general form with the
well-known palaeolithic implements of the valley of the Somme.
These have been found at depths of from five to over twenty
feet from the surface, in perfectly undisturbed soil, and that
they are characteristic of this particular deposit is shown by
the fact that they are found nowhere else in the same district.
Large boulders, some of very great size, are found throughout
the deposit, and in one case Dr. Abbott found a well-chipped
spear-shaped implement immediately beneath a stone weigh-
ing at least half a ton. Professor N. S. Shaler, of Cambridge,
Massachusetts, after examining the locality and himself ob-
taining some implements in situ, says, "I am disposed to
consider these deposits as formed in the sea near the foot of
the retreating ice-sheet when the sub-Glacial rivers were pour-
ing out the vast quantity of water and waste that clearly were
released during the breaking up of the great ice-time." Dr.
Abbott, however, adduces facts which seem to prove that
some part of the deposit at all events was sub-aerial, for he
states that the very large boulders often have immediately
under them a foot or more of soil between the lower surface
of the stone and the gravel, and that this layer often extends
some distance laterally, showing that it formed a land surface
on which the boulders rested, and which was subsequently
removed by water action, except where thus protected. At
any rate we may accept Professor Shaler's conclusion : " If
these remains are really those of man, they prove the exist-
ence of inter-Glacial man on this part of our shore." That
the implements are of human workmanship is quite certain,
and the fact stated by Professor Shaler himself, that " they
1 Annual Report of the State Geologist of Minnesota, 1877, p. 60.

442 TROPICAL NATURE

are made of a curious granular argillite, the like of which I
do not know in the place," is an additional proof of it. The
further fact that the remains of man himself have been dis-
covered in the same deposit completes the demonstration.
First a human cranium was found of peculiar characteristics,
being small, long, and very thick ; then a tooth ; and, lastly,
a portion of a human under jaw, found at a depth of sixteen
feet from the surface, near where a fragment of mastodon
tusk had been found some years before. In recording this
last discovery the curator of the Peabody Museum remarks :
" To Dr. Abbott alone belongs the credit of having worked
out the problem of the antiquity of man on the Atlantic coast,"
so that this gentleman appears to stand in a somewhat similar
relation to this great question in America as did Boucher de
Perthes in Europe. His researches are recorded in the first,
second, and third volumes of the Eeports of the Peabody
Museum.

The interesting series of researches now briefly recorded
has led us on step by step through the several stages of the
quaternary at least as far back as the first great Glacial
period, thus corresponding to the various epochs of Neolithic
and Palaeolithic man in Europe, terminating in the Suffolk
flints, claimed to be pre- Glacial by Mr. Skertchley, or the
earliest traces of human occupancy in Kent's Cavern, of
which Mr. Pengelly states that " he is compelled to believe
that the earliest men of Kent's Hole were inter-Glacial if not
pre-Glacial." It now remains to adduce the evidence which
carries us much farther back, and demonstrates the existence
of man in Pliocene times. This evidence is derived from the
works of art and human crania found in the auriferous gravels
of California, and in order to appreciate duly its weight and
importance, it is necessary to understand something of the
physical characteristics of the country and the nature of the
gravels themselves, with their included fossils, since both
these factors combine to determine their geological age.

The Auriferous Gravels of California

The great lateral valleys of the Sierra Nevada are charac-
terised by enormous beds of gravel, sometimes in thick de-
posits on the sides or filling up the whole bed of the valley,

via THE ANTIQUITY OF MAN IN NORTH AMERICA 443

at other times forming detached hills or even mountains of
considerable size. These gravel deposits are often covered
with a bed of hard basalt or lava, having a generally level
but very rugged surface, and hence possessing, when isolated,
a very peculiar form, to which the name " table mountain "
is often given. These tabular hills are sometimes 1000 or
even 1500 feet high, and the basaltic capping varies from fifty
to 200 feet thick. The gravels themselves are frequently
interstratified with a fine white clay and sometimes with
layers of basalt.

Geological exploration of the district clearly exhibits the
origin of this peculiar conformation of the surface. At some
remote period the lower lateral valleys of the Sierra Nevada
became gradually filled with deposits of gravel brought down
from the higher and steeper valleys. During the time this
was going on there were numerous volcanic eruptions in the
higher parts of the range, sending out great showers of ashes,
which formed the beds now consolidated into pipe-clay or
cement, while occasional lava streams produced intercalating
layers of basalt. After this had gone on for a long period,
and the valleys had in many places been filled up with debris
to the depth of many hundred feet, there was a final and very
violent eruption, causing outflows of lava, which ran down
many of the valleys, filled the river beds, and covered up a
considerable portion of the gravel deposits. These lava
streams, some of which may be now traced for a length of
twenty miles, of course flowed down the lower or middle
portion of each valley, so that any part of the gravel remain-
ing uncovered would be that most remote from the river bed
towards one or other side of the valley. This gravel, being
now the lowest ground as well as that most easily denuded,
would of course be eaten away by the torrents and mark the
commencement of new river beds, which thenceforth went
on deepening their channels and forming new valleys which
undermined and carried away some of the gravel, but always
left steep slopes and cliffs wherever the lava flow protected
the surface from the action of the rains. Hence it happens
that the existing rivers are often in very different directions
from the old ones, and sometimes cut across them, and thus
isolated table mountains have been left rising up out of the

444 TROPICAL NATURE

surrounding plain or valley. What was once a single lava
stream now forms several detached hills, the tops of which
can be seen to form parts of one gently inclined plane, the
surface of the original lava flow, now 1000 feet or more
above the adjacent valleys. The American and Yuba valleys
have been lowered from 800 to 1500 feet, while the Stanis-
laus river gorge has cut through one of these basalt-covered
hills to the depth of 1500 feet.

While travelling by stage, in the summer of 1887, from
Stockton to the Yosemite valley, I passed through this very
district, and was greatly impressed by the indications of
vast change in the surface of the country since the streams of
lava flowed down the valleys. In the Stanislaus valley the
numerous " table mountains " were very picturesque, often
running out into castellated headlands or exhibiting long
ranges of rugged black cliffs. At one spot the road passed
through the ancient river-bed, clearly marked by its gravel,
pebbles, and sand, but now about three or four hundred feet
above the present river. We also often saw rock surfaces of
metamorphic slates far above the present river-bed, thus
proving that the original bed-rocks of the valley, as well as the
lava and gravels, have been cut away to a considerable depth
since the epoch of the lava flows. The ranges of " table
mountains," now separated by deep valleys more than 1000
feet below them, could easily be seen, by their perfect agree-
ment of slope and level, to have once formed part of an
enormous lava stream spread over a continuous surface of
gravel and rock

Fossil Remains under the Ancient Lava Beds
These great changes in the physical conditions and in the
surface features of the country alone imply a great lapse of
time, but they are enforced and rendered even more apparent
by the proofs of change in the flora and fauna afforded by the
fossils, which occur in some abundance both in the gravels and
volcanic clays. The animal remains found beneath the basaltic
cap are very numerous, and are all of extinct species. They
belong to the genera rhinoceros, elotherium, felis, canis, bos,
tapirus, hipparion, equus, elephas, mastodon, and auchenia, and
form an assemblage entirely distinct from those that now

vin THE ANTIQUITY OF MAN IN NORTH AMERICA 445

inhabit any part of the North American continent. Besides
these we have a tolerably abundant series of vegetable remains,
well preserved in the white clays formed from the volcanic
ash. These comprise forty-nine species of deciduous trees and
shrubs, all distinct from those now living, while not a single
coniferous leaf or fruit has been found, although pines and firs
are now the prevalent trees all over the sierra. Professor
Lesquereaux, who has described these plants, considers them
to be of Pliocene age with some affinities to Miocene ; while
Professor Whitney, the State geologist of California, considers
that the animal remains indicate at least a similar antiquity.

These abundant animal and vegetable remains have mostly
been discovered in the process of gold-mining, the gravel and
sand of the old river-beds preserved under the various flows
of basalt being especially rich in gold. Numerous shafts have
been sunk and underground tunnels excavated in the auriferous
gravels and clays, and the result has been the discovery not
only of extinct animals and plants, but of works of art and
human remains. The former have been found in nine different
counties in the same gravels in which the extinct animals
occur, while in no less than five widely separate localities,
underneath the ancient lava flows, remains of man himself
have been discovered. In order to show the amount of this
evidence, and to enable us to appreciate the force or weakness
of the objections with which, as usual, it has been received, a
brief enumeration of these discoveries will be made. We will
begin with the works of art as being the most numerous.

Works of Art in the Auriferous Gravels
In Tuolumne County from 1862 to 1865 stone mortars
and platters were found in the auriferous gravel along with
bones and teeth of mastodon ninety feet below the surface,
and a stone muller was obtained in a tunnel driven under
Table Mountain. In 1870 a stone mortar was found at a
depth of sixty feet in gravel under clay and " cement," as the
hard clay with vegetable remains (the old volcanic ash) is
called by the miners. In Calaveras County from 1860 to
1869 many mortars and other stone implements were found
in the gravels under lava beds, and in other auriferous gravels
and clays at a depth of 150 feet. In Amador County stone

446 TROPICAL NATURE

mortars have been found in similar gravel at a depth of forty
feet. In Placer County stone platters and dishes have been
found in auriferous gravels from ten to twenty feet below the
surface. In Nevada County stone mortars and ground discs
have been found from fifteen to thirty feet deep in the gravel.
In Butte County similar mortars and pestles have been found
in the lower gravel beneath lava beds and auriferous gravel ;
and many other similar finds have been recorded. It must
be noted that the objects found are almost characteristic of
California, where they are very abundant in graves or on the
sites of old settlements, having been used to pound up acorns,
which formed an important part of the food of the Indians.
They occur literally by hundreds, and are so common that
they have little value. It seems therefore absurd to suppose
that in scores of cases, over a wide area of country and over
a long series of years, gold -miners should have taken the
trouble to carry down into their mines or mix with their
refuse gravel these articles, of whose special scientific interest
in the places where found they have no knowledge whatever.
It is further noted that many of these utensils found in the
old gravels are coarse and rudely finished as compared with
those of more recent manufacture found on the surface. The
further objection has been made that there is too great a
similarity between these objects and those made in com-
paratively recent times. But the same may be said of the
most ancient arrow and spear heads and those made by
modern Indians. The use of the articles has in both cases
been continuous, and the objects themselves are so necessary
and so comparatively simple, that there is no room for any
great modification of form.

Human Remains in the Auriferous Gravels
We will now pass on to the remains of man himself. In
the year 1857 a fragment of a human skull with mastodon
debris was brought up from a shaft in Table Mountain,
Tuolumne County, from a depth of 180 feet below the surface.
The matter was investigated by Professor Whitney, the State
geologist, who was satisfied that the specimen had been found
in the " pay gravel," beneath a bed three feet thick of cement
with fossil leaves and branches, over which was seventy feet

viii THE ANTIQUITY OF MAN IN NORTH AMERICA 447

of clay and gravel. The most remarkable discovery, however,
is that known as the Calaveras skull. In the year 1866 some
miners found in the cement, in close proximity to a petrified
oak, a curious rounded mass of earthy and stony material
containing bones, which they put on one side, thinking it was
a curiosity of some kind. Professor Wyman, to whom it was
given, had great difficulty in removing the cemented gravel
and discovering that it was really a human skull nearly entire.
Its base was embedded in a conglomerate mass of ferruginous
earth, water-worn volcanic pebbles, calcareous tufa, and frag-
ments of bones, and several bones of the human foot and
other parts of the skeleton were found wedged into the
internal cavity of the skull. Chemical examination showed
the bones to be in a fossilised condition, the organic matter
and phosphate of lime being replaced by carbonate. It was
found beneath four beds of lava, and in the fourth bed of
gravel from the surface ; and Professor Whitney, who after-
wards secured the specimen for the State Geological Museum,
has no doubt whatever of its having been found as described.

In Professor Whitney's elaborate Eeport on the Auriferous
Gravels of the Sierra Nevada, from which most of the pre-
ceding sketch is taken, he arrives at the conclusion that
the whole evidence distinctly proves "that man existed in
California previous to the cessation of volcanic activity in the
Sierra Nevada, to the epoch of greatest extension of the
glaciers in that region, and to the erosion of the present river-
canons and valleys, at a time when the animal and vegetable
creations differed entirely from what they are now, and
when the topographical features of the State were extremely
unlike those exhibited by the present surface." He elsewhere
states that the animal and vegetable remains of these deposits
prove them to be of "at least as ancient a date as the
European Pliocene."

Professor Whitney enumerates two other cases in which
human bones have been discovered in the auriferous gravel,
and in one of them the bones were found by an educated
observer, Dr. Boyce, M.D., under a bed of basaltic lava eight
feet thick ; but these are of but little importance when com-
pared with the preceding cases, as to which we have such full
and precise details. The reason why these remarkable dis-

448 TROPICAL NATURE

coveries should have been made in California rather than in
any other part of America is sufficiently apparent if we consider
the enormous amount of excavation of the Pliocene gravels in
the long-continued prosecution of gold-mining, and also the
probability that the region was formerly, as now, characterised
by a milder climate, and a more luxuriant perennial vegetation,
and was thus able to support a comparatively dense popula-
tion even in those remote times. Admitting that man did
inhabit the Pacific slope at the time indicated, the remains
appear to be of such a character as might be anticipated, and
present all the characteristics of genuine discoveries.

Concluding Remarks on tJie Antiquity of Man
Even these Californian remains do not exhaust the proofs
of man's great antiquity in America, since we have the record
of another discovery which indicates that he may, possibly,
have existed at an even more remote epoch. Mr. E. L.
Berthoud has described the finding of stone implements of a
rude type in the Tertiary gravels of the Crow Creek, Colorado.
Some shells were obtained from the same gravels, which were
determined by Mr. T. A. Conrad to be species which are
" certainly not later than Older Pliocene, or possibly Miocene."
The account of this remarkable discovery, published in the
Proceedings of the Academy of Natural Sciences of Philadelphia,
1872, is not very clear or precise, and it is much to be wished
that some competent geologist would examine the locality.
But the series of proofs of the existence of man by the dis-
covery of his remains or his works going back step by step to
the Pliocene period, which have been now briefly enumerated,
takes away from this alleged discovery the extreme im-
probability which would be held to attach to it at the time
when it was made.

It is surely now time that this extreme scepticism as to
any extension of the human period beyond that reached by
Boucher de Perthes, half a century ago, should give way to
the ever -increasing body of facts on the other side of the
question. Geologists and anthropologists must alike feel that
there is a great, and at present inexplicable, chasm interven-
ing between the earliest remains of man and those of his
animal predecessors — that the entire absence of the " missing

vni THE ANTIQUITY OF MAN IN NORTH AMERICA 449

link " is a reproach to the doctrine of evolution ; yet with
strange inconsistency they refuse to accept evidence which in
the case of any extinct or living animal, other than man, would
be at least provisionally held to be sufficient, but follow in the
very footsteps of those who blindly refused even to examine
into the evidence adduced by the earlier discoverers of the
antiquity of man, and thus play into the hands of those who
can adduce his recent origin and unchangeability as an argu-
ment against the descent of man from the lower animals.
Believing that the whole bearing of the comparative anatomy
of man and of the anthropoid apes, together with the absence
of indications of any essential change in his structure during
the quaternary period, lead to the conclusion that he must
have existed, as man, in Pliocene times, and that the inter-
mediate forms connecting him with the higher apes probably
lived during the early Pliocene or the Miocene period, it is
urged that all such discoveries as those described in the
present article are in themselves probable and such as we have
a right to expect. If this be the case, the proper way to treat
evidence as to man's antiquity is to place it on record, and
admit it provisionally wherever it would be held adequate
in the case of other animals ; not, as is too often now the case,
ignore it as unworthy of acceptance or subject its discoverers
to indiscriminate accusations of being either impostors them-
selves or the victims of impostors. Error is sure to be soon
detected, and its very detection is often a valuable lesson.
But facts once rejected are apt to remain long buried in
obscurity, and their non-recognition may often act as a check
to further progress. It is in the hope of inducing a more
healthy public opinion on this interesting and scientifically
important question that this brief record of the evidences of
man's antiquity in North America has been compiled.

2a

IX

THE DEBT OF SCIENCE TO DARWIN1

The Century before Darwin — The Voyage of the Beagle — The Journal of
Researches — Studies of Domestic Animals — Studies of Cultivated and
Wild Plants — Researches on the Cowslip, Primrose, and Loosestrife
— The Struggle for Existence — Geographical Distribution and Dis-
persal of Organisms— The Descent of Man and Later Works— Estimate
of Darwin's Life- Work.

THE great man recently taken from, us had achieved an
amount of reputation and honour perhaps never before
accorded to a contemporary writer on science. His name
has given a new word to several languages, and his genius is
acknowledged wherever civilisation ex'tends. Yet .the very
greatness of his fame, together with the number, variety, and
scientific importance of his works, has caused him to be
altogether misapprehended by the bulk of the reading public.
Every book of Darwin's has been reviewed or noticed in
almost every newspaper and periodical, while his theories
have been the subject of so much criticism and so much
dispute, that most educated persons have been able to obtain
some general notion of his teachings, often without having
read a single chapter of his works, — and very few, indeed,
except professed students of science, have read the whole
series of them. It has been so easy to learn something of
the Darwinian theory at second-hand that few have cared
to study it as expounded by its author.

It thus happens that, while Darwin's name and fame are
more widely known than in the case of any other modern
man of science, the real character and importance of the
work he did are as widely misunderstood. The best scientific

1 This article appeared in the Century Magazine of January 1883.

ix THE DEBT OF SCIENCE TO DARWIN 451

authorities rank him far above the greatest names in natural
science — above Linnaeus and Cuvier, the great teachers of a
past generation — above De Candolle and Agassiz, Owen and
Huxley, in our own times. Many must feel inclined to ask, —
What is the secret of this lofty pre-eminence so freely accorded
to a contemporary by his fellow-workers ? What has Darwin
done, that even those who most strongly oppose his theories
rarely suggest that he is overrated ? Why is it universally felt
that the only name with which his can be compared in the
whole domain of science is that of the illustrious Newton ?

It will be my endeavour in the present chapter to answer
these questions, however imperfectly, by giving a connected
sketch of the work which Darwin did, the discoveries which
he made, the new fields of research which he opened up, the
new conceptions of nature which he has given us. Such a
sketch may help to clear away some of the obscurity which
undoubtedly prevails as to the cause and foundation of
Darwin's pre-eminence.

In order to understand the vast and fundamental change
effected by the publication of Darwin's most important
volume — The Origin of Species — we must take a hasty glance
at the progress of the science of natural history during the
preceding century.

The Century "before, Darwin

Almost exactly a hundred years before Darwin we find
Linnaeus and his numerous disciples hard at work describing
and naming all animals and plants then discovered, and
classifying them according to the artificial method of the
great master, which is still known as the Linnaean System ;
and from that time to the present day a large proportion of
naturalists are fully occupied with this labour of describing
new species and new genera, and in classifying them
according to the improved and more natural systems which
have been gradually introduced.

But another body of students have always been dis-
satisfied with this superficial mode of studying externals
only, and have devoted themselves to a minute examination
of the internal structure of animals and plants ; and early in
this century the great Cuvier showed how this knowledge of

452 TROPICAL NATURE

anatomy could be applied to the classification of animals
according to their whole organisation in a far more natural
manner than by the easier method of Linnaeus. Later on,
when improved microscopes and refined optical and chemical
tests became available, the study of anatomy was carried
beyond the knowledge of the parts and organs of the body —
such as bones, muscles, blood-vessels, and nerves — to the
investigation of the tissues, fibres, and cells of which these
are composed ; while the physiologists devoted themselves to
an inquiry into the mode of action of this complex machinery,
so as to discover the use of every part, the nature of its
functions in health and disease, and, as far as possible, the
nature of the forces which kept them all in action.

Down to the middle of the present century the study of
nature advanced with giant strides along these separate lines
of research, while the vastness and complexity of the subject
led to a constantly increasing specialisation and division of
labour among naturalists, the result being that each group of
inquirers came to look upon his own department as more or
less independent of all the others, each seemed to think that
any addition to his body of facts was an end in itself, and that
any bearing these facts might have on other branches of the
study or on the various speculations as to the "system of
nature " or the " true method of classification " that had at
various times been put forth was an altogether subordinate
and unimportant matter. And, in fact, they could hardly
think otherwise. For, while there was much talk of the
"unity of nature," a dogma pervaded the whole scientific
world which rendered hopeless any attempt to discover this
supposed unity amid the endless diversity of organic forms
and structures, while so much of it as might be detected
would necessarily be speculative and unfruitful. This dogma
was that of the original diversity and permanent stability of
species, a dogma which the rising generation of naturalists
must find it hard to believe was actually held, almost
universally, by the great men they look up to as masters in
their several departments, and held for the most part with
an unreasoning tenacity and scornful arrogance more suited
to politicians or theologians than to men of science. Although
the doctrine of the special and independent creation of every

ix THE DEBT OF SCIENCE TO DARWIN 453

species that now exists or ever has existed on the globe was
known to involve difficulties and contradictions of the most
serious nature, although it was seen that many of the facts
revealed by comparative anatomy, by embryology, by geo-
graphical distribution, and by geological succession were
utterly unmeaning and even misleading, in view of it; yet,
down to the period we have named, it may be fairly stated
that nine-tenths of the students of nature unhesitatingly
accepted it as literally true, while the other tenth, though
hesitating as to the actual independent creation, were none
the less decided in rejecting utterly and scornfully the views
elaborated by Lamarck, by Geoffroy St. Hilaire, and at a
much later date by the anonymous author of the Vestiges of
Creation — that every living thing had been produced by some
modification of ordinary generation from parents more or less
closely resembling it. Holding such views of the absolute
independence of each species, it almost necessarily followed
that the only aspect of nature of which we could hope to
acquire complete and satisfactory knowledge was that which
regarded the species itself. This we could describe in the
minutest detail ; we could determine its range in space and
in time; we could investigate its embryology from the
rudimental germ, or even from the primitive cell, up to the
perfect animal or plant ; we could learn every point in its
internal structure, and we might hope, by patient research
and experiment, to comprehend the use, function, and mode
of action of every tissue and fibre, and ultimately of each
cell and organic unit. All this was real knowledge, was solid
fact. But, so soon as we attempted to find out the relations
of distinct species to each other, we embarked on a sea of
speculation. We could, indeed, state how one species differed
from another species in every particular of which we had
knowledge ; but we could draw no sound inferences as to the
reason or cause of such differences or resemblances, except by
claiming to know the very object and meaning of the creator
in producing such diversity. And, in point of fact, the chief
inference that was drawn is now proved to be erroneous. It
was generally assumed, as almost self-evident, that the
ultimate cause of the differences in the forms, structures, and
habits of the organic productions of different countries, was

454 TROPICAL NATURE

that each species inhabiting a country was specially adapted
to the physical conditions that prevailed there, to which it
was exactly fitted. Even if this theory had been true, it was
an unproductive ultimate fact, for it was never pretended
that we could discover any reason for the limitation of
humming-birds and cactuses to America, of hippopotami to
Africa, or of kangaroos and gum-trees to Australia ; and we
were obliged to believe either that these countries possessed
hidden peculiarities of climate or other conditions, or that
this was only one out of many unknown and unknowable
causes determining the special action of the creative power.
All this was felt to be so unsatisfactory that the majority of
naturalists openly declared that their sole business was to
accumulate facts, and that any attempt to co-ordinate these
facts and see what inferences could be drawn from them was
altogether premature. In this frame of mind, year after
year passed away, adding its quota to the vast mass of
undigested facts which were accumulating in every branch of
the science. The remotest parts of the globe were ransacked
to add to the treasures of our museums, and the number of
known species became so enormous that students began to
confine themselves not merely to single classes, as birds or
insects, but to single orders, as beetles or land-shells, or even
to smaller groups, as weevils or butterflies. All, too, were
so impressed with the belief in the reality and permanence of
species, that endless labour was bestowed on the attempt to
distinguish them — a task whose hopelessness may be inferred
from the fact that, even in the well-known British flora, one
authority describes sixty-two species of brambles and roses,
another of equal eminence only ten species of the same
groups; and it is by no means uncommon for two, five, or
even ten species of one author to be classed as a single
species by another. All this time geologists had been so
assiduously at work in the discovery of organic remains that
the extinct species often equalled, and, in some groups —
as the Mollusca — very far exceeded, those now living on the
earth, and these were all found to belong to the very same
classes and orders as the living forms, and to form part of
one great system. Much attention was now paid to the
geological succession of the different groups of animals, which

ix THE DEBT OF SCIENCE TO DARWIN 455

were found to exhibit a progressive advancement from
ancient to recent times, while the breaks in the series
between each great geological formation were held to show
that the older forms of life had been destroyed, and were
replaced by a new creation of a more advanced organisation
suited to the altered conditions of the world.

And thus, perhaps, we might have gone on to this day,
ever accumulating fresh masses of fact, while each set of
workers became ever more and more occupied in their own
departments of study, and, for want of any intelligible theory
to connect and harmonise the whole, less and less able to
appreciate the labours of their colleagues, had not Charles
Darwin made his memorable voyage round the world, and
thenceforth devoted himself, as so many had done before him,
to a life of patient research in the domain of organic nature.
But how different was the object attained ! Others have
added greatly to our knowledge of details, or created a
reputation by some important work ; he has given us new
conceptions of the world of life, and a theory which is itself
a powerful instrument of research ; has shown us how to
combine into one consistent whole the facts accumulated
by all the separate classes of workers, and has thereby
revolutionised the whole study of nature. Let us endeavour
to see by what means he arrived at this vast result.

The Voyage of the BEAGLE

Passing by the ancestry and early life of Darwin, which
have been made known to the whole reading public by many
biographical notices and recently by the publication of his
Life and Letters, we may begin with the first event to which
we can distinctly trace his future greatness — his appointment
as naturalist to the Beagle, on the recommendation of his
friend and natural -history teacher, Professor Henslow, of
Cambridge University. It was in 1831, when Darwin, then
twenty-two years of age, had just taken his B.A. degree, that
he left England on his five years' voyage in the Southern
Hemisphere. It is probably to this circumstance that the
world owes the great revolution in our conception of the
organic world so well known as the Darwinian theory. The
opportunity of studying nature in new and strange lands;

456 TROPICAL NATURE

of comparing the productions of one country with those of
another ; of investigating the physical and biological relations
of islands and continents; of watching the struggle for
existence in regions where civilisation has not disturbed the
free action and reaction of the various groups of animals and
plants on each other ; and, what is perhaps more important
still, the ample leisure to ponder again and again on every
phase of the phenomena which presented themselves, free
from the attractions of society and the disturbing excitement
of daily association with contemporary men of science, —
these are the conditions most favourable to the formation of
habits of original thought, and the months and years which
at first sight appear intellectually wasted in the companion-
ship of uncivilised man, or in the solitary contemplation of
nature, are those in which the seed was sown which was
destined to produce in after years the mature fruit of great
philosophical conceptions. Let us then first glance over the
Journal of Researches, in which are recorded the main facts
and observations which struck the young traveller, and see
how far we can detect here the germs of those ideas and
problems to the working out of which he devoted a long and
laborious life.

The Journal of Researches

The question of the causes which have produced the dis-
tribution and the dispersal of organisms seems to have been
a constant subject of observation and meditation. At an
early period of the voyage he collected infusorial dust which
fell on the ship when at sea, and he notes the suggestive fact
that in similar dust collected on a vessel 300 miles from land
he found particles of stone above the thousandth of an inch
square, and remarks : " After this fact, one need not be sur-
prised at the diffusion of the far lighter and smaller sporules
of cryptogamic plants." He records many cases of insects
occurring far out at sea, on one occasion when the nearest
land was 370 miles distant. He paid special attention to the
insects and plants inhabiting the Keeling or Cocos, and other
recently formed coralline or volcanic islands ; the contrast of
these with the peculiar productions of the Galapagos evidently
impressed him profoundly ; while the remarkable facts pre-

ix THE DEBT OF SCIENCE TO DARWIN 457

sented by this latter group of islands brought out so clearly
and strongly the insuperable difficulties of the then accepted
theory of the independent origin of species, as to keep this
great problem ever present to his mind, and, at a later period,
led him to devote himself to the patient and laborious in-
quiries which were the foundation of his immortal work. He
again and again remarks on the singular facts presented
by these islands. Why, he asks, were the aboriginal in-
habitants of the Galapagos created on American types of
organisation, though the two countries differ totally in geolo-
gical character and physical conditions ? Why are so many
of the species peculiar to the separate islands? He "is
astonished at the amount of creative force, if such an expres-
sion may be used, displayed in these small, barren, and rocky
islands ; and still more so at its diverse, yet analogous action
on points so near each other."

The variations which occur in species, as well as the modi-
fications of the same organ in allied species, subjects which
had been much neglected by ordinary naturalists, were con-
stantly noted and commented on. He remarks on the
occasional blindness of the burrowing tucutucu of the Pampas
as supporting the view of Lamarck on the gradually acquired
blindness of the aspalax; on the hard point of the tail of
trigonocephalus, which constantly vibrates and produces a
rattling noise by striking against grass and brushwood, as a
character varying towards the complete rattle of the rattle-
snake ; on the small size of the wild horses in the Falkland
islands, as progressing towards a small breed like the Shetland
ponies of the North; and on the strange fact of the cattle
having increased in size, and having partly separated into two
differently coloured breeds. While collecting the remains of
the great extinct mammals of the Pampas, he was much im-
pressed by the fact that, however huge in size or strange in
form, they were all allied to living South American animals,
as are those of the cave-deposits of Australia to the marsupials
of that country ; and he thereon remarks : " This wonderful
relationship in the same continent between the dead and the
living will, I do not doubt, hereafter throw more light on the
appearance of organic beings on our earth, and their disap-
pearance from it, than any other class of facts."

458 TROPICAL NATURE

He also saw, at this early period, the important fact that
there is some great and constant check to the increase of wild
animals, though most of them breed very rapidly, and, of
course, would increase in a geometrical ratio were some such
check not in constant action. He traces the comparative
rarity of a species to less favourable conditions of existence,
and extinction to the normal action of still more unfavourable
conditions, and compares the destruction of a species by man
and its extinction by its natural enemies as being phenomena
of the same essential nature. The various classes of facts
here referred to seemed to him " to throw some light on the
origin of species — that mystery of mysteries, as it has been
called by one of our greatest philosophers ; " and he tells us
that, soon after his return home in 1837, it occurred to him
" that something might perhaps be made out on this question
by patiently accumulating and reflecting on all sorts of facts
which could possibly have any bearing upon it." We know
from his own statement that he had already perceived that no
explanation but some form of the derivation or development
hypothesis, as it was then termed, would adequately explain
the remarkable facts of distribution and geological succession
which he had observed during his voyage ; yet he tells us
that he worked on for five years before he allowed himself to
speculate on the subject; and then, having formulated his
provisional hypothesis in a definite shape during the next
two years, he devoted another fifteen years to continuous
observation, experiment, and literary research, before he gave
to the astounded scientific world an abstract of his theory in
all its wide-embracing scope and vast array of evidence, in his
epoch-making volume, The Origin of Species.

If we add to the periods enumerated above the five years'
observation and study during the voyage, we find that this
work was the outcome of twenty -seven years of continuous
thought and labour, by one of the most patient, most truth-
loving, and most acute intellects of our age. During all this
long period only a very few of his most intimate friends were
aware that he had departed from the then beaten track of
biological study, while the great body of naturalists only
knew him as a good geologist, as the writer of an interesting
book of travels, and the author of an admirable monograph of

ix THE DEBT OF SCIENCE TO DARWIN 459

the cirripedia or barnacles, as well as of a most ingenious
explanation of the origin and structure of coral-reefs — a
series of volumes which were the direct outcome of his
voyage, and which gave him an established reputation. Even
when the great work at last appeared, few could appreciate
the enormous basis of fact and experiment on which it rested,
until, during the succeeding twenty years, there appeared
that remarkable succession of works which exhibited a sample
(and only a sample) of the exhaustless store of materials and
the profound maturity of thought on which his early volume
was founded. From these various works, aided by some per-
sonal intercourse and a correspondence extending over twenty
years, the present writer will endeavour to indicate the
nature and extent of Darwin's researches.

Studies of Domestic Animals

Although, as we have said, Darwin had early arrived at
the conclusion that allied species had descended from common
ancestors by gradual modification, it long remained to him an
inexplicable problem how the necessary degree of modifica-
tion could have been effected, and he adds : "It would thus
have remained for ever, had I not studied domestic produc-
tions, and thus acquired a just idea of the power of selection."
These researches, very briefly sketched in the first and parts
of the fifth and ninth chapters of the Origin of Species, were
published at length (after a delay of nine years, owing to ill
health) in two large volumes, with the title Animals and Plants
Under Domestication; and no one who has not read these
can form an adequate idea of the wide range and thorough
character of the investigation on which every statement or
suggestion in the former work was founded.

The copious references to authorities show us that he
must have searched through almost the entire literature of
agriculture and horticulture, of horse and cattle breeding, of
sporting, of dog, cat, pigeon, and fowl fancying, including
endless series of reviews, magazines, journals of societies, and
newspapers, besides every scientific treatise bearing in any
way on the subject, whether published in this country, on the
Continent, or in America. The facts thus laboriously gathered
were supplemented by personal inquiries among zoologists and

460 TROPICAL NATURE

botanists, farmers, gardeners, sporting -men, pigeon -fanciers,
travellers, and any one who could possibly afford direct per-
sonal information on any of the matters he was investigating.
Then came his own observation and experiment, to fill up gaps,
to settle doubtful points, or to determine questions the import-
ance of inquiring into which no one had ever suspected ; and
lastly, there was the power of arrangement and comparison,
the originality and depth of thought, which drew out from this
vast mass of heterogeneous materials conclusions of the highest
value as bearing on the question of the possible change of
species, and the means by which it had been brought about.

In order to determine the nature and amount of the varia-
bility of domestic productions, he prepared skeletons of all
the more important breeds of rabbits, pigeons, fowls, and
ducks, as well as of the wild races from which they are
known to have been produced, and showed, both by measure-
ments and by accurate drawings, that not only superficial
characters, but almost every part of the bony structure
varied to such an amount as usually characterises very dis-
tinct species or even distinct genera of wild animals. Another
set of experiments was made by crossing the different breeds
of pigeons and fowls which were most completely unlike the
wild race, with the result that in many cases the offspring
were more like the wild ancestor than either of the parents.
These experiments, supported by a mass of facts observed by
other persons, served to establish the principle of the tend-
ency of crosses to revert to the ancestral form ; and this
principle enabled him to explain the interesting fact of the
frequent appearance of stripes on mules, and occasionally on
dun-coloured horses, on the hypothesis, supported by a mass
of collateral evidence, that the common ancestor of the horse,
ass, and zebra tribe was a partially striped and dun-coloured
animal.

A number of very important conclusions were deduced
from the facts presented by domesticated animals and plants,
a few of which may be here referred to. For example, it
was proved that the parts most selected or which had already
most varied — as the tail in fan-tailed pigeons, which has more
tail-feathers than any one of the 8000 different kinds of
living birds — were most subject to further variation; and

THE DEBT OF SCIENCE TO DARWIN

this showed that, when once any part had begun to change,
variations became more abundant, thus furnishing materials
to render still further change in the same direction compara-
tively easy. This is the secret of the rapid improvement of
breeds or races, and is equally applicable to the formation of
species by natural selection. Again, it was found that in
many cases, when much variation occurred, there was a
tendency to a difference in the sexes which had not before
existed. This has been observed in sheep, in fowls, and in
pigeons, and it is very interesting as indicating the origin of
that wonderful diversity between the two sexes which occurs
in several groups of animals. Another curious fact is the
correlation of parts which occurs in many animals, such as
the tusks and bristles of swine, and the hair and teeth in
some dogs, both increasing or becoming lost together ; the
beak and feet of pigeons, both increasing or diminishing
together ; the colour and size of the leaves and seeds changing
simultaneously in some plants ; and numerous other instances
which serve to explain some of the peculiar characters of
natural objects for which we can discover or imagine no
direct use.

The effect of disuse in causing the diminution of an organ
was exhibited by careful comparison and measurements of
tame and wild birds. The sternum, scapulae, and furcula to
which the muscles used in flight are attached, are found to be
diminished in domestic pigeons, as were the wing-bones in
domestic fowls, the capacity of the skull in tame rabbits, and
the size and strength of the wings in silkworm moths. The
evidence afforded by the breeds of pigeons (which have been
domesticated for so many centuries and in so many parts of
the world) of the process of selection, whether unconscious or
methodical, is very clearly set forth, and serves as a typical
example with which to compare the various phenomena pre-
sented by allied species in a state of nature; and in con-
cluding its discussion, he thus replies to some objections : —

" I have heard it objected that the formation of the several
domestic races of the pigeon throws no light on the origin of
the wild species of the columbidae, because their differences
are not of the same nature. The domestic races, for instance,
do not differ, or hardly at all, in the relative lengths and

462 TROPICAL NATURE

shapes of the primary wing-feathers, in the relative length of
the hind toe, or in habits of life, as in roosting and building
on trees. But the above objection shows how completely
the principle of selection has been misunderstood. It is not
likely that characters selected by the caprice of man should
resemble differences preserved under natural conditions, either
from being of direct service to each species, or from standing
in correlation with other modified and serviceable structures.
Until man selects birds differing in the relative length of the
wing-feathers or toes, etc., no sensible change in these parts
should be expected. . . . With respect to the domestic races
not roosting or building in trees, it is obvious that fanciers
would never attend to or select such changes in habits."

Studies of Cultivated and mid Plants

Still more remarkable, perhaps, is the collection of facts
afforded by plants, which can be so much more easily culti-
vated and experimented upon than animals, while the general
phenomena they present are strikingly accordant in the two
kingdoms. As an example of the great mass of facts afforded
by horticulture, he records that three hundred distinct varie-
ties were produced, in the course of fifty years, from a single
wild rose (Eosa spinosissima). We find in these volumes
enormous collections of facts on bud- variation, or the occur-
rence of changes in the flower or leaf -buds of full-grown
plants, from which new varieties can be and often are pro-
duced; and, after a most full and interesting discussion of
the cases, it is shown that some are probably due to reversion
to an ancestral form, others to reversion to one parent when
the plant has been derived from a cross, and others, again, to
that spontaneous variability which seems to be the universal
characteristic of all living organisms.

Three very interesting chapters are then devoted to the
subject of inheritance, and a host of strange and heretofore
inexplicable facts are brought together, compared, and classi-
fied, and shown to be in accordance with a few general prin-
ciples. Then follow five chapters on crossing and hybridism,
perhaps the most important in the whole work, since they
afford the clue to so much of the varied structure and com-
plex relations of animals and plants. Notwithstanding the

ix THE DEBT OF SCIENCE TO DARWIN 463

enormous mass of facts and observations here given, the
portion relating to plants is often but an abstract of the
results of his own elaborate experiments, carried on for a long
series of years, and given at length in three separate volumes
on The Fertilisation of Orchids, on Cross and Self-Fertilisation of
Plants, and on The Forms of Flowers. These works may be
said to have revolutionised the science of botany, since, for
the first time, they gave a clear and intelligible reason for
the existence of that wonderful diversity in the form, colours,
and structure of flowers, on the details of which the system-
atic botanist had founded his generic and specific distinctions,
but as to whose meaning or use he was, for the most part,
profoundly ignorant. The investigation of the whole subject
of crossing and hybridity had shown that, although hybrids
between distinct species usually produced sterile offspring,
yet crosses between slightly different varieties led to in-
creased fertility ; and, during some experiments on this sub-
ject, Darwin found that the produce of these crosses were
also remarkable for vigour of growth. This led to a long
series of experimental researches, the general result of which
was to establish the important proposition that cross-fertilisa-
tion is of the greatest importance to the health, vigour, and
fertility of plants. The fact that the majority of flowers are
hermaphrodite, and appear to be adapted for self-fertilisation,
seemed to be opposed to this view, till it was found that, in
almost every case, there were special arrangements for ensur-
ing, either constantly or occasionally, the transference of pollen
from the flowers of one plant to those of another of the same
species. In the case of orchids, it was shown that those
strange and beautiful flowers owed their singular and often
fantastic forms and exceptional structure to special adapta-
tions for cross-fertilisation by insects, without the agency of
which most of them would be absolutely sterile. Many of
the species are so minutely adapted to particular species or
groups of insects, that they can be fertilised by no others ;
and careful experiment and much thought was often required
to find out the exact mode in which this was effected. In
some instances the structure of the flowers seemed adapted to
prevent fertilisation altogether, till it was at length discovered
that a particular insect entering the flower in one particular

464 TROPICAL NATURE

way caused the pollen to stick to some part of its body,
which was always the exact part which the insect, on visiting
another flower, would bring in contact with the stigma, and
thus fertilise it. These investigations explained a host of
curious facts which had hitherto been facts only without
meaning, such as the twisting of the ovary in most of our
wild orchids, which was found to be often necessary to bring
the flower into a proper position for fertilisation, — the exist-
ence of sacs, cups, or spurs, the latter often of enormous
length, but shown to be each adapted to the structure of
some particular insect, and often serving to prevent other
insects from reaching the nectar which they might rob with-
out fertilising the flower, — the form, size, position, rugosities,
or colour of the lip, serving as a landing-place for insects and
a guide to the nectar-secreting organs, — the varied odours,
sometimes emitted by day, and sometimes by night only,
according as the fertilising insect was diurnal or nocturnal,
and other characters too numerous to refer to here, so that it
became evident that every peculiarity of these wonderful
plants, in form or structure, in colour or marking, in the
smoothness, rugosity, or hairiness of parts of the flower, in
their times of opening, their movements, or their odours, had
every one of them a purpose, and were, in some way or other,
adapted to secure the fertilisation of the flower and the pre-
servation of the species.

Researches on the Cowslip, Primrose, and Loosestrife
The next set of observations, on some of our commonest
English flowers of apparently simple structure, were not less
original and instructive. The cowslip (Primula veris) has
two kinds of flowers in nearly equal proportions : in the one
the stamens are long and the style short, and in the other the
reverse, so that in the one the stamens are visible at the
mouth of the tube of the flower, in the other the stigma
occupies the same place, while the stamens are half-way down
the tube. This fact had been known to botanists for seventy
years, but had been classed as a case of mere variability, and
therefore considered to be of no importance. In 1860 Darwin
set to work to find out what it meant, since, according to his
views, a definite variation like this must have a purpose.

ix THE DEBT OF SCIENCE TO DARWIN 465

After a considerable amount of observation and experiment,
he found that bees and moths visited the flowers, and that
their probosces became covered with pollen while sucking up
the nectar, and further, that the pollen of a long-stamened
plant would be most surely deposited on the stigma of the
long-styled plants, and vice versd. Now followed a long series
of experiments, in which cowslips were fertilised either with
pollen from the same kind or from a different kind of flower,
and the invariable result was that the crosses between the
two different kinds of flowers produced more good capsules,
and more seeds in each capsule ; and as these crosses would
be most frequently effected by insects, it was clear that this
curious arrangement directly served to increase the fertility
of this common plant.

The same thing was found to occur in the primrose, and
in many other species of primulacese, as well as in flax (Linum
perenne), lungworts (Pulmonaria), and a host of other plants,
including the American partridge -berry (Mitchella repens).
These are called dimorphic heterostyled plants.

Still more extraordinary is the case of the common loose-
strife (Lythrum salicaria), which has both stamens and styles
of three distinct lengths, each flower having two sets of
stamens and one style, all of different lengths, and arranged
in three different ways : (1) a short style, with six medium
and six long stamens ; (2) a medium style, with six short and
six long stamens ; (3) a long style, with six medium and six
short stamens. These flowers can be fertilised in eighteen
distinct ways, necessitating a vast number of experiments,
the result being, as in the case of the cowslip, that flowers
fertilised by the pollen from stamens of the same length as
the styles, gave on the average a larger number of capsules
and a very much larger number of seeds than in any other
case. The exact correspondence in the length of the style of
each form with that of the stamens in the two other forms
ensures that the pollen attached to any part of the body of
an insect shall be applied to a style of the same length on
another plant, and there is thus a triple chance of the maxi-
mum of fertility. Some other species of lythrum, of oxalis,
and pontederia, were also found to have three-formed stamens
and styles ; and in the case of the oxalis, experiments were
2H

466 TROPICAL NATURE

made showing that crosses between flowers with stamens and
styles of unequal length were always nearly barren. During
these experiments 20,000 seeds of Lythrum salicaria were
counted under the microscope. For several years a further
supplementary series of experiments were carried out, show-
ing that the seeds produced by the illegitimate crosses (as he
terms them) were not only very few, but, when sown, always
produced comparatively weak, small, or unhealthy plants, not
likely to exist in competition with the stronger offspring of
legitimate crosses. There is thus the clearest proof that these
complex arrangements have the important end of securing
both a more abundant and more vigorous offspring.

Perhaps no researches in the whole course of the study of
nature have been so fertile in results as these. No sooner
were they made known than observers set to work in every
part of the world to examine familiar plants under this new
aspect. With very few exceptions it is now found that every
flower presents arrangements for securing cross-fertilisation,
either constantly or occasionally, sometimes by the agency of
the wind, but more frequently through the mediation of
insects or birds. Almost all the irregularity and want of
symmetry in the forms of flowers, which add so much to their
variety and beauty, are found to be due to this cause ; the
production of nectar and the various nectar-secreting organs
is directly due to it, as are the various odours and the various
colours and markings of flowers. In many cases flowers which
seem so simply constructed that the pollen must fall on the
stigma and thus produce self-fertilisation, are yet surely cross-
fertilised, owing to the circumstance of the stigma and the
anthers arriving at maturity at slightly different periods, so
that, though the pollen may fall on the stigma of its own
flower, fertilisation does not result ; but when insects carry
the pollen to another plant the flowers of which are a little
more advanced, cross-fertilisation is effected. There is liter-
ally no end to the subjects of inquiry thus opened up, since
every single species, and even many varieties of flowering
plants, present slight peculiarities which modify to some
extent their mode of fertilisation. This is well shown by the
remarkable observations of the German botanist Kerner, who
points out that a vast number of details in the structure of

ix THE DEBT OF SCIENCE TO DARWIN 467

plants, hitherto inexplicable, are due to the necessity of keep-
ing away " unbidden guests," such as snails, slugs, ants, and
many other kinds of animals, which would destroy the flowers
or the pollen before the seeds were produced. When this
simple principle is once grasped, it is seen that almost all the
peculiarities in the form, size, and clothing of plants are to
be thus explained, as the spines or hairs of the stem and
branches, or the glutinous secretion which effectually pre-
vents ants from ascending the stem, the drooping of the
flowers to keep out rain or to prevent certain insects from
entering them, and a thousand other details which are de-
scribed in Kerner's most instructive volume. This branch of
the inquiry was hardly touched upon by Darwin, but it is
none the less a direct outcome of his method and his teaching.

The Struggle for Existence

But we must pass on from these seductive subjects to give
some indication of the numerous branches of inquiry of which
we have the results given us in the Origin of Species, but
which have not yet been published in detail. The observa-
tions and experiments on the relations of species in a state of
nature, on checks to increase and on the struggle for existence,
were probably as numerous and exhaustive as those on domes-
ticated animals and plants. As examples of this we find
indications of careful experiments on seedling plants and
weeds, to determine what proportion of them were destroyed
by enemies before they came to maturity ; while another set
of observations determined the influence of the more robust
in killing out the weaker plants with which they come into
competition. This last fact, so simple in itself, yet so much
overlooked, affords an explanation of many of the eccentrici-
ties of plant distribution, cultivation, and naturalisation.
Every one who has tried it knows the difficulty or impossi-
bility of getting foreign plants, however hardy, to take care
of themselves in a garden as in a state of nature. Wherever
we go among the woods, mountains, and meadows of the
temperate zone, we find a variety of charming flowers growing
luxuriantly amid a dense vegetation of other plants, none of
which seem to interfere with each other. By far the larger
number of these plants will grow with equal luxuriance in

468 TROPICAL NATURE

our gardens, showing that peculiarities of soil and climate, are
not of vital importance ; but not one in a thousand of these
plants ever runs wild with us, or can be naturalised by the
most assiduous trials ; and if we attempt to grow them under
natural conditions in our gardens, they very soon succumb
under the competition of the plants by which they are sur-
rounded. It is only by constant attention, not so much to
them as to their neighbours — by pruning and weeding close
around them so as to allow them to get a due proportion of
light, air, and moisture, that they can be got to live. Let
any one bring home a square foot of turf from a common or
hill-top, containing some choice plant growing and flowering
luxuriantly, and place it in his garden, untouched, in the
most favourable conditions of light and moisture, and in a
year or two it will almost certainly disappear, killed out by
the more vigorous growth of other plants. The constancy of
this result, even with plants removed only a mile or two, is a
most striking illustration of the preponderating influence of
organism on organism, that is, of the struggle for existence.
The rare and delicate flower which we find in one field or
hedgerow, while for miles around there is no trace of it,
maintains itself there, not on account of any specialty of soil
or aspect, or other physical conditions being directly favour-
able to itself, but because in that spot only there exists the
exact combination of other plants and animals which alone is
not incompatible with its wellbeing, that combination perhaps
being determined by local conditions or changes which many
years ago allowed a particular set of 'plants and animals to
monopolise the soil and thus keep out intruders. Such con-
siderations teach us that the varying combinations of plants
characteristic of almost every separate field or bank, or hill-
side, or wood throughout our land, is the result of a most
complex and delicate balance of organic forces — the final
outcome for the time being of the constant struggle of plants
and animals to maintain their existence.

Geographical Distribution and Dispersal of Organisms
Another valuable set of experiments and observations are
those bearing on the geographical distribution of animals and
plants — a branch of natural history which, under the old idea

ix THE DEBT OF SCIENCE TO DARWIN 469

of special creations, had no scientific existence. It is to
Darwin that we owe the establishment of the distinction of
oceanic from continental islands, while he first showed us the
various modes by which the former class of islands have been
stocked with life. By a laborious research in all the accounts
of old voyages, he ascertained that none of the islands of the
great oceans very remote from land possessed either land
mammalia or amphibia when first visited ; and on examina-
tion it is found that all these islands are either of volcanic
origin or consist of coral reefs, and are therefore presumably
of comparatively recent independent origin, not portions of
submerged continents, as they were formerly supposed to be.
Yet these same islands are fairly stocked with plants, insects,
land-shells, birds, and often with reptiles, more particularly
lizards, usually of peculiar species, and it thus becomes
important to ascertain how these organisms originally reached
the islands, and the comparative powers different groups of
plants and animals possess of traversing a wide extent of ocean.
With this view he made numerous observations and some
ingenious experiments. He endeavoured to ascertain how
long different kinds of seeds will resist the action of salt
water without losing their vitality, and the result showed
that a large number of seeds will float a month without
injury, while some few survived an immersion of one hundred
and thirty-seven days. Now, as ocean currents flow on the
average thirty-three miles a day, seeds might easily be carried
1000 miles, and in very exceptional cases even 3000 miles,
and still grow. Again, it is known that drift-timber is often
carried enormous distances, and some of the inhabitants of
the remote coral-islands of the Pacific obtain wood by this
means, as well as stones fastened among the roots. Now,
Darwin examined torn -up trees, and found that stones are
often inclosed by the roots growing round them so as to leave
closed cavities containing earth behind; and from a small
portion of earth thus completely inclosed, he raised three
dicotyledonous plants. Again, the seeds that have passed
through the bodies of birds germinate freely, and thus birds
may carry plants from island to island. Earth often adheres
to the feet of aquatic and wading birds, and these migrate to
enormous distances and visit the remotest islands, and from

470 TROPICAL NATURE

earth thus attached to birds' feet several plants were raised.
As showing the importance of this mode of transport, an
experiment was made with six and three -fourths ounces of
mud taken from the edge of a little pond, and it was found
to contain the enormous number of five hundred and thirty-
seven seeds of several distinct species ! This was proved by
keeping the mud under glass and pulling up each plant as it
appeared, and at the end of six months the result was as
given above. It was also found that small portions of aquatic
plants were often entangled in the feet of birds, and to these
as well as to the feet themselves, molluscs or their eggs were
found to be attached, furnishing a mode of distribution for
such organisms. Experiments were also made on the power
of land-shells to resist the action of sea- water ; and we have
already referred to the observations on volcanic dust carried
far out to sea, illustrating the facilities for the wide extension
by aerial currents of such plants as have very minute or very
light seeds. l The facts are of so anomalous and apparently
contradictory a character that, on the old hypothesis of the
special independent creation of each species, no rational
explanation of them could be found ; and we may fairly
claim that the clear and often detailed explanation which can
be given by means of the theories and investigations of
Darwin, lend a powerful support to his views, and go far to
complete the demonstration of their correctness.

Our space will not permit us to do more than advert to
the numerous ingenious explanations and suggestions with
which the Origin of Species abounds, such as, for example, the
strange fact of so many of the beetles of Madeira being wing-
less, while the same species, or their near allies on the con-
tinent of Europe, have full powers of flight ; and that this is
not due to any direct action of climate or physical conditions
is proved by the equally curious fact that such species of
insects as have wings in Maderia, have them rather larger
than usual. Equally new and important is the Darwinian
explanation of the form of the bees' cell, which is shown to

i This series of observations and experiments, supplemented by those of
other observers, have been applied by the writer of this article to explain in
some detail the remarkable phenomena presented by the distribution of
animals and plants over the chief islands of the glooe. See Island Life.
Macmillan and Co.

ix THE DEBT OF SCIENCE TO DARWIN 471

be due to a few simple instincts which necessarily lead to the
exact hexagonal cell with the base formed of three triangular
plates inclined at definite angles, on which so much mathema-
tical learning and misplaced admiration have been expended ;
and this explanation is no theory, but is the direct outcome
of experiments on the bees at work, as original as they were
ingenious and convincing.

The Descent of Man and Later Works

We must, however, pass on to the great and important work,
The Descent of Man and on Selection in Relation to Sex, which
abounds in strange facts and suggestive explanations; and
for the reader who wishes to understand the character and
bearing of Darwin's teachings, this book is the fitting supple-
ment to the Origin of Species and the Domesticated Animals and
Plants. To give any adequate account of this most remark-
able book and the controversies to which it has given rise,
would require an article to itself. We refer to it here in
order to point out what is not generally known, that its
publication was entirely out of its due course, and was not
anticipated by its author three years before. In the intro-
duction to Domesticated Animals (published in 1868), after
explaining the scope of that work, he tells us that in a
second work he shall treat of "Variation Under Nature,"
giving copious facts on variation, local and general, on races,
sub-species and species, on geometrical increase, on the struggle
for existence, with the results of experiments showing that
diversity of forms enables more life to be supported on a
given area, while the extermination of less improved forms,
the formation of genera and families, and the process of
natural selection, will be fully discussed. This work would
have given all the facts on which chapters ii. to v. of the
Origin of Species were founded. In a third work he proposed
to show, in detail, how many classes of facts natural selection
explains, such as geological succession, geographical distribu-
tion, embryology, affinities, classification, rudimentary organs,
etc., etc., thus giving the facts and reasonings in full on
which the latter part of the Origin of Species was founded.
Unfortunately, neither of these works has appeared, and thus
the symmetry and completeness of the body of facts which

472 TROPICAL NATURE

Darwin had collected have never been made known. The
cause is well known to have been the continued pressure of
ill -health. The work on Domesticated Animals was thus
delayed many years, after which came the labour of bringing
out a much enlarged edition of the Origin of Species. The
Descent of Man was, apparently, at first intended to be a
comparatively small book, but a difficulty connected with the
origin of the distinctive peculiarities of the two sexes led to
an investigation of this subject throughout the animal king-
dom. This was found to be of such extreme interest, and to
have such important applications, that its development with
the completeness characteristic of all the writer's work led to
the production of two bulky volumes, followed by another
volume on the Expression of the Emotions in Man and Animals,
not less instructive. None of Darwin's works has excited
greater interest or more bitter controversy than that on man;
and the correction of the numerous reprints, and of a final
enlarged edition in 1874, was found to be so laborious a task
as to convince him that any such extensive literary works as
those projected and announced six years previously must be
finally abandoned. This, however, by no means implied
cessation from work. Observation and experiment were the
delight and relaxation of Darwin's life,1 and he now con-
tinued and supplemented those numerous researches on plants
we have already referred to. A new edition of an earlier
work on the Movements of Climbing Plants appeared in 1875 ;
a thick volume on Insectivorous Plants in the same year;
Cross and Self -Fertilisation in 1876 ; the Forms of Flowers in
1877; the Movements of Plants, embodying much original
research, in 1880; and his remarkable little book on Earth-
worms in 1881. This last work is highly characteristic of
the author. In 1837 he had contributed to the Geological
Society a short paper on the formation of vegetable mould
by the agency of worms. For more than forty years this
subject of his early studies was kept in view ; experiments
were made, in one case involving the keeping a field untouched
for thirty years, — and every opportunity was taken of collect-

i About this time he said to the present writer : " When I am obliged to
give up observation and experiment, I shall die." And he actually did con-
tinue his experiments to within a few days of his death.

ix THE DEBT OF SCIENCE TO DARWIN 473

ing facts and making fresh observations, the final result being
to elevate one of the humblest and most despised of the
animal creation to the position of an important agent in the
preparation of the earth for the use and enjoyment of the
higher animals and of man.

The sketch now given of Darwin's work, though it may have
seemed tedious to the reader by its length, is yet in many
respects imperfect, since it has given no account of those
earlier important labours which would alone have made the
reputation of a lesser man. None but the greatest geologists
have produced more instructive works than the two volumes
of Geological Observations, and the profound and original essay
" On the Structure and Distribution of Coral Reefs " ; the
most distinguished zoologists and anatomists might be proud
of the elaborate " Monograph of the Cirripedia," of which a
competent judge says : " The prodigious number and minute
accuracy of his dissections, the exhaustive detail with which
he worked out every branch of his subject — sparing no pains
in procuring every species that it was possible to procure, in
collecting all the known facts relating to the geographical and
geological distribution of the group, in tracing all the compli-
cated history of the metamorphoses presented by the indivi-
duals of the sundry species, in disentangling the problem of
the homologies of these perplexing animals, etc. — all combine to
show that, had Mr. Darwin chosen to devote himself to a life
of morphological work, his name would probably have been
second to none in that department of biology,"1 while the
numerous researches on the fertilisation and structure of
flowers and the movements of plants, would alone place him
in the rank of a profound and original investigator in botanical
science.

Estimate of Darwin's Life- Work

Yet these works, great as is each of them separately, and,
taken altogether, amazing as the production of one man, sink
into insignificance as compared with the vast body of research
and of thought of which the Origin of Species is the brief
epitome, and with which alone the name of Darwin is
associated by the mass of educated men. I have here
1 Nature, vol. xxvi. p. 99.

474 TROPICAL NATURE

endeavoured, however imperfectly, to enable non- specialists
to judge of the character and extent of this work, and of the
vast revolution it has effected in our conception of nature, —
a revolution altogether independent of the question whether
the theory of " natural selection " is or is not as important a
factor in bringing about changes of animal and vegetable
forms as its author maintained. Let us consider for a
moment the state of mind induced by the new theory and
that which preceded it. So long as men believed that every
species was the immediate handiwork of the Creator, and was
therefore absolutely perfect, they remained altogether blind
to the meaning of the countless variations and adaptations of
the parts and organs of plants and animals. They who were
always repeating, parrot-like, that every organism was exactly
adapted to its conditions and surroundings by an all -wise
being, were apparently dulled or incapacitated by this belief
from any inquiry into the inner meaning of what they saw
around them, and were content to pass over whole classes of
facts as inexplicable, and to ignore countless details of structure
under vague notions of a " general plan," or of variety and
beauty being " ends in themselves " ; while he whose teachings
were at first stigmatised as degrading or even atheistical, by
devoting to the varied phenomena of living things the loving,
patient, and reverent study of one who really had faith in the
beauty and harmony and perfection of creation, was enabled
to bring to light innumerable hidden adaptations, and to prove
that the most insignificant parts of the meanest living things
had a use and a purpose, were worthy of our earnest study,
and fitted to excite our highest and most intelligent admiration.
That he has done this is the sufficient answer to his critics
and to his few detractors. However much our knowledge of
nature may advance in the future, it will certainly be by
following in the pathways he has made clear for us ; and for
long years to come the name of Darwin will stand for the
typical example of what the student of nature ought to be.
And if we glance back over the whole domain of science, we
shall find none to stand beside him as equals ; for in him we
find a patient observation and collection of facts, as in Tycho
Brahe ; the power of using those facts in the determination of
laws, as in Kepler, combined with the inspirational genius of a

ix THE DEBT OF SCIENCE TO DARWIN 475

Newton, through which he was enabled to grasp fundamental
principles, and so apply them as to bring order out of chaos,
and illuminate the world of life as Newton illuminated the
material universe. Paraphrasing the eulogistic words of the
poet, we may say, with perhaps a greater approximation to
truth—

" Nature and Nature's laws lay hid in night;
God said, ' Let Darwin be,' and all was light."

INDEX

ABBOTT, C. C., on American palaeo-
lithic implements, 441
Abbott, Dr., on nests of Baltimore

oriole, 114

Abraxas grossulariata, 84
Abrus precatoria, perhaps a case of

mimicry, 399

Absorption-colours or pigments, 357
Acanthotritus dorsalis, 67
Accipiter pileatus, 75
Acraeidae, the subjects of mimicry, 61

warning colours of, 350
Acronycta psi, protective colouring of,

45
Adaptation brought about by general

laws, 149

looks like design, 152
Adaptive characters, 331, 335
JEgeriidae, mimic Hymenoptera, 64
Affinities, how to determine doubtful,

330
Agassiz on embryonic character of

ancient animals, 165
Agnia fasciata, mimics another Longi-

corn, 68
Agriopis aprilina, protective colouring

of, 45
Alcedinidae, sexual colouring and

nidification of, 124
Aleutian islands, ancient shell mounds

in, 437
Allen, Mr. Grant, on protective

colours of fruits, 398
Alpine flowers, why so beautiful, 403
Amadina, sexual colouring and nidifi-
cation of, 126
Amboyna, large -sized butterflies of,

385
American monkeys, 306

Ampelidae, sexual colouring and nidifi-
cation of, 126
Ancient races of North and South

America, 429
Ancylotherium, 165
Andaman islands, pale butterflies of,
386

white-marked birds of, 388
Anderson, Mr. W. Marshall, on
cranium from N. American mound,
428

Andes, very rich in humming-birds, 323
Andrenidae, 70
Angrsecum sesquipedale, 146

its fertilisation by a large moth,

148
Animal colours, how produced, 357

life in tropical forests, 271
Animals, senses and faculties of, 89
intellect of, compared with that

of savages, 192

and plants under domestication,
an example of Darwin's re-
search, 459
Anisocerinae, 66
Anoplotherium, 165
Anthribidaj, 290

mimicry of, 67
Anthrocera filipendulae, 84
Anthropologists, wide difference of
opinion among, as to origin of
human races, 167

conflicting views of, harmonised,

179

Antiquity of man, 167, 180

in North America, 433

Ants, wasps, and bees, 278

numbers of, in India and Malaya,
278, 283

INDEX

477

Ants, destructive to insect-specimens,
281
and vegetation, special relation

between, 284
Apathus, 70

Apatura and Heterochroa, resemblance
of species of, 384

Apparent exceptions to law of colour

and nidification, 133
Aquatic birds, why abundant, 25
Aqueous vapour of atmosphere, its
influence on temperature, 223
quantity at Batavia and Clifton,

224

Archaeopteryx, 165
Archegosaurus, 165
Architecture of most nations deriva-
tive, 113

Grecian, false in principle, 114
Arctic animals, white colour of, 37, 38
plants, large leaves of, 407
flowers and fruits brightly

coloured, 407
Areca palm, 252
Arenga saccharifera, 250
Argus-pheasant, wonderful plumage

of, 374

Argyll, Duke of, on colours of wood-
cock, 39

on mind in nature, 141
criticism on Darwin's works,

144

on humming-birds, 153
on creation by birth, 156
Arums, 254
Asilus, 69
Aspects of nature as influencing man's

development, 176
Assai of the Amazon, 250
Auckland isles, handsome flowers of,

408

Audubon, on the ruby humming-
birds, 317, 322
Azara, on food of humming-birds, 320

BALANCE in nature, 32
Bamboos, 257

uses of, 258-262
Banana, 254
Bananas, wild, 254
Barber, Mrs., on colour changes of
pupa of Papilio nireus, 345

Barbets, 297

Bark, varieties in tropical forests, 243
Barometer, range of, at Batavia, 234
Barrington, Hon. Daines, on song of
birds, 104

on danger of song and gay plum-
age to female birds, 138
Batavia, meteorology of, 219

and London, diagram of mean

temperatures, 220
greatest rainfall at, 235
range of barometer at, 234
Bates, Mr., first adopted the word
"mimicry," 54
his observations on Leptalis and

Heliconidae, 59
his paper explaining the theory

of mimicry, 59
objections to his theory, 76
on recent immigration of Ama-
zonian Indians, 100
on climate at the equator, 235
on scarcity of forest-flowers on

Amazon, 264
on animal life in Amazon valley,

271
on abundance of butterflies at Ega,

274

on importance of study of butter-
flies, 277

on leaf-cutting ants, 282
on blind ants, 284
on bird-catching spider, 291
on use of Toucan's bill, 298
on large serpents, 304
on the habits of humming-birds,

318

Bats, 307

Bayma, Mr. , on " Molecular Me-
chanics," 208

Beagle, Darwin's voyage in, 455
Beauty in nature, 153
not universal, 155
of flowers useful to them, 155
not given for its own sake, 156
Beetles, 288

abundance of, in new forest clear-
ings, 290

probable use of horns of, 372
Belt, Mr., on virgin forests of Nicar-
agua, 265
on aspects of tropical vegetation,

478

INDEX

Belt, Mr., on leaf-cutting ants, 283
on an Acacia inhabited by ants,

285
on uses of ants to the trees they

live on, 285

on a leaf-like locust, 288
on tree-frogs, 305
on the habits of humming-birds,

319
on uneatable bright-coloured frog,

351

on use of light of glow-worm, 374
Berthoud, on stone implements in

tertiary deposits in America, 448
Betel-nut, 252
Bill of humming-birds, 315
Birds, possible rapid increase of, 23
numbers that die annually, 24
mimicry among, 73
dull colour of females, 80
nidification as affecting colour of

females, 81

refusing the gooseberry cater-
pillar, 84
why peculiar nest built by each

species, 101, 103
build more perfect nests as they

grow older, 108

on instincts of newly-hatched, 109
alter and improve their nests, 114
sexual differences of colour in, 123
tropical orders of, 292
how many known, 312
influence of locality on colours

of, 382
cases of local variation of colour

among, 387
Bombus hortorum, 64
Bombycilla garrula, colours and

nidification of, 134
Bombylius, 69
Bonelli, Mr., on the Sappho comet

humming-bird, 318
Brain of the savage but slightly less
than that of civilised man, 188
size of, an important element of

mental power, 188
of savage races larger than their

needs require, 190, 193
of man and of anthropoid apes

compared, 190
Broca, Professor Paul, on the fine
crania of the cave men, 189

Bryophila glandifera and B. perla pro-
tectively coloured, 46
Bucerotidae, sexual colouring and

nidification of, 125
Bucconidae, sexual colouring and

nidification of, 125
Buff -tip moth, resembles a broken

tick, 45
Buildings of various races do not

change, 99
Bullock on food of humming-birds,

320

Buprestidae, resembling bird's dung,
42

similar colours in two sexes, 80
in tropical forests, 289
Burchell, Dr., on the "stone mesem-

bryanthemum," 396
Butterflies, abundance of, in tropical
forests, 272

conspicuousness in tropical forests,

273

colours and form of, 273
peculiar habits of tropical, 275
tropical and temperate compared

as to colour, 342
females do not choose their part-
ners, 370

with gaily coloured females, 373
influence of locality on colours of,

382
Buttressed trees, 241

CACIA anthriboides, 67

Caelogynes, 257

Calamus, 249

Calaveras skull found in auriferous
gravel, 447

California, auriferous gravels of, 442

Callithea, imitated by species of Cata-
gramma and Agrias, 383

Callithea markii, 274

Callizona acesta, protective colouring
of, 43

Calornis, 123

Campylopterus hemileucurus pug-
nacious and ornamental, 380

Capitonidae, sexual colouring and
nidification of, 125

Capnolymma stygium, 67

Carabidae, special protection among,
52

similar colouring of two sexes, 80

INDEX

479

Cassidae, resemble dew-drops, 42
Caterpillars, mimicking a poisonous

snake, 70

gaudy colours of, 82

various modes of protection of,

83

gooseberry caterpillar, 84
Mr. Jenner Weir's observations

on, 84
Mr. A. G. Butler's observations

on, 85

Cattleyas, 257

Cecropias, trees inhabited by ants, 285
Celebes, large and peculiarly formed

butterflies of, 385

white-marked birds of, 388
Centipedes, 291
Centropus, sexual colouring and nidifi-

cation of, 125
Cephalodonta spinipes, 66
Ceroxylus laceratus, imitates a moss-
covered stick, 47
Certhiola, sexual colouring and nidifi-

cation of, 127
Cetoniadse, how protected, 53

similar colours of two sexes, 80
Chaffinch, curious nest built by, in

New Zealand, 111
Chameleon, cause of changes of its

colour, 347
Chameleons, 303
Charis melipona, 68
Chematobia, wintry colours of this

genus, 45

Chemical action changes colours, 357
Chili, humming-birds of, 324
Chiroptera, 307
Chlamys pilula, resembles dung of

caterpillars, 42

Chrysididse, how protected, 52
Chrysobactron Rossii, 408
Chrysomelidae, similar colouring of

two sexes, 80
Cicindela, adaptive colour of various

species of, 42
Cilix compressa, resembles bird's

dung, 46

Cladobates, mimicking squirrels, 76
Claparede, M., criticism on Mr.

Wallace's views as to origin of man,

205 (note)
Clark, Rev. Hamlet, on leaf-cutting

ants, 282

Classification, form of true, 6
circular, inadmissible, 7
quinarian and circular, of Swain-
son, 34

argument from, against Mr. Dar-
win, 162
Climacteris, sexual colouring and

nidification of, 126
Climate of Equator, general features

of, 229

Climates of Timor, Angola, and Scot-
land compared, 227
Climbing plants of tropical forests,
246

uses of, 247
Coccinellidae, how protected, 52

similar colouring of sexes, 80
Cockatoos, 293

Cocos islands visited by Darwin, 456
Collyrodes lacordairei, 67
Coloration of tropical birds, 300
Colour, in animals, popular theories
of, 36

frequent variations of, in domes-
ticated animals, 36
influenced by need of conceal-
ment, 37
in deserts, 37
in arctic regions, 37, 38
nocturnal, 38
tropical, 38

special modifications of, 39
different distribution of, in butter-
flies and moths, 43
of autumnal and winter moths, 45
white, generally dangerous and

therefore eliminated, 48
why it exists so abundantly

although often injurious, 50
influenced by need of protection,

80

of female birds, 80
in relation to nidification of birds,

81

gaudy colours of many cater-
pillars, 82

in nature, general causes of, 88
sexual differences of, in birds, 123
in female birds, how connected
with their nidification, 124, 128
more variable than structure or
habits, and therefore more
easily modified, 130

INDEX

Colour of flowers, as explained by Mr.
Darwin, 139

often correlated with disease, 175

cause of change of, in humming-
birds, 327

in nature, problems of, 339

how far constant, 340

as affected by heat and light, 341

of tropical birds, 342

of tropical butterflies, 342

of temperate and tropical flowers,
343

changes of, in animals produced
by coloured light, 345

voluntary change of, in animals,
347

not usually influenced by coloured
light, 348

the nature of, 354

how produced, 357

changed by heat, 357

a normal product of organisation,
359

as a means of recognition, 367

proportionate to integumentary
development, 368

not caused by female selection,
369

absent in wind-fertilised flowers,
404

same theory of, in animals and
plants, 405

of flowers and their distribution.
405

nomenclature of, formerly im-
perfect, 414

Colour -development as illustrated in
humming-birds, 379

local causes of, 382
Colour -perception, supposed recent

growth of, 412
Colour-sense, origin of the, 410

need for, 411

not of recent origin, 414

not wholly explicable, 415
Colours, classification of organic, 348

protective, 349

warning, 350

sexual, 352

normal, 354

of animals, how produced, 357

theory of protective, 360

theory of warning, 361

Colours, theory of sexual, 364
theory of normal, 381
of fruits, attractive, 397
protective, 398
which first perceived, 411
Colours and ornaments of humming-
birds, 314
Cometes sparganurus, very pugnacious,

381

Compsognathus, 165
Condylodera tricondyloides, 69
Consciousness, origin of, 206
Professor Tyndall on, 206
not a product of complex organi-
sation, 209
an advance on mere vegetative

life, 209 (note)
Copridse, 289

probable use of horns of, 372
Coral-reefs and cirripedia, Darwin's

works on, 473
Correlation of growth, 172
Corynomalus sp., 66
Cotingidse, sexual colouring and nidifi-

cation of, 127

Cratosomus, a hard weevil, 67
Crematogaster, gems of ants, 280
Crickets mimicking sand wasps, 70
Cross -fertilisation of flowers, .use of,
400

complex arrangements for, 401
Crossing and inheritance studied by

Darwin, 462
Cryptodontia, 164
Cuckoos, 296
Cucullia verbasci, 84
Curculionidae, often protected by hard
covering, 51

similar colours of two sexes, 80
Cuviera squamata, 136
Cyclopeplus batesii, 66

DANAID^E, the subjects of mimicry,
61, 62 •

warning colours of, 350
Danainse, Acraeinae, and Heliconiinae,

local resemblances of, 383
Danais archippus, 63

chrysippus, 79
Daphne pontica, 402
Darwin, Mr., extract from letter from,
21

his principle of utility, 35

INDEX

481

Darwin, Mr., on colours of caterpillars,
83

on cause of colour in flowers, 89,

139

on sexual coloration, 138
his metaphors liable to miscon-
ception, 144
criticism of, in North British

Review, 159
on mode of cross-fertilisation and

its use, 400
debt of science to, 450
his voyage in the Beagle, 455
on dust collected 300 miles from

land, 456
on productions of Cocos anfl

Galapagos islands, 456
the origin of species, 458
animals and plants under do-
mestication, 459
observations on variability, 460
observations on use and disuse,

461

the fertilisation of orchids, 463
on crossing and hybridity, 463
on cowslip and primrose, 464
on Lythrum salicaria, 465
on enemies of seedling plants, 467
on oceanic and continental islands,

469

on vitality of seeds, 469
on seeds in mud, 470
The descent of man, 471
Expression of the emotions, 472
Climbing and Insectivorous

plants, 472
on coral reefs and cirripedia,

473
revolution in thought effected by

him, 473

summary of his work, 473
Desert animals, colours of, 37
Deserts on line of tropics, 239
Desmoncus, 249

De Vry, Mr., on the sugar- palm, 251
Dews, cause of heavy tropical, 224
Diadema, species of, mimic Danaidae,
61, 62

female with male coloration, 79
D. misippus, 79
D. anomala, 80

Diagram of mean temperature at Bat-
avia and London, 220

2

Diagram of rainfall at London and

Batavia, 228

Dianthus alpinus, D. glacialis, 404
Diaphora mendica, 64
Dicnyodontia, 164
Dicrourus, 133
Diloba caeruleocephala, 84
Dinosauria, 164
Diptera mimicking wasps and bees,

69

Distribution of humming-birds, 322
Disuse, effects of, studied by Darwin,

461
Dixon, Mr. Charles, on nest of a

chaffinch in New Zealand, 111
Doliops curculionides, 67
Domesticated animals, their essential

difference from wild ones, 30, 31
Dotterell, 132

Dragons or flying-lizards, 303
Drugs from equatorial forest-trees, 245
Duke of York island, pale coloured

insects of, 385

islands, remarkable white plum-

Dyes from equatorial forest-trees, 245
Dynastidae, 289

probable use of horns of, 372

EARTH-WORKS, North American, 425
Earth-worms, Darwin's work on, 472
Easter island, sculptures on, 424
Eciton, genus of foraging ants, 283
Egyptian architecture, introduced, 113
Elaps fulvius, E. corallinus, E. lemnis-

catus, E. mipartitus, E. hemi-

prichii, 72
Elateridse, luminous species, perhaps

mimetic, 374
Emperor-moth, protective coloration

of, 350
Ennomos, autumnal colours of this

genus, 45
Epicalia, sexes of, differently coloured,

353
Epilobium angustifolium, E. parvi-

florum, 404
Epimachinse, 332

Equator, cause of uniform high temper-
ature near, 221

short twilight at, 232
Equatorial climate, general features of,

229

INDEX

Equatorial climate, uniformity of, in all

parts of the world, 230

local diversities of, 231
Equatorial zone, temperature of, 219
heavens, aspect of, 234
forest-belt, cause of, 238
forests, general features of, 240
Equus, 164
Eroschema poweri, 66
Erycinidae mimic Heliconidse, 60
Erythroplatis corallifer, 66
Estrelda, sexual colouring and nidifi-

cation of, 126
Eucnemidae, mimicking a Malaco-

derm, 66

Eudromias morinellus, 132
Eugenes fulgens, 319
Euglossa dimidiata, 69
Eumorphidae, a protected group, 52

imitated by Longicorns, 65
Eunica and Siderone, resemblance of

species of, 384
Euplsea midamus, 62, 79
E. rhadamanthus, 62
Euplcea, pale species of, in Moluccas

and New Guinea, 384
Eurylsemidae, sexual colouring and

nidification of, 126
Eustephanus, 324
Eustephanus galeritus, 326
Euterpe oleracea, 250
Evaporation and condensation, equal-
ising effects of, 229
Extinct animals, intermediate forms

of, 164
Extinction of lower races, 177

FEMALE birds, colours of, 80

sometimes connected with their

mode of nidification, 124
more exposed to enemies than the

males, 130

greater brilliancy of some, 379
Female butterflies generally dull-
coloured, 137

Female insects, mimicry by, 78, 137
colours of, 80

greater brilliancy of some, 372
Female sex, has no incapacity for as
brilliant coloration as the male, 129
in some groups requires more
protection than the male, 136
Ferns, 253

Fiji islands, pale butterflies of, 385

Fire-ants, 280

Fishes, protective colouring of, 41

causes of general coloration of,

348

Fissirostral birds, nests of, 123
Florida, ancient shell-mounds of, 436
Flowers, causes of colour in, 89

comparative scarcity of, in equa-
torial forests, 263
and insects, 266
of temperate zones brilliantly

coloured, 343
comparatively scarce in tropical

forests, 344

attractive colours of, 400
fertilised by insects, 400
attractive odours of, 402
when sweet not conspicuously

coloured, 402

attractive grouping of, 403
Alpine, why so beautiful, 403
why allied species differ in beauty,

404
when wind-fertilised not coloured,

404

relation of colours of, to distribu-
tion, 405
and fruits, recent views as to

action of light on, 406
of Auckland and Campbell's isles,

bright coloured, 408
Flowering -trunks, probable cause of,

244

Flying-lizards, 303

Foliage, two chief types of, in tropical
forests, 243

colours of, 395
Foot of savages does not approach

that of apes, 423 (note)
Forbes, Edward, objections to his

theory of polarity, 13, 17
Force is probably all Will-force, 211
Forest-belt, cause of equatorial, 238
Forest-belts, temperate, 240
Forests, effect of, on rainfall and
drought, 231

devastation caused by destruction

of, 232

equatorial, 240
undergrowth of tropical, 243
Forest-tree, section of a Bomean, 242
formed from climbers, 242

INDEX

483

Forest-trees, characteristics of, in equa-
torial forests, 241
of low growth, 243
uses of equatorial, 245

Formica gigas, 279

Fossils found under old lava beds in
California, 444

Frogs and toads, 305

Frog, with bright colours uneatable, 351

Fruit-bats, 307

Fruits of equatorial forest-trees, 245
attractive colours of, 397
protective colours of, 398
greater antiquity of protected than
attractive, 400

GALAPAGOS, 8

colours of productions of, 342.
poor in flowers and insects, 406
visited by Darwin, 456
Galton, Mr., on range of intellectual

power, 191
Ganocephala, 164
Gardener, Dr., on a large water Boa,

305
Gastropacha querci, protective colour

and form of, 45
Gaudry, M., on fossil mammals of

Greece, 165
Geckos, 302
Geiger, on ancient perception of colour,

413
Geographical distribution, dependent

on geologic changes, 3

its agreement with law of intro-
duction of new species, 8
of allied species and groups, 10
Geological distribution analogous to

geographical, 11
Geology, facts proved by, 3, 6
Geranium pratense, G. pusillum, 404
Gibbons, 306
Ginger-worts, 253
Giraffe, how it acquired its long neck,

32
Glacial period, man in America

during, 439
Gladstone, Mr., on the colour-sense,

413

Glsea, autumnal colours of this genus, 45
Glow-worm, \ise of its light, 374
Goatsuckers remotely allied to owls,

123 (note)

Goliath cuckoo, 297
Gosse, Mr., on Jamaica humming-birds,
318, 321

on the pugnacity of humming-
birds, 319

on food of humming-birds, 321
Gould, Mr., on sexual plumage of
gray phalarope, 81

on incubation by male dotterell,

81
on the motions of humming-birds,

317

Grallina australis, 133
Grammatophyllums, 256
Green birds almost confined to the

tropics, 38
Green, why the most agreeable colour,

412
Grisebach, on cause of vivid colours of

arctic flowers, 407
Guilielma speciosa, 250
Gums from equatorial forest-trees, 245
Gunther, Dr., on arboreal snakes, 40

on colouring of snakes, 73
Gymnocerus cratosomoides, 67
G. capucinus, G. dulcissimus, 69
Gynecia dirce, 43

HABENARIA chlorantha, 402
Habits, often persistent when use of
them has ceased, 121

of children and savages analogous

to those of animals, 121
if persistent and imitative maybe

termed hereditary, 121
of humming-birds, 316
Hairy covering of Mammalia, use of,
194

absence of, in man remarkable,

195
the want of it felt by savages,

195
could not have been abolished by

natural selection, 196
Harpagus diodou, 75
Heat due to condensation of atmo-
spheric vapour, 227

changes colours, 357
Heiliplus, a hard genus of Curculion-

idee, 67

Heliconidse, the objects of mimicry,
55
their secretions, 66

2 12

484

INDEX

Heliconidae, not attacked by birds, 57
sometimes mimicked by other

Heliconidse, 61

Heliconiinae and Acraeinse, local re-
semblances of, 383
Helladotherium, 165
Hemiptera, protected by bad odour,

52
Herbert, Rev. W., on song of birds,

105
Herring-gull, change of nesting habits

in, 115
Hesthesis, Longicorns resembling ants,

69

Hipparion, 164
Hippotherium, 164
Hispidae, imitated by Longicorns, 65
Bolothurida;, 136
Homalocranium semicinctum, 72
Hooker, Sir J., on flowers of Auckland

isles, 408
Hornbills, 298

Horns of beetles, probable use of, 372
Houses of American and Malay races

contrasted, 100
Howling monkeys, 307
Humming-birds, number of, 312, 319
distinctness of, 312, 316
structure of, 313
colours and ornaments of, 314
descriptive names of, 316
motions and habits of, 316
display of ornaments by males, 320
food of, 320
nests of, 322

geographical distribution and vari-
ation of, 322
of Juan Fernandez, 324
influenced by varied conditions

in South America, 329
relations and affinities of, 330
sternum of, 332

feather-tracts of, 333

resemblance of swifts to, 333

nestlings of, 334

differences from sun-birds, 334
Huxley, Professor, on "Physical Basis
of Life," 207

on volition, 212
Hyaenictis, 165

Hybernia, wintry colours of this
genus, 45

ICTERID.S:, sexual colouring and nidi-

fication of, 127
Ichthyopterygia, 164
Iguanas, 303
Imitation, the effects of, in man's

works, 99
Increase, checks to, studied by

Darwin, 458
Indians, how they travel through

trackless forests, 95
Insects, protective colouring of, 41
mimicking species of other orders,

68
senses of, perhaps different from

ours, 92
wingless, 290
general observations on tropical,

291

Instinct, how it may be best studied,
91

definition of, 93

in many cases assumed without

proof, 94

if possessed by man, 94
supposed, of Indians, 95
supposed to. be shown in the
construction of birds' nests, 98
Intellect of savages compared with

that of animals, 192
Intellectual power, range of, in man,

191

Interference colours in animals, 358
Islands, influence of locality on colour

in, 384

Ithomia, mimicked by Leptalis, 59
I. ilerdina, mimicked by four
groups of Lepidoptera, 60

JACAMARS, 297

Jamaica swift altering position of

nest, 116
Jeitteles, Professor, on various forms

of nests of Hirundo urbica, 115
Jerdon, Mr., on incubation by males

in Turnix, 81
Juan Fernandez, humming-birds of,

324

KALLIMA inachis and Kallima para-
lekta, wonderful resemblance of, to
leaves, 43-48

Kerner on the unbidden guests of
plants, 466

INDEX

485

LABYRINTHODONTIA, 164, 165
Lakes as cases of imperfect adapta-
tion, 150
Lamarck's hypothesis very different

from the author's, 31
Land shells, experiments on resistance

to salt water, 469
Laniadse, sexual colouring and nidi-

fication of, 128
Larentia tripunctaria, 46
Law which has regulated the intro-
duction of new species, 3, 6

confirmed by geographical distri-
bution, 8
high organisation of ancient

animals consistent with, 11
of multiplication in geometrical

progression, 142
of limited populations, 142
of heredity, 142
of variation, 142
of change of physical conditions,

143

of the equilibrium of nature, 143
as opposed to continual inter-
ference, 144
Laycock, Dr. , on law of " unconscious

intelligence," 205
Leaf butterfly, appearance and habits

of, 43

Leaf-insects, 287
Leopoldinia major, 252
Lepidoptera, diurnal, 272
Leptalis, species of, mimic Heliconidse,
59

gain a protection thereby, 137
a good case of mimicry, 362
Leptena erastus, 382
Leroy, on nest-building, 108
Lester, Mr. J. M., on wood -dove

and robin, 40
Levaillant, on formation of a nest,

112
Life does not imply consciousness, 209

(note)

Light, theory of, as producing colours,
341

action of, on plants, 396
supposed direct action of, on
colours of flowers and fruits,
406

Limenitis misippus, 63
Linnet imitating African finch, 105

Lizards refusing certain moths and

caterpillars, 85
devouring bees, 85
in the tropics, 302
Local causes of colour-development,

382

Locustidae, adaptive colouring of, 46
Locusts, richly coloured tropical, 288
Longicorns, 289
Loosestrife, Darwin's researches on

fertilisation of, 465
Lophornis ornatus, very pugnacious,

380
Lord Howe's island, white rail in,

388
Lowne, Mr. B. T., on nest-building of

ring-doves in confinement, 110
Luminousness of some insects a pro-
tection, 51

MACAWS, 293

Madagascar, white-marked butterflies

of, 386

Madeira, wingless insects of, ex-
plained by Darwin, 470
Maine, ancient shell-mounds of, 435
Malacoderms, a protected group, 66
Male birds, origin of ornamental
plumage of, 374

which incubate, 379
Male humming- birds produce a shriller

sound, 381
Males, theory of display of ornaments

by, 375

Malthus, Essay on Population, 20
Maluridje, 134
Malva sylvestris, M. rotundifolia,

404

Mammalia, supposed variations of,
comparable to those of butterflies,
386
local resemblances of, in Africa,

387
Mammals, mimicry among, 76

in the tropics, 306

Man, does he build by reason or imi-
tation, 99

his works mainly imitative, 113
antiquity of, 167, 180
difference of opinion as to his

origin, 167

unity or plurality of species, 168
persistence of type of, 169

486

INDEX.

Man, importance of mental and moral

characters, 173

his dignity and supremacy, 181
his influence on nature, 182
his future development, 182
range of intellectual power in, 191
rudiments of all the higher facul-
ties in savage, 192
his feet and hands, difficulties on
the theory of natural selection,
197

his voice, 198
his mental faculties, 198
difficulty as to the origin of the

moral sense in, 199
development of, probably directed
by a superior intelligence, 204
antiquity and origin of, 416
indications of extreme antiquity

of, 420
highly developed at very early

period, 421

antiquity of intellectual, 424
antiquity of, in North America,

433
in America coeval with extinct

mammalia, 438
in America in the glacial period,

439

fossil remains of, in the auri-
ferous gravels of California, 446
concluding remarks on antiquity

of, 448

Mantidae, adaptive colouring of, 46
mimicking white ants, 70
tropical forms of, 286
Mantis resembling an orchis -flower,

349

Mangroves, 262
Manicaria saccifera, 249
Marantaceae, 254
Marmosets, 307

Marshall, Messrs., on barbets, 297
Martins, Mr. Charles, on increased

size of leaves of arctic plants, 407
Mates readily found by birds, 370
Matter, the nature of, 207
Mr. Bayma on, 208
is force, 210
Mauritia, palm, 248
Maximiliana regia, 249
Mechanitis and Methona, mimicked
by Leptalis, 59

Mecocerus gazella, 67

Megapodidae, sexual colouring and

nidification of, 128
Meiglyptes, 332
Meldola, Mr. R., on variable colouring "

n insects, 347

Meliphagidas in Auckland isles prob-
ably flower-fertilisers, 408
Mesembryanthemum, stone, 396
Meteorological phenomena, intensity

of, at the equator, 234
Midas dives, 69
Mimeta, mimicking Tropidorhynchus,

73

Mimicry, meaning of the word, 54
theory of, 55
among Lepidoptera, 55
how it acts as a protection, 57
of other insects by Lepidoptera,

64

among beetles, 65
of other insects by beetles, 68
of insects by species of other

orders, 69

among the vertebrata, 70
among snakes, 72
among tree-frogs, 73
among birds, 73
among mammals, 76
objections to the theory of, 76
by female insects, 78
never occurs in the male only,

137

theory of, 362
Mimosa pudica, 262
Mivart, Professor, on animal origin of
man, 419

on the divergent affinities of man

and apes, 422
Momotidae, sexual colouring and

nidification of, 125

Mongredien, Mr., on showy and fra-
grant flowers, 402
Monkeys and pigeons, 295

abundance of, in the tropics, 306
Moral sense, difficulty as to the

origin of, 199

Morphos, how protected, 53
Moseley, Mr., on humming-birds of

Juan Fernandez, 327
Moths and conspicuously coloured

caterpillars, uneatable, 351
Motmots, 297

INDEX

487

Mott, Mr. Albert, on antiquity of in-
tellectual man, 425
Mound-builders, a semi-civilised race,

426
Mounds of N. America, antiquity of,

428
Miiller, Dr. Hermann, on fertilisation

of Alpine flowers, 403

on fertilisation of Martagon lily,

402
on differences of allied species of

flowers, 404
Murray, Mr. Andrew, objections to

theory of mimicry, 76
Musa paradisiaca, 254
Musaceae, 254
Muscicapidae, sexual colouring and

nidification of, 128
Musophagidae, sexual colouring and

nidification of, 125
Mygale, a bird-catching spider, 291
Mysis chameleon, changes of colour

of, 347

NAPEOGENES, all the species are

mimickers, 61

Natchez man, antiquity of, 438
Natural History before Darwin, 451
selection, the principle stated, 31,

32
general acceptance of the theory

of, 35

tabular demonstration of, 166
outline of theory of, 167
its effects on man and animals

different, 173
hardly acts among civilised

societies, 185
what it can not do, 187
cannot produce injurious or use-
less modifications, 187
Nectarineidae, 134

Necydalidae, mimic Hymenoptera, 68
Nemophas grayi, a Longicorn mi-
micked by a Longicorn, 68
Nests of birds, why different, 101
of young birds, how built, 104
inferior, built by young birds, 108
construction of, described by

Levaillant, 112
imperfections in, 116
influenced by changed conditions
and persistent habits, 119

Nests of birds, classification of, accord-
ing to function, 122
of humming-birds, 322

New forms, how produced by variation
and selection, 156

Newton, Professor, on appearance of
living humming-birds, 317

New Zealand, poor in flowers and
insects, 406

Nocturnal animals, colours of, 38

Nomada, 70

North America, antiquity of man in,
433

North American earth-works, 425

Nuttall, Mr., on the rufous flame-
bearer, 317

Nymphalidae, local resemblances of
species of distinct genera of, 383

OBEREA, species resemble Tenthre-
dinidse, 68

Oceanic islands first defined by
Darwin, 469

Odontocera odyneroides, 68

Odontocheila, 69

Odontomachus, genus of ants, 280

Odours absorbed unequally by dif-
ferently coloured stuffs, 390
of flowers attractive, 402

Odynerus sinuatus,64

OZcodoma cephalotes, 282

CEcophylla smaragdina, 279

Ogle, Dr. on colour and sense-percep-
tion, 389

Oil from palms, 252

Oncidiums, 257

Onthophilus sulcatus, like a seed, 42

Onychocerus scorpio, resembles bark,
41

Optical theory of colour, 354

Orange-tip butterfly, protective colour-
ing of, 43

Orchids, 255

Orchis, structure of an, explained by
natural selection, 146

Orgyia antiqua and O. gonostigma,
autumnal colours of, 45

Oriolidaa, 133

Ornamental humming-birds, the most
pugnacious, 380

Ornaments, display of, by male hum-
ming-birds, 320

Orthoptera, 286

488

INDEX

Oxyrhopus petolarius, 0. trigeminus,

0. formosus, 72
Owen, Professor, on more generalised

structure of extinct animals, 164

PACHTOTBIS fabricii, 69
Pachyrhynchi, weevils mimicked by

Longicorns, 67
Paeciloderma terminale, 66
Palaeolithic implements in North

America, 441
Paleotherium, 165

Palm-trees, uses and products of, 250-
253

wine, 250
Palms, 248

height of, 248
climbing, 249
Paloplotherium, 164
Pandanaceae, 255

Papilio, black and red group imitated,
60
pale varieties of, in Moluccas

and New Guinea, 384
Papilio nireus, changes of colour of

pupa of, 345
Papilionidae and Nymphalidae, local

resemblances of, 382
Paridse, sexual colouring and nidifica-

tion of, 126
Parrots, 293

red in Moluccas and New Guinea,

389

black in New Guinea and Mada-
gascar, 389

Passenger pigeon, cause of its great
numbers, 25

Patent inventions, as illustrating

classification, 162

Pengelly, Mr., on glacial man, 442
Phacellocera batesii, mimics one of

the Anthribidre, 67
Phaethornithinas, 321
Phalaropus fulicarius, 81, 132
Phasmidse, imitate sticks and twigs, 46
females resembling leaves, 79
tropical forms of, 286-288
Pheasants, brilliant plumage of, in cold

countries, 342

Pheidole, genus of ants, 281
Philippine islands, metallic colours of

butterflies of, 385

Philippine islands, white-marked birds
of, 388

Phoenix sylvestris, 251

Phyllium, wonderful protective colour
and form of, 46

Phyllostoma, 308

Physalia, 136

Picariae, 296

Picidae, sexual colouring and nidifica-
tion of, 125

Pieridee and Lycaenidae, local resem-
blances of, 382

Pieris, females only imitating Heli-
conidae, 79

Pieris pyrrha, 80

Pigeons, 295

black in Australia and Mada-
gascar, 389

Pigs, white poisoned in Virginia, black
not, 389

on instincts of newly-born, 109

Pipes from N. American mounds, 427

Pipridae, sexual colouring and nidifica-
tion of, 127

PittidsB, 133

Plantain, 254

Plantain-eaters, 298

Plants, protective coloration in, 396

Platycerium, 253

Pliocerus equalis, P. elapoides, P.
euryzonus, 72

Plumage of tropical birds, 300
of humming-birds, 315

Polarity, Forbes' theory of, 13, 34

Polyalthea, tree with flowers on trunk,
244

Polygonum bistorta, P. aviculare, 404

Polyrachis, genus of ants, 279

Ponera clavata, terrible sting of, 280

Pontea rapse, changes of colour of
chrysalis of, 345

Population of species, law of, 23

does not permanently increase, 24
not determined by abundance of

offspring, 24
checks to, 24

difference in the case of cats and
rabbits explained, 26

Portraits on sculptured pipes from
mounds, 427

Prevision, a case of, 86

Primrose and cowslip, Darwin's dis-
coveries in, 464

INDEX

489

Prosthemadera in the Auckland isles,

408

Protection, various modes in which
animals obtain it, 50, 51, 136
greater need of, in female insects

and birds, 80

Protective colouring, theory of, 47
Protective colours, theory of, 360
Psittaci (Parrots), sexual colouring

and nidification of, 126
Psittacula diopthalma, sexual differ-
ence of colour of, 353
Pterosauria, 164
Pterylography, 332
Ptychoderes, 67
Pyramid, the great, 430

the great, indicates an earlier

civilisation, 431
Pythons, 304

BABBITS, why white-tailed, 368

Races of man, origin of, 178

Rainbow, how described by ancient
writers, 413

Rainfall at London and Batavia, dia-
gram of, 228

greatest recorded at Batavia, 235

Raphia tsedigera, 249

Rattan-palms, 249

Recognition, use of diversity of
colour as a means of, 154 (note)
aided by colour, 367

Redbreast and wood-pigeon, protective
colouring of, 40

Redstart, imitating notes of chaffinch
and blackcap, 105

Reed, Mr. , on humming-birds in Juan
Fernandez, 328

Reeks, Mr. Henry, on change of nest-
ing habits in the herring-gull, 115

Representative groups, 8

of trogons, butterflies, etc., 10

Reptiles, protective colouring of, 40
abundant in tropics, 301

Rhamphastidse, sexual colouring and
nidification of, 125

Rhamphococcyx, 297

Rhinoceros, ancestral types of, 165

Ring-doves building nests in confine-
ment, 110

River system, as illustrating self-
adaptation, 149

Rudimentary organs, 17

SALVIN, Mr. Osbert, on a case of bird
mimicry, 75

on the pugnacity of humming-
birds, 319, 380
Saturnia pavonia - minor, protective

colouring of larva of, 46
Sauba ant, 282
Sauropterygia, 164

Savages, why they become extinct,
177

undeveloped intellect of, 190, 192
intellect of, compared with that

of animals, 192, 193
protect their backs from rain, 196
Saxifraga longi folia, 404
S. cotyledon, S. oppositifolia, 404
Scansorial birds, nests of, 123
Scaphura, 70

Science, debt of, to Darwin, 450
Scopulipedes, brush-legged bees, 65
Scorpions, 291
Screw-pines, 255 •
Scudder, Mr., on fossil insects, 165
Scutelleridae, mimicked by Longicorns,

69

Scythrops, 297

Seedling plants, Darwin's observa-
tions on, 467
Seeds, how protected, 399

vitality of, in salt water deter-
mined by Darwin, 469
experiments on transmission of,

by birds, 469
Sensitive -plants, 262
Sesia bombilif'ormis, 64
Sesiidae, mimic Hymenoptera, 64
Sexes, comparative importance of, in
different classes of animals, 78
of butterflies differently coloured

for recognition, 367
Sexual colours, 352
theory of, 364

Sexual selection, its normal action to
develop colour in both sexes, 129
among birds, 154
not a cause of colour, 369
neutralised by natural selection,

378

Shell-mounds, ancient, in Maine, 435
ancient, in Florida, 436
ancient, on Lower Mississippi, 436
ancient, at San Pablo, California,
436

490

INDEX

Shell-mounds, ancient, in the Aleutian
islands, 437

Shufeldt, Dr., on affinity of goat-
suckers and owls, 123 (note)

Sickle-bill humming-bird, 321

Sidgwick, Mr. A., on protective
colouring of moths, 46

Simocyonidae, 165

Sitta, sexual colouring and nidification
of, 126

Sittella, sexual colouring and nidifica-
tion of, 126

Size, correspondence of in tropical
flowers and insects', 406

Skull, the Calaveras, 447

Sky, colour of not mentioned in oldest
books, 413

Smith, Mr. Worth ington, on mimicry
in fungi, 397

Smyth, Professor Piazzi, on the Great
Pyramid, 430

Snakes, mimicry among, 72

characteristics of tropical, 304

Sobralias, 256

Soil, heat of, 222

influence of temperature on cli-
mate, 223

Solenopsis, genus of ants, 281

Song of birds, instinctive or imitative,
104

Sorby, Mr., on composition of chloro-
phyll, 395

Spalding, on instinctive actions of
young birds, 109

Sparrow learning song of linnet and
goldfinch, 105

Species, law of population of, 23

abundance or rarity of, dependent
on the adaptation to conditions,
26
diversity of opinions as to, 454

Speed of animals, limits of, 160

Sphecia craboniforme, 64

Sphecomorpha chalybea, 68

Sphegidaj, mimicked by flies, 69

Spices from equatorial forest - trees,
245

Spiders, which mimic ants and flower
buds, 70

remarkable tropical, 291

Spilosoma menthastri, 63

Spruce, Dr. Richard, on habits of
Indians of Peru, 107

Spruce, Dr., on number of ferns at
Tarapoto, 253

on inconspicuousness of tropical
flowers, 264

Stainton, Mr., on moths rejected by
turkeys, 56, 63

Stalachtis, a genus of Erycinidee, the
object of mimicry, 60

St. Helena, 9

Stick-insects, 287

Stinging insects generally conspicu-
nisly coloured, 52

St. John, Mr., on large python, 305

Stone mortars in auriferous gravels of
California, 445

Streptolabis hispoides, 66

Structure of humming-birds, 313

Struggle for existence, 23, 25

Sturnidae, sexual colouring and nidifi-
cation of, 127

Sturnopastor, 123

Sugar from palm-trees, 250

Sun-birds, differences from humming-
birds, 334

Sun's noonday altitude in Java and
London compared, 221

Sun's rays, heating effect of, 221

Sunrise in the equatorial zone, 233

Survival of the fittest, law of, stated,
26

its action in determining colour,
48

Swainson's circular and quinarian
theory, 34

Swallows, various forms of nests of,
114

Swifts, resemblances of to humming-
birds, 333

and humming-birds, Dr. Shu-
feldt on supposed affinities of,
337 (note)

Sylviadae, sexual colouring and nidifi-
cation of, 128

Symmachia trochilus, 274
colubris, 275

Synapta, 136

TACHORNIS phaenicobea, 116
Tanagridse, sexual colouring and nidi-
fication of, 127
Tapir, ancestral types of, 165
Telephori, similar colouring of two
i sexes, 80

INDEX

491

Temperate and cold climates favour-
able to civilisation, 177
Temperature of London and Batavia
compared, 221

of different latitudes, various

causes of, 221

influenced by heat of soil, 222
influenced by aqueous vapour of

atmosphere, 223
of tropical and temperate zones,

cause of illustrated, 226
Tertiary gravels of Colorado, stone

implements in, 448
Thaumastura cora, very pugnacious,

381

Thecodontia, 164
Therates, mimicked by Heteromera,

67

Tiger, adaptive colouring of, 39
Times newspaper on natural selection,

162
Timor and Flores, white-marked birds

of, 388

Timor and Scotland, climates com-
pared, 227

Tools, importance of, to man, 174
Toucans, 298
Tree-frogs, probable mimicry by, 73

abundance of, in the tropics, 305
Tricondyla, mimicked by cricket, 69
Tristram, Rev. H., on colours of

desert animals, 37
Trochilida;, 313
Trochilium tipuliforme, 64
Trogonidae, sexual colouring and nidi-

fication of, 125
Trogons, 297

Tropical birds often green, 38
Tropical vegetation, concluding re-
marks on, 267

probable causes of its luxuriance

and variety, 268
Mr. Belt on, 268
birds, coloration of, 300
green, 300
dull-coloured, 301

Tropics, most favourable to production
of perfect adaptation among ani-
mals, 49
not favourable to growth of

civilisation, 177
limitation of, 218
aspects of animal life in, 309

Tropidorhynchus mimicked by orioles,

Trunks, variety of, 241-243

probable cause of flowering, 244
Truthfulness of some savages, 200
not to be explained on utilitarian

hypothesis, 201
Turdidse, sexual colouring and nidifi-

cation of, 128
Turnix, 81, 132
Twilight, short at equator, 232
Tyndall, Professor, on origin of con-
sciousness, 206
Typical colours, 374

UPUPID.E, sexual colouring and nidifi-

cation of, 125

Useful and useless variations, 27
Utility, importance of the principle of,

35, 89

VAMPIRE-BATS, 308

Vanda lowii, 257

Variation, how influenced, 326

studied by Darwin, 457, 460, 462
Variations, useful and useless, 27

laws of, 142

universality of, 156, 150

are there limits to, 159

of domestic dogs, 160

of pigeons, 160

Varieties, instability of, supposed to
prove the permanent distinctness of
species, 21

if superior will extirpate original

its reversion then impossible, 29
of domesticated animals may

partially revert, 29, 30
Vegetation, equatorial, 238
Vertebrata, mimicry among, 70
Vipers, green, 304

Vitality a cause of bright colour, 365
Voice of man, not explained by

natural selection, 198
Volucella, species of mimic bees, 54,
70

WARNING COLOURS, theory of, 361
Wasps and bees, 286
Wave-lengths of coloured rays, 355
Weale, Mr. J. P. Mansel, on plants of
Karoo, 397

115472

492

INDEX

Weale, Mr. J. P. Mansel, on Ajuga

ophrydis, 397
Weapons and tools, how they affect

man's progress, 174
Webber, Mr., on food of humming-
birds, 321
Weevils often resemble small lumps

of earth, 42

Weir, Mr. Jenner, on a moth refused
by birds, 63

on beetles refused by birds, 66
on caterpillars eaten, and rejected

by birds, 84

West Indian islands, large and bril-
liant butterflies of, 386

peculiarly coloured birds of, 387
Westwood, Professor, objections to

theory of mimicry, 76
Whip-snakes, 304
White animals poisoned where black

escape, 389

White colour in domesticated and
wild animals, 48

in animals, how produced, 359

(note)
doubly prejudicial to animals,

390

White colours influencing sense-per-
ception, 389
White tropical birds, 301

Whitney, Professor, on the Calaveras

skull, 447

Wild and domesticated animals, essen-
tial differences of, 30, 31
Will really exerts force, 211

probably the primary source of

force, 212
Wilson, Dr., on pottery from North

American mounds, 427
Winds, influence of, on temperature,

225

direction of, near equator, 225
cause of cold near equator, 226
Wood, Mr. T. W., on orange-tip

butterfly, 43
Woodcocks and Snipes, protective

colouring of, 39
Woodpeckers, why scarce in England,

25
Woods from equatorial forest-trees,

245
Works of art in auriferous gravels of

California, 445

XANTHIA, autumnal colours of these
moths, 45

ZEBRA, possible use of its stripes, 368
Zebras, 164
Zingiberaceae, 254

THE END

Printed by R. & R. CLARK, Edinburgh.