COLOURATION

IMALS

\

COLOURATION

IN

ANIMALS AND PLANTS.

BY THE LATE

ALFRED TYLOR, F.G.S.

Edited by •

SYDNEY B. J. SKERTCHLY, F.G.S.,

LATE OF H.M. GEOLOGICAL SURVEY.

LONDON:
FEINTED BY ALABASTER, PASSMOKE, AND SONS,

FANN STREET, ALDERSGATE STREET, B.C.
1886.

IN MEMOEY

OF A FBiENDSHIP OF MANY YEABS,

THIS BOOK

is
Sffectionatdg EnscrflbrtJ

TO

THE EIGHT HON. GEORGE YOUNG, P.O.
1885.

2091097

PREFACE.

rPHIS little book is only a sketch of what its Author desired it to be,
and he never saw the completed manuscript. Beginning with the
fundamental idea that decoration is based upon structure, he saw that
this was due to the fact that in the lower, transparent, animals, colour
is applied directly to the organs, and that the decoration of opaque
animals is carried out on the same principle — the primitive idea being
maintained. Where function changes the pattern alters, where
function is localized colour is concentrated : and thus the law of
emphasis was evolved. Symmetry was a necessary consequence, for
like parts were decorated alike, and this symmetry was carried out in
detail apparently for the sake of beauty, as in the spiracular markings
of many larvae. Hence the reason for recognizing the law of
repetition.

With the developing of these ideas the necessity for recognizing
some sort of consciousness even in the lowest forms of life was forced
upon the Author, until inherited memory formed part of his scientific
faith. This he saw dimly years ago, but only clearly when Mr. S.
Butler's remarkable " Life and Habit " appeared, and he was gratified
and strengthened when he found Mr. Romanes adopting that theory
in his " Mental Evolution."

The opening chapters are designedly elementary ; for the Author had
a wise dread of locking intellectual treasures in those unpickable
scientific safes of which " the learned " alone hold keys.

Only a very small portion of the vast array of facts accumulated has
been made use of, and the Author was steadily working through the

vi PREFACE.

animal kingdom, seeking exceptions to his laws, but finding none, when
death closed his patient and far-seeing eyes. A few days before the
end he begged me to finish this abstract, for I had been at his side
through all his labours.

The work contains his views as clearly as I could express them,
though on every page I feel they suffer from want of amplification.
But I feared the work might become the expression of my own thoughts,
though want of leisure would probably have prevented that unhappy
result. Now it is finished, I would fain write it all over again, for
methinks between the lines can be seen gleams of brighter light.

CJ O O

SYDNEY B. J. SKERTCHLY.

CAKSIIALTON,

July llth, 1886.

' .' The coloured illustrations were drawn by Mrs. Skertchly chiefly from nature,
and very carefully printed by Messrs. Alabaster, Passuiore, and Sons.

CONTENTS.

CHAPTEE PAGE

I. INTRODUCTORY 1

II. INHERITED MEMORY ..." 8

III. INTRODUCTORY SKETCH . ' 16

IV. COLOUR, ITS NATURE AND RECOGNITION 25

V. THE COLOUR SENSE 32

VI. SPOTS AND STRIPES 39

VII. COLOURATION IN THE INVERTEBRATA 49

VIII. DETAILS OF PROTOZOA . 56

IX. DETAILS OF CCELENTERATA 59

X. THE COLOURATION OF INSECTS 68

XI. THE COLOURATION OF INSECTS 75

XII. ARACHNIDA • 82

XIII. COLOURATION OF INVERTEBRATA . , • - V . . . . 85

XIV. COLOURATION OF VERTEBRATA 88

XV. THE COLOURATION OF PLANTS ....... 95

XVI. CONCLUSIONS . 97

LIST OF WOODCUTS.

Fig. 1. Part of Secondary Feather of Argus Pheasant.

Fig. 2. Ditto Wing-feather of ditto.

Fig. 3. Diagram of Butterfly's Wing.

Fig. 4. Python.

Fig. 5. Tiger's Skin.

Fig. 6. Ditto.

Fig. 7. Tiger's Head, side view.

Fig. 8. Ditto, crown.

Fig. 9. Leopard's Skin.

Fig. 10. Ditto.

Fig. 11. Leopard's Head, side view.

Fig. 12. Ditto, crown.

Fig. 13. Lynx' Skin.

Fig. 14. Ditto.

Fig. 15. Ocelot.

Fig. 16. Badger.

Fig. 17. Begonia Leaf.

DESCRIPTION OF PLATES.

PLATE I. Kallima Inachus, the Indian Leaf Butterfly.
p. 28. Fig. 1 . With wings expanded.

Fig. 2. Two Butterflies at rest, showing their exact resemblance

to dead leaves.
This insect affords one of the best examples of protective resemblance.

PLATE II. Illustration of mimicry in butterflies.
p. 30. Fig. 1. Male of Papilio merope.

Fig. 2. Female of ditto mimicking Fig. 3.
Fig. 3. Danais niavius.

On the African continent both species occur, but in Madagascar D.
niavius is wanting, and the female P. merope is coloured like the male.

PLATE III. Fig. 1. Oonepteryx Cleopatra,
p. 40. Fig. 2. Gonepteryx rhamni, male.

Note.— The orange spot in Fig. 2 has spread over the
wing in Fig. 1 .

Fig. 3. Vanessa Antiopa.
Fig. 4. Panopcea hirta.
Fig. 5. Acrea gea.

These two last belong to widely different genera, but are admirable
examples of mimicry.

PLATE IV. Fig. 1. Leucophasia Sinapis.

p. 42. Fig. 2. Ditto, var. diniensis.

Fig. 3. Anthocaris cardamines, male.

Fig. 4. Ditto, female.

Fig. 5. Anthocaris belemia.

xii DESCRIPTION OF PLATES.

PLATE IV. Fig. 6. Anthocaris belia.
contd. Fig. 7. Ditto, var. simplonia.

Fig. 8. Anthocaris eupheno, female.
Fig. 9. Ditto, male.

Fig. 10. Anthocaris euphemoides.

Fig. 11. Papilio machaon.

Fig. 12. Papilio podalirius.

Fig. 13. Pieris napi, summer form.
Fig. 14. Ditto, winter form.
Fig. 15. Ditto, var. bryoniai (alpine form).
Fig. 16. Ditto, summer form, underside.
Fig. 17. Ditto, winter form, underside.
Fig. 18. Ditto, var. Iryonice, underside.

Figs. 13-18 illustrate admirably the variations of the yeUow and black
in the same species.

PLATE V. Fig. 1. Araschnia prorsa, male.
p. 44. Fig. 2. Ditto, female.

Fig. 3. Araschnia levana, female.
Fig. 4. Ditto, male.

Fig. 5. Parayra aiyeria.

Fig. 6. Araschnia porima.
Fig. 7. Ditto, var. meione.

Fig. 8. Grapta interrogation's.
Fig. 9. Ditto.

Fig. 10. Ditto.

Fig. 11. Papilio Ajax, var. Walshii.
Fig. 12. Ditto, var. telamonidcs.

Fig. 13. Ditto, var. Marcellus.

Figs. 1-5 are all one species ; levana being the winter form, prorsa the
summer form, and porima intermediate. Similiarly 6-7 are the same
species, meione being the southern form. So with 8-9 and 11-13, which
are only seasonal varieties. Here we can actually trace the way in which
varieties are formed. See Weismann's work, cited in the text.

PLATE VI. Syncoryne pnlchella, magnified. After Professor Allman. Gymno-
p. 62. blastic or Tubularian Hydroids. Kay Soc., 1871, pi. vi., figs. 1

and 3.
Fig. 1. A planoblast as seen passively floating in the water after

liberation.
Fig. 2. The entire hydrosoma of syncoryne.

a. The spadix.

b. The medusso or planoblasts in various stages of develop-

ment.

DESCRIPTION OF PLATES. Xlll

PLATE VII.

p. 80. Fig. 1. Deilephila galii, immature.

Fig. 2. Ditto brown variety, adult.

Fig. 3. Deilephila euphorbice.

Fig. 4. Sphinx ligustri.

Fig. 5. Deilephila euphorbice, dorsal view.

Fig. 6. Orgyia antiqua.

Fig. 7. Abraxas grossulariata.

Fig. 8. Bombyx neustria.

Fig. 9. Callimorpha dominula.

Fig. 10. Euchelia jacobcea.

Fig. 11. Papilio machaon.

SPIDERS.

PLATE VIII. Fig. 1.
p. 84. Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.
Fig. 7.
Fig. 8.
Fig. 9.

Fig. 10.
Fig. 11.
Fig. 12.
Fig. 13.
Fig. 14.
Fig. 15.
Fig. 16.

T7itr 1 7

Segestria senoculata, female.
Sparassus smaragdulus, male.
Lycosa piscatoria, female.

allodroma, male.

allodroma, female.
Diagram of Lycosa, showing form and position of vessels.
After Gegenbaur.
Lycosa campestris, female.
Thomisus luctuosus, male.
Salticus scenicus, female.
Lycosa rapax, female.

Theridion pictum, female.
Lycosa picta, female.

All the above are British species, and copied from Blackwell's " Spiders
of Great Britain and Ireland." Eay Soc., 1862.

FISHES.

PLATE IX. Fig. 1. Windermere Char. Salmo Willughbii. A species peculiar
p. 88. to our North of England lakes.

Fig. 2. Perch, Perca fluviatilis, showing the modified rib-like
markings.

SUNBIRDS.

PLATE X. Fig. 1. Nectarinea chloropygia.
p. 90. Fig. 2. Nectarinea christince.

These birds illustrate regional colouration well.

xiv DESCRIPTION OF PLATES.

LEAVES.

PLATE XI. Fig. 1. Horse Chestnut, JEschulus hippocastanum, decaying.

p. 95. Fig. 2. Coleus.

Fig. 3. Begonia rex.

Fig. 4. Begonia.

Fig. 5. Caladium bicolor.

Fig. 6. Ancechtochilus xanthophyllus.

FLOWERS.

PLATE XII. Fig. 1. Gloxinia, with 5 petals, showing uneven colouring.
p. 96. Fig. 2. Gloxinia, with 6 petals, showing regular colouring.

Figs. 3 and 4. Pelargoniums, showing the variation of the dark
markings with the different sized petals.

COLOURATION IN ANIMALS AND PLANTS.

CHAPTER I.

INTRODUCTION,

BEFORE Darwin published his remarkable and memorable work
on the Origin of Species, the decoration of animals and plants
was a mystery as much hidden to the majority as the beauty of the
rainbow ere Newton analysed the light. That the world teemed
with beauty in form and colour was all we knew ; and the only guess
that could be made as to its uses was the vague and unsatisfactory
suggestion that it was appointed for the delight of man.

Why, if such was the case, so many flowers were " born to blush
unseen," so many insects hidden in untrodden forests, so many
bright-robed creatures buried in the depths of the sea, no man could
tell. It seemed but a poor display of creative intelligence to
lavish for thousands of years upon heedless savage eyes such glories
as are displayed by the forests of Brazil; and the mind recoiled
from the suggestion that such could ever have been the prime
intention.

But with the dawn of the new scientific faith, light began to shine
upon these and kindred questions ; nature ceased to appear a mass
of useless, unconnected facts, and ornamentation appeared in its true
guise as of extreme importance to the beings possessing it. It was
the theory of descent with modification that threw this light upon
nature.

This theory, reduced to its simplest terms, is that species, past
and present, have arisen from the accumulation by inheritance of
minute differences of form, structure, colour, or habit, giving to the

2 Colouration in Animals and Plants.

individual a better chance, in the struggle for existence, of obtaining
food or avoiding danger. It is based on a few well-known and
universally admitted facts or laws of nature : namely, the law of
multiplication in geometrical progression causing the birth of many
more individuals than can survive, leading necessarily to the struggle
for existence ; the law of heredity, in virtue of which the offspring
resembles its parents ; the law of variation, in virtue of which the
offspring has an individual character slightly differing from its
parents.

To illustrate these laws roughly we will take the case of a bird,
say, the thrush. The female lays on the average five eggs, and if all
these are hatched, and the young survive, thrushes would be as seven
to two times as numerous in the next year. Let two of these be
females, and bring up each five young ; in the second year we shall
have seventeen thrushes, in the third thirty-seven, in the fourth
seventy-seven, and so on. Now common experience tells us not
merely that such a vast increase of individuals does not take place,
but can never do so, as in a very few years the numbers would
be so enormously increased that food would be exhausted.

On the other hand, we know that the numbers of individuals
remain practically the same. It follows, then, that of every five
eggs four fail to arrive at maturity ; and this rigorous destruction of
individuals is what is known as the struggle for existence. If, instead
of a bird, we took an insect, laying hundreds of eggs, a fish, laying
thousands, or a plant, producing still greater quantities of seed, we
should find the extermination just as rigorous, and the numbers of
individuals destroyed incomparably greater. Darwin has calculated
that from a single pair of elephants nearly nineteen millions would
be alive in 750 years if each elephant born arrived at maturity, lived
a hundred years, and produced six young — and the elephant is the
slowest breeder of all animals.

The struggle for existence, then, is a real and potent fact, and
it follows that if, from any cause whatever, a being possesses any
power or peculiarity that will give it a better chance of survival
over its fellows — be that power ever so slight— it will have a very
decided advantage.

Now it can be shown that no two individuals are exactly alike,
in other words, that variation is constantly taking place, and that
no animal or plant preserves its characters unmodified. This we
might have expected if we attentively consider how impossible it

Introduction. 3

is for any two individuals to be subjected to exactly the same
conditions of life and habit. But for the proofs of variability we
have not to rely upon theoretical reasoning. No one can study,
even superficially, any class or species without daily experiencing
the conviction that no two individuals are alike, and that variation
takes place in almost every conceivable direction.

Granted then the existence of the struggle for existence and
the variability of individuals, and granting also that if any varia-
tion gives its possessor a firmer hold upon life, it follows as a
necessity that the most favoured individuals will have the best
chance of surviving and leaving descendants, and by the law of
heredity, we know these offspring will tend to inherit the charac-
ters of their parents. This action is often spoken of as the
preservation of favoured races, and as the survival of the fittest.

The gradual accumulation of beneficial characters will give
rise in time to new varieties and species ; and in this way primarily
has arisen the wonderful diversity of life that now exists. Such, in
barest outline, is the theory of descent with modification.

Let us now see in what way this theory has been applied to
colouration. The colours, or, more strictly, the arrangement of
colours, in patterns is of several kinds, viz. : —

1. General Colouration, or such as appears to have no very
special function as colour. We find this most frequently in the
vegetable kingdom, as, for instance, the green hue of leaves, which,
though it has a most valuable function chemically has no particular
use as colour, so far as we can see.

2. Distinctive Colouration, or the arrangement of colours in
different patterns or tints corresponding to each species. This is
the most usual style of colouring, and the three following kinds
are modifications of it. It is this which gives each species its own
design, whether in animals or plants.

3. Protective Resemblance, or the system of colouring which
conceals the animal from its prey, or hides the prey from its foe.
Of this class are the green hues of many caterpillars, the brown
tints of desert birds, and the more remarkable resemblances of
insects to sticks and leaves.

4. Mimetic Colouration, or the resemblance of one animal to
another. It is always the resemblance of a rare species, which is
the favourite food of some creature, to a common species nauseous
to the mimicker's foe. Of this character are many butterflies.

c

4 Colouration in Animals and Plants.

5. Warning Colours, or distinctive markings and tints rendering
an animal conspicuous, and, as it were, proclaiming noli me tangere
to its would-be attackers.

6. Sexual Colours, or particular modifications of colour in the two
sexes, generally taking the form of brilliancy in the male, as in the
peacock and birds of paradise.

Under one or other of these headings most schemes of coloura-
tion will be found to arrange themselves.

At the outset, and confining ourselves to the animal kingdom
for the present, bearing in mind the fierce intensity of the struggle
for life, it would seem that any scheme of colour that would enable
its possessor to elude its foes or conceal itself from its prey, would
be of vital importance. Hence Ave might infer that protective
colouring would be a very usual phenomenon ; and such we find to
be the case. In the sea we have innumerable instances of protec-
tive colouring. Fishes that lie upon the sandy bottom are sand-
coloured, like soles and plaice, in other orders we find the same
hues in shrimps and crabs, and a common species on our shores
(Carcinu* mwnas) has, just behind the eyes, a little light irregular
patch, so like the shell fragments around that when it hides in the
sand, with eyes and light spot alone showing, it is impossible to
distinguish it.

The land teems with protective colours. The sombre tints of so
many insects, birds and animals are cases in point, as are the
golden coat of the spider that lurks in the buttercup, and the green
mottlings of the underwings of the orange-tip butterfly. Where
absolute hiding is impossible, as on the African desert, we
find every bird and insect, without exception, assimilating the
colour of the sand.

But if protective colour is thus abundant, it is no less true that
colour of the most vivid description has arisen for the sole purpose
of attracting notice. We observe this in the hues of many butter-
flies, in the gem-like humming birds, in sun-birds, birds of paradise,
peacocks and pheasants. To see the shining metallic blue of a
Brazilian Morpho flashing in the sun, as it lazily floats along the
forest glades, is to be sure that in such cases the object of the insect
is to attract notice.

These brilliant hues, when studied, appear to foil into two
i: asses, having very diverse functions, namely Sexual and Warning
Colours.

Introduction. 5

Protection is ensured in many ways, and among insects one of
the commonest has been the acquisition of a nauseous flavour.
This is often apparent even to our grosser senses ; and the young
naturalist who captures his first crimson-and-green Burnet Moth or
Scarlet Tiger, becomes at once aware of the existence of a fetid
greasy secretion. This the insectivorous birds know so well that
not one will ever eat such insects. But unless there were some
outward and visible sign of this inward and sickening taste, it
would little avail the insect to be first killed and then rejected.
Hence these warning colours — they as effectively signal danger as
the red and green lamps on our railways.

It may here be remarked that wherever mimickry occurs in
insects, the species mimicked is always an uneatable one, and the
mimicker a palatable morsel. It is nature's way of writing " poison "
on her jam-pots.

The other class of prominent colours — the Sexual — have given
rise to two important theories, the one by Darwin, the counter-
theory by Wallace.

Darwin's theory of Sexual Selection is briefly this : — He points
out in much detail how the male is generally the most powerful,
the most aggressive, the most ardent, and therefore the wooer,
while the female is, as a rule, gentler, smaller, and is wooed or
courted. He brings forward an enormous mass of well-weighed
facts to show, for example, how often the males display their
plumes and beauties before their loves in the pairing season, and
his work is a long exposition of the truth that Tennyson proclaimed
when he wrote : —

" In the spring a fuller crimson comes upon the robin's breast,
In the spring the wanton lapwing gets himself another crest,
In the spring a livelier iris changes on the burnished dove,
In the spring the young man's fancy lightly turns to thoughts of love."

That birds are eminently capable of appreciating beauty is
certain, and numerous illustrations are familiar to everyone. Suffice
it here to notice the pretty Bower Birds of Australia, that adorn
their love arbours with bright shells and flowers, and show as
unmistakable a delight in them as the connoisseur among his art
treasures.

From these and kindred facts Darwin draws the conclusion
that the females are most charmed with, and select the most

(> Colouration in Animal* and Plants.

brilliant males, and that by continued selection of this character,
the sexual hues have been gradually evolved.

To this theory Wallace takes exception. Admitting, as all
must, the fact of sexually distinct ornamentation, he demurs to the
conclusion that they have been produced by sexual selection.

In the first place, he insists upon the absence of all proof
that the least attractive males fail to obtain partners, without
which the theory must fail. Next he tells us that it was the case
of the Argus pheasant, so admirably worked out by Darwin, that
first shook his faith in sexual selection. Is it possible, he asks,
that those exquisite eye-spots, shaded " like balls lying loose
within sockets " (objects of which the birds could have had no
possible experience) should have been produced ..." 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 " ? *

As an alternative explanation, he would advance no new theory,
but simply apply the known laws of evolution. He points out, and
dwells upon, the high importance of protection to the female while
bitting on the nest. In this way he accounts for the more sombre
hues of the female ; and finds strong support in the fact that in
those birds in which the male undertakes the household duties, he
is of a domestic dun colour, and his gad-about-spouse is bedizened
like a country-girl at fair time.

With regard to the brilliant hues themselves, he draws attention
to the fact that depth and intensity of colour are a sign of vigour
and health — that the pairing time is one of intense excitement, and
that we should naturally expect to find the brightest hues then
displayed. Moreover, he shows — and this is most important to us—
that " the most highly-coloured and most richly varied markings
occur on those parts which have undergone the greatest modifi-
cation, or have acquired the most abnormal development." f

It is not our object to discuss these rival views; but they are
here laid down in skeleton, that the nature of the problem of the
principles of colouration may be easily understood.

Seeing, then, how infinitely varied is colouration, and how
potently selection has modified it, the question may be asked, " Is

• Wallace, Tropical Nature, p. 206. f Op. cit., p. 206.

Introduction. 7

it possible to find any general system or law which has determined
the main plan of decoration, any system which underlies natural
selection, and through which it works " "? We venture to think there
is ; and the object of this work is to develop the laws we have
arrived at after several years of study.

CHAPTER II.

INHERITED MEMORY.

MANY of our observations seemed to suggest a quasi-intelligent
action on the part of the beings under examination ; and we
were led, early in the course of our studies, to adopt provisionally the
hypothesis that memory was inherited — that the whole was con-
sequently wiser than its parts, the species wiser than the individual,
the genus wiser than the species.

One illustration will suffice to show the possibility of memory
being inherited. Chickens, as a rule, are hatched with a full know-
ledge of how to pick up a living, only a few stupid ones having
to be taught by the mother the process of pecking. When eggs are
hatched artificially, ignorant as well as learned chicks are produced,
and the less intelligent, having no hen instructor, would infallibly
die in the midst of plenty. But if a tapping noise, like pecking, be
made near them, they hesitate awhile, and then take to their food
with avidity. Here the tapping noise seems certainly to have
awakened the ancestral memory which lay dormant.

It may be said all this is habit. But what is habit ? Is it any
explanation to say a creature performs a given action by habit ? or is
it not rather playing with a word which expresses a phenomenon
without explaining it ? Directly we bring memory into the field we
get a real explanation. A habit is acquired by repetition, and could
not. arise if the preceding experience were forgotten. Life is
largely made up of repetition, which involves the formation of
habits ; and. indeed, everyone's experience (habit again) shows that
life only runs smoothly when certain necessary habits have been
acquired so perfectly as to be performed without effort. A being at
maturity is a great storehouse of acquired habits; and of these many

Inherited Memory. 9

are so perfectly acquired, i.e., have been performed so frequently,
that the possessor is quite unconscious of possessing them.

Habit tends to become automatic ; indeed, a habit can hardly be
said to be formed until it is automatic. But habits are the result of
experience and repetition, that is, have arisen in the first instance by
some reasoning process; and reasoning implies consciousness. Never-
theless, the action once thought out, or reasoned upon, requires less
conscious effort on a second occasion, and still less on a third, and
so on, until the mere occurrence of given conditions is sufficient to
ensure immediate response without conscious effort, and the action
is performed mechanically or automatically : it is now a true habit.
Habit, then, commences in consciousness and ends in unconsciousness.
To say, therefore, when we see an action performed without
conscious thought, that consciousness has never had part in its
production, is as illogical as to say that because we read auto-
matically we can never have learned to read.

The thorough appreciation of this principle is absolutely essential
to the argument of this work ; for to inherited memory we attribute
not only the formation of habits and instincts, but also the modifica-
tion of organs, which leads to the formation of new species. In a
word, it is to memory we attribute the possibility of evolution, and
by it the struggle for existence is enabled to re-act upon the forms
of life, and produce the harmony we see in the organic world.

Our own investigations had led us very far in this direction ; but
we failed to grasp the entire truth until Mr. S. Butler's remarkable
work, " Life and Habit," came to our notice. This valuable contri-
bution to evolution smoothed away the whole of the difficulties we
had experienced, and enabled us to propound the views here set
forth with greater clearness than had been anticipated.

The great difficulty in Mr. Darwin's works is the fact that he
starts with variations ready made, without trying, as a rule, to
account for them, and then shows that if these varieties are benefi-
cial the possessor has a better chance in the great struggle for exist-
ence, and the accumulation of such variations will give rise to new
species. This is what he means by the title of his work, " The
Origin of Species by means of Natural Selection or the Preservation
of Favoured Races in the Struggle for Life." But this tells us
nothing whatever about the origin of species. As Butler puts it,
" Suppose that it is an advantage to a horse to have an especially
broad and hard hoof: then a horse born with such a hoof will, indeed,

10 Colouration in Animals and Plants.

probably survive in the struggle for existence ; but he was not born
with the larger and harder hoof because of his subsequently surviving.
He survived because he was born fit— not he was born fit because
he survived. The variation must arise first and be preserved
afterwards."*

Mr. Butler works out with admirable force the arguments, first,
that habitual action begets unconsciousness ; second, that there is a
unity of personality between parent and offspring ; tbird, that there
is a memory of the oft-repeated acts of past existences, and, lastly,
that there is a latency of that memory until it is re-kindled by the
presence of associated ideas.

As to the first point, we need say no more, for daily experience
confirms it ; but the other points must be dealt with more fully.

Mr. Butler argues for the absolute identity of the parent and off-
spring; and, indeed, this is a necessity. Personal identity is a
phrase, very convenient, it is true, but still only a provisional mode
of naming something we cannot define. In our own bodies we say
that our identity remains the same from birth to death, though we
know that our bodily particles are ever changing, that our habits,
thoughts, aspirations, even our features, change — that we are no
more really the same person than the ripple over a pebble in a brook
is the same from moment to moment, though its form remains. If
our personal identity thus elude our search in active life, it certainly
becomes no more tangible if we trace existence back into pre-natal
states. We are, in one sense, the same individual ; but, what is equally
important, we were part of our mother, as absolutely as her limbs are
part of her. There is no break of continuity between offspring and
parent — the river of life is a continuous stream. We judge of our
own identity by the continuity which we see and appreciate ; but
that greater continuity reaching backwards beyond the womb to the
origin of life itself is no less a fact which should be constantly kept
in view. The individual, in reality, never dies ; for the lamp of life
never goes out.

For a full exposition of this problem, Mr. Butler's " Life and
Habit " must be consulted, where the reader will find it treated in
a masterly way.

This point was very early appreciated in our work; and in a
paper read before the Anthropological Institute f in the year 1879,

• Evolution, Old and New, p. 346.

t On a New Method of Expressing the Law of Specific Change. By A. Tylor.

Inherited Memory. 11

but not published, this continuity was insisted upon by means of
diagrams, both of animal and plant life, and its connection with here-
dity was clearly shown, though its relation to memory was only dimly
seen. From this paper the following passage may be quoted : " If, as
I believe, the origin of form and decoration is due to a process similar
to the visualising of object-thoughts in the human mind, the power
of this visualising must commence with the life of the being. It
would seem that this power may be best understood by a correct
insight into biological development. It has always excited wonder
that a child, a separate individual, should inherit and reproduce the
characters of its parents, and, indeed, of its ancestors ; and the
tendency of modern scientific writing is often to make this obscure
subject still darker. But if we remember that the great law of all
living matter is, that the child is not a separate individual, but a
part of the living body of the parent, up to a certain date, when it
assumes a separate existence, then we can comprehend how living
beings inherit ancestral characters, for they are parts of one con-
tinuous series in which not a single break has existed or can ever
take place. Just as the wave-form over a pebble in a stream
remains constant, though the particles of water which compose it
are ever changing, so the wave-form of life, which is heredity,
remains constant, though the bodies which exhibit it are continually
changing. The retrospection of heredity and memory, and the
prospection of thought, are well shown in Mrs. Meritt's beautiful
diagram."

This passage illustrates how parallel our thoughts were to
Mr. Butler's, whose work we did not then know. What we did
not see at the time was, that the power of thinking or memory
might antedate birth. It is quite impossible adequately to express
our sense of admiration of Mr. Butler's work.

Granting then the physical identity of offspring and parent, the
doctrine of heredity becomes plain. The child becomes like the
parent, because it is placed in almost identical circumstances to those
of its parent, and is indeed part of that parent. If memory be
possessed by all living matter, and this is what we now believe, we
can clearly see how heredity acts. The embryo develops into a man
like its parent, because human embryos have gone through this
process many times — till they are unconscious of the action, they
know how to proceed so thoroughly.

Darwin, after deeply pondering over the phenomena of growth,

r>

12 Colouration in Animals and Plants.

repair of waste and injury, heredity and kindred matters, advanced
what he wisely called a provisional hypothesis — pangenesis.

" I have been led," he remarks, " or, rather, forced, to form a view
which to a certain extent, connects these facts by a tangible method.
Everyone would wish to explain to himself even in an imperfect
manner, how it is possible for a character possessed by some
remote ancestor suddenly to reappear in the offspring ; how the
effects of increased or decreased use of a limb can be transmitted
to the child ; how the male sexual element can act, not solely on
the ovules, but occasionally on the mother form ; how a hybrid can
be produced by the union of the cellular tissue of two plants
independently of the organs of generation ; how a limb can be
reproduced on the exact line of amputation, with neither too much
nor too little added ; how the same organism may be produced by
such widely different processes as budding and true seminal gene-
ration ; and, lastly, how of two allied forms, one passes in the
course of its development through the most complex metamorphoses,
and the other does not do so, though when mature both are alike
in every detail of structure. I am aware that my view is merely
a provisional hypothesis or speculation ; but until a better one be
advanced, it will serve to bring together a multitude of facts which
are at present left disconnected by any efficient cause.*

After showing in detail that the body is made up of an infinite
number of units, each of which is a centre of more or less indepen-
dent action, he proceeds as follows : —

" It is universally admitted that the cells or units of the body
increase by self-division or proliferation, retaining the same nature,
and that they ultimately become converted into the various tissues
of the substances of the body. But besides this means of increase
I assume that the units throw off minute granules, which are
dispersed throughout the whole system ; that these, when supplied
with proper nutriment, multiply by self-division, and are ultimately
developed into units like those from which they were originally
derived. These granules may be called gemmules. They are
collected from all parts of the system to constitute the sexual
elements, and their development in the next generations forms a
new being; but they are likewise capable of transmission in a
dormant state to future generations, and may then be developed.
Their development depends on their union with other partially
• Animals and Plants under Domestication, vol. ii., p. 350.

Inherited Memory. 13

developed or nascent cells, which precede them in the regular course
of growth. . . . Gemmules are supposed to be thrown off by
every unit ; not only during the adult state, but during each stage
of development of every organ; but not necessarily during the
continued existence of the same unit. Lastly, I assume that the
gemmules in their dormant state have a mutual affinity for each
other, leading to their aggregation into buds, or into the sexual
elements. Hence, it is not the reproductive organs or buds which
generate new organisms, but the units of which each individual is
composed."*

Now, suppose that instead of these hypothetic gemmules we
endow the units with memory in ever so slight a degree, how
simple the explanation of all these facts becomes ! What an unit
has learned to do under given conditions it can do again under like
circumstances. Memory does pass from one unit to another, or we
could not remember anything as men that happened in childhood,
for we are not physically composed of the same materials. It is not
at all necessary that an unit should remember it remembers any
more than we in reading are conscious of the efforts we underwent
in learning our letters. Few of us can remember learning ta walk,
and none of us recollect learning to talk. Yet surely the fact that
we do read, and walk, and talk, proves that we have not forgotten
how.

Bearing in mind, then, the fundamental laws that the offspring
is one in continuity with its parents, and that memory arises chiefly
from repetition in a definite order (for we cannot readily reverse the
process — we cannot sing the National Anthem backwards), it is easy
to see how the oft-performed actions of an individual become its
unconscious habits, and these by inheritance become the instincts
and unconscious actions of the species. Experience and memory
are thus the key-note to the origin of species.

Granting that all living matter possesses memory, we must
admit that all actions are at first conscious in a certain degree, and
in the " sense of need " we have the great stimulation to action.

In Natural Selection, as expounded by Mr. Darwin, there is no
principle by which small variations can be accumulated. Take any
form, and let it vary in all directions. We may represent the
original form by a spot, and the variations by a ring of dots. Each
one of these dots may vary in all directions, and so other rings of

* Animals and Plants under Domestication, vol. ii., p. 370.

14 Colouration in Animals and Plants.

dots must be made, and so on, the result not being development
along a certain line, but an infinity of interlacing curves. The tree
of life is not like this. It branches ever outwards and onwards.
The eyes of the Argus pheasant and peacock have been formed by
the accumulation, through long generations, of more and more
perfect forms ; the mechanism of the eye and hand has arisen by
the gradual accumulation of more and more perfect forms, and these
processes have been continued along definite lines.

If we grant memory we eliminate this hap-hazard natural
selection. We see how a being that has once begun to perform a
certain action will soon perform it automatically, and when its habits
are confirmed its descendants will more readily work in this direction
than any other, and so specialisation may arise.

To take the cases of protective resemblance and mimicry.
Darwin and Wallace have to start with a form something like the
body mimicked, without giving any idea as to how that resemblance
could arise. But with this key of memory we can open nature's
treasure house much more fully. Look, for instance, at nocturnal
insects ; and one need not go further than the beetles (Blatta) in the
kitchen, to see that they have a sense of need, and use it. Suddenly
turn up the gas, and see the hurried scamper of the alarmed crowd.
They are perfectly aware that danger is at hand. Equally well do
they feel that safety lies in concealment ; and while all the foraging
party on the white floor are scuttling away into dark corners, the
fortunate dweller on the hearth stands motionless beneath the
shadow of the fire-irons ; a picture of keen, intense excitement, with
antenna) quivering with alertness. On the clean floor a careless
girl has dropped a piece of flat coal, and on it beetles stand
rigidly. They are as conscious as we are that the shadow, and the
colour of the coal afford concealment, and we cannot doubt that they
have become black from their sense of the protection they thus
enjoy. They do not say, as Tom, the Water Baby, says, " I must
be clean," but they know they must be black, and black they are.

There is, then, clearly an effort to assimilate in hue to their
surroundings, and the whole question is comparatively clear.

Mr. Wallace, in commenting upon the butterfly (Papilio nireus)—
which, at the Cape, in its chrysalis state, copies the bright hues of
the vegetation upon which it passes its dormant phase — says that
this is a kind of natural colour photography ; thus reducing the
action to a mere physical one. We might as well say the dun coat

Inherited Memory. 15

of tlio sportsman among the brown heather was acquired mechani-
cally. Moreover, Wallace distinctly shows that when the larvae are
made to pupate on unnatural colours, like sky-blue or vermilion,
the pupse do not mimic the colour. There is no reason why
" natural photography " should not copy this as well as the greens,
and browns, and yellows. But how easy the explanation becomes
when memory, the sense of need, and Butler's little "dose of
reason," are admitted ! For ages the butterfly has been acquainted
with greens, and browns, and yellows, they are every day experi-
ences ; but it has no acquaintance with aniline dyes, and therefore
cannot copy them.

The moral of all this is that things become easy by repetition;
that without experience nothing can be done well, and that the
course of development is always in one direction, because the
memory of the road traversed is not forgotten.

CHAPTER III.

INTRODUCTORY SKETCH.

NATURAL science has shown us how the existing colouration
of an animal or plant can be laid hold of and modified in
almost infinite ways under the influence of natural or artificial
evolution.

It shows us, for example, how the early pink leaf-buds have been
modified into attractive flowers to ensure fertilisation ; and it has
tracked this action through many of its details. It has explained
the rich hue of the bracts of Bougainvillea, in which the flowers
themselves are inconspicuous, and the coloured flower-stems in other
plants, as efforts to attract notice of the flower-frequenting insects.
It has explained how a blaze of colour is attained in some plants, as
in roses and lilies by large single flowers ; how the same effect is
produced by a number of small flowers brought to the same plane
by gradually increasing flower-stalks, as in the elderberry, or by
still smaller flowers clustered into a head, as in daisies and sun-
flowers.

It teaches us again how fruits have become highly coloured to
lure fruit-eating birds and mammals, and how many flowers are
striped as guides to the honey-bearing nectary.

Entering more into detail, we are enabled to see how the weird
walking-stick and leaf-insects have attained their remarkable pro-
tective resemblances, and how the East Indian leaf-butterflies are
enabled to deceive alike the birds that would fain devour them, and
the naturalist who would study them. Even the still more re-
markable cases of protective mimicry, in which one animal so
closely mimics another as to derive all the benefits that accrue to
its protector, are made clear.

Introductory Sketch. 17

All these and many other points have been deeply investigated,
and are now the common property of naturalists.

But up to the present no one has attempted systematically to
find out the principles or laws which govern the distribution of
colouration ; laws which underlie natural selection, and by which
alone it can work. Natural selection can show, for instance, how
the lion has become almost uniform in colour, while the leopard is
spotted, and the tiger striped. The lion living on the plains in open
country is thus rendered less conspicuous to his prey, the leopard
delighting in forest glades is hardly distinguishable among the
changing lights and shadows that flicker through the leaves, and
the tiger lurking amid the jungle simulates the banded shades of
the cane-brake in his striped mantle.

Beyond this, science has not yet gone ; and it is our
object to carry the study of natural colouration still further : to
show that the lion's simple coat, the leopard's spots, and the tiger's
stripes, are but modifications of a deeper principle.

Let us, as an easy and familiar example, study carefully the
colouration of a common tabby cat. First, we notice, it is darker
on the back than beneath, and this is an almost universal law. It
would, indeed, be quite universal among mammals but for some
curious exceptions among monkeys and a few other creatures of
arboreal habits, which delight in hanging from the branches in such
a way as to expose their ventral surface to the light. These
apparent exceptions thus lead us to the first general law, namely,
that colouration is invariably most intense upon that surface upon
which the light falls.

As in most cases the back of the animal is the most exposed,
that is the seat of mtensest colour. But whenever any modification
of position exists, as for instance in the side-swimming fishes like
the sole, the upper side is dark and the lower light.

The next point to notice in the cat is that from the neck, along
the back to the tail, is a dark stripe. This stripe is generally con-
tinued, but slighter in character across the top of the skull ; but it
will be seen clearly that at the neck the pattern changes, and the
skull-pattern is quite distinct from that on the body.

From . the central, or what we may call the back-bone stripe,
bands pass at a strong but varying angle, which we may call rib-
stripes.

Now examine the body carefully, and the pattern will be seen

18 Colouration in Animals and Plants.

to change at the shoulders and thighs, and also at each limb-joint.
In fact, if the cat be attentively remarked, it will clearly be seen
that the colouration or pattern is regional, and dependent upon the
structure of the cat.

Now a cat is a vertebrate or backboned animal, possessing four
limbs, and if we had to describe its parts roughly, we should specify
the head, trunk, limbs and tail. Each of these regions has its own
pattern or decoration. The head is marked by a central line, on
each side of which are other irregular lines, or more frequently
convoluted or twisted spots. The trunk has its central axial back-
bone stripe and its lateral rib-lines. The tail is ringed ; the limbs
have each particular stripes and patches. Moreover, the limb-
marks are largest at the shoulder and hip-girdles, and decrease
downwards, being smallest, or even wanting, on the feet ; and the
changes take place at the joints.

All this seems to have some general relation to the internal
structure of the animal. Such we believe to be the case ; and this
brings us to the second great law of colouration, namely, that it is
dependent upon the anatomy of the animal. We may enunciate
these two laws as folloAvs : —

I. THE LAW OF EXPOSURE. Colouration is primarily depen-

dent upon the direct action of light, being always most
intense upon that surface upon which the light falls most
directly.

II. THE LAW OF STRUCTURE. Colouration, especially where

diversified, follows the chief lines of structure, and
changes at points, such as the joints, where function
changes.

It is the enunciation and illustration of these two laws that
form the subject of the present treatise.

In the sequel we shall treat, in more or less detail, of each point
as it arises ; but in order to render the argument clearer, this chapter
is devoted to a general sketch of my views.

Of the first great law but little need be said here, as it is almost
self-evident, and has never been disputed. It is true not only of
the upper and under-sides of animals, but also of the covered and
uncovered parts or organs.

For example, birds possess four kinds of feathers, of which one
only, the contour feathers, occur upon the surface and are exposed

Introductory Sketch. 19

to the light. It is in these alone that we find the tints and patterns
that render birds so strikingly beautiful, the underlying feathers
being invariably of a sober grey. Still further, many of the contour
feathers overlap, and the parts so overlapped, being removed from
the light are grey also, although the exposed part may be resplen-
dent with the most vivid metallic hues. A similar illustration can
be found in most butterflies and moths. The upper wing slightly
overlaps the lower along the lower margin, and although the
entire surface of the upper wing is covered with coloured scales,
and the underwing apparently so as well, it will be found that the
thin unexposed margin is of an uniform grey, and quite devoid of
any pattern.

The law of structure, on the other hand, is an entirely new idea,
and demands more detailed explanation. Speaking in the broadest
sense, and confining ourselves to the animal kingdom, animals fall
naturally into two great sections, or sub-kingdoms, marked by the
possession or absence of an internal bony skeleton. Those which
possess this structure are known as Vertebrata, or backboned animals,
because the vertebral-column or backbone is always present. The
oilier section is called the Invertebrata, or backboneless animals.

Now, if we take the Vertebrata, we shall find that the system of
colouration, however modified, exhibits an unmistakably strong
tendency to assume a vertebral or axial character. Common
observation confirms this ; and the dark stripes down the backs of
horses, asses, cattle, goats, etc., are familiar illustrations. The only
great exception to this law is in the case of birds, but here, again,
the exception is more apparent than real, as will be abundantly
shown in the sequel. This axial stripe is seen equally well in
fishes and reptiles.

For our present purpose we may again divide the vertebrates
into limbed and limbless. Wherever we find limbless animals, such
as snakes, the dorsal stripe is prominent, and has a strong tendency
to break up into vertebra-like markings. In the limbed animals, on
the other hand, we find the limbs strongly marked by pattern, and
thus, in the higher forms the system of colouration becomes axial
and appendicular.

As a striking test of the universality of this law we may take
the cephalopoda, as illustrated in the cuttle-fishes. These creatures
are generally considered to stand at the head of the Mollusca, and
are placed, in systems of classification, nearest to the Vertebrata ;

E

20 Colouration in Animals and Plants.

indeed, they have even been considered to be the lowest type of
Vertebrates. This is owing to the possession of a hard axial organ,
occupying much the position of the backbone, and is the well-
known cuttle-bone. Now, these animals are peculiar amongst their
class, from possessing, very frequently, an axial stripe. We thus
see clearly that the dorsal stripe is directly related to the internal
axial skeleton.

Turning now to the invertebrata, we are at once struck with the
entire absence of the peculiar vertebrate plan of decoration ; and find
ourselves face to face with several distinct plans.

From a colouration point of view, we might readily divide the
animal kingdom into two classes, marked by the presence or absence
of distinct organs. The first of these includes all the animals except
the Protozoa — the lowest members of the animal kingdom — which
are simply masses of jelly-like protoplasm, without any distinct
organs.

Now, on our view, that colouration follows structure, we ought
to find an absence of decoration in this structureless group. This is
what we actually do find. The lowest Protozoa are entirely with-
out any system of colouring ; being merely of uniform tint, generally
of brown colour. As if to place this fact beyond doubt, we find in
the higher members a tendency to organization in a pulsating
vesicle, which constantly retains the same position, and may, hence,
be deemed an incipient organ. Now, this vesicle is invariably tinged
with a different hue from the rest of the being. We seem, indeed,
here to be brought into contact with the first trace of colouration,
and we find it to arise with the commencement of organization, and
to be actually applied to the incipient organ itself.

Ascending still higher in the scale, we come to distinctly organ-
ized animals, known as the Ccelenterata ; of which familiar examples
are found in the jelly-fishes and sea anemonies. These animals are
characterized by the possession of distinct organs, are transparent,
or translucent, and the organs are arranged radially.

No one can have failed to notice on our coasts, as the filmy jelly-
fishes float by, that the looped canals of the disc are delicately
tinted with violet ; and closer examination will show the radiating
muscular bands as pellucid white lines ; and the sense organs fring-
ing the umbrella are vividly black— the first trace of opaque colour-
ation in the animal kingdom.

These animals were of yore united with the star-fishes and sea-

Introductory Sketch. 21

urchins, to form the sub-kingdom Radiata, because of their radiate
structure. Now, in all these creatures we find the system of colour-
ation to be radiate also.

Passing to the old sub-kingdom Articulata, which includes the
worms, crabs, lobsters, insects, etc., we come to animals whose
structure is segmental ; that is to say, the body is made up of a
number of distinct segments. Among these we find the law holds,
rigidly that the colouration is segmental also, as may be beautifully
seen in lobsters and caterpillars.

Lastly, we have the Molluscs, which fall for our purpose into two
classes, the naked and the shelled. The naked molluscs are often
most exquisitely coloured, and the feathery gills that adorn many
are suffused with some of the most brilliant colours in nature.
The shelled molluscs differ from all other animals, in that the
shell is a secretion, almost as distinct from the animals as a house is
from its occupant. This shell is built up bit by bit along its margin
by means of a peculiar organ known as the mantle —its structure
is marginate — its decoration is marginate also.

We have thus rapidly traversed the animal kingdom, and find
that in all cases the system of decoration follows the structural
peculiarity of the being decorated. Thus in the : —

Structureless protozoa there is no varying colouration.
Radiate animals — the system is radiate.
Segmented „ ,, segmental.

Marginate „ „ marginal.

Vertebrate „ „ axial.

We must now expound this great structural law in detail, and we
shall find that all the particular ornamentations in their various
modifications can be shown to arise from certain principles,
namely —

1. The principle of Emphasis,

2. The „ Repetition.

The term Emphasis has been selected to express the marking out
or distinguishing of important functional or structural regions by
ornament, either as form or colour. It is with colour alone that we
have to deal.

Architects are familiar with the term emphasis, as applied to
the ornamentation of buildings. This ornamentation, they say,
should emphasize, point out, or make clear to the eye, the use or

22 Colouration in Animals and Plants.

function of the part emphasized. They recognise the fact that to
give sublimity and grace to a building, the ornamentation must be
related to the character of the building as a whole, and to its parts
in particular.

Thus in a tower whose object or function is to suggest height,
the principal lines of decoration must be perpendicular, while in the
body of a building such as a church, the chief lines must be
horizontal, to express the opposite sentiment. So, too, with indi-
vidual parts. A banded column, such as we see in Early English
Gothic, looks weak and incapable of supporting the superincumbent
weight. It suggests the idea that the shaft is bound up to
strengthen it. On the other hand, the vertical flutings of a Greek
column, at once impress us with their function of bearing vertical
pressure and their power to sustain it.

This principle is carried into colour in most of our useful arts.
The wheelwright instinctively lines out the rim and spokes and does
not cross them, feeling that the effect would be to suggest weak-
ness. Moreover, in all our handicraft work, the points and tips are
emphasized with colour.

This principle seems to hold good throughout nature. It is not
suggested that the colouration is applied to important parts in
order to emphasize them, but rather that being important parts, they
have become naturally the seats of most vivid colour. How this
comes about we cannot here discuss, but shall refer to it further on.

It is owing to this pervading natural principle, that we find the
extreme points of quadrupeds so universally decorated. The tips
of the nose, ears and tail, and the feet also proclaim the fact, and
the decoration of the sense organs, even down to the dark spots
around each hair of a cat's feelers, are additional proofs. Look, for
instance, at a caterpillar with its breathing holes or spiracles along
the sides, and see how these points are selected as the seats of
specialized colour, eye-spots and stripes in every variety will be
seen, all centred around these important air-holes.

This leads us to our second principle, that of repetition, which
simply illustrates the tendency to repeat similar markings in like
areas. Thus the spiracular marks are of the same character on
each segment.

The principle of repetition, however, goes further than this, and
tends to repeat the style of decoration upon allied parts. We see
this strongly in many caterpillars in which spiracular markings are

Introductory Sketch. 23

continued over the segments which lack spiracles; and it is probably
owing to this tendency that the rib-like markings on so many
mammals are continued beyond the ribs into the dorsal region.

Upon these two principles the whole of the colouration of nature
seems to depend. But the plan is infinitely modified by natural
selection, otherwise the result would have been so patent as to need
no elucidation.

Natural selection acts by suppressing, or developing, structurally
distributed colour. So far as our researches have gone, it seems
most probable that the fundamental or primitive colouration is
arranged in spots. These spots may expand into regular or
irregular patches, or run into stripes, of which many cases will be
given in the sequel. Now, natural selection may suppress certain
spots, or lines, or expand them into wide, uniform masses, or it may
suppress some and repeat others. On these simple principles the
whole scheme of natural colouration can be explained ; and to do
this is the object of the following pages.

Into the origin of the colour sense it is not our province to
enlarge ; but, it will reasonably be asked, How are these colours of
use to the creature decorated ? The admiration of colour, the charm
of landscape, is the newest of human developments. Are we, then,
to attribute to the lower animals a discriminative power greater
than most races of men possess, and, if so, on the theory of evolu-
tion, how comes it that man lost those very powers his remote
ancestors possessed in so great perfection ? To these questions we
will venture to reply.

Firstly, then, it must be admitted that the higher animals do
actually possess this power ; and no one will ever doubt it if he
watches a common hedge-sparrow hunting for caterpillars. To see
this bird carefully seeking the green species in a garden, and
deliberately avoiding the multitudes of highly coloured but nauseous
larvae on the currant bushes, arduously examining every leaf and
twig for the protected brown and green larvae which the keen eye
of the naturalist detects only by close observation ; hardly deigning
to look at the speckled beauties that are feeding in decorated safety
before his eyes, while his callow brood are clamouring for food — to
see this is to be assured for ever that birds can, and do, discriminate
colour perfectly. What is true of birds can be shown to be true of
other and lower types ; and this leads us to a very important
conclusion— that colouration has been developed with the evolution

24 Colouration in Animals and Plants.

of the sense of sight. We can look back in fancy to the far off ages,
when no eye gazed upon the world, and we can imagine that then
colour in ornamental devices must have been absent, and a dreary
monotony of simple hues must have prevailed.

With the evolution of sight it might be of importance that even
the sightless animals should be coloured ; and in this way we can
account for the decoration of coral polyps, and other animals that
have no eyes; just as we find no difficulty in understanding the
colouration of flowers.

Colour, in fact, so far as external nature is concerned, is all iu
all to the lower animals. By its means prey is discovered, or foes
escaped. But in the case of man quite a different state of things
exists. The lower animals can only be modified and adapted to
their surroundings by the direct influence of nature. Man, on the
other hand, can utilise the forces of nature to his ends. He does not
need to steal close to his prey — he possesses missiles. His arm, in
reality, is bounded, not by his finger tips, but by the distance to
which he can send his bolts. He is not so directly dependent upon
nature ; and, as his mental powers increase, his dependence lessens,
and in this way — the aesthetic principle not yet being awakened —
we can understand how his colour sense, for want of practice,
decayed, to be reawakened in these our times, with a vividness and
power as unequalled as is his mastery over nature — the master of
his ancestors.

CHAPTER IV.

COLOUR, ITS NATURE AND RECOGNITION.

THIS chapter will be devoted to a slight sketch of the nature
of light and colour, and to proofs that niceties of colour are
distinguished by animals.

First, as to the nature of light and colour. Colour is essentially
the effect of different kinds of vibrations upon certain nerves.
Without such nerves, light can produce no luminous effect what-
ever ; and to a world of blind creatures, there would be neither
light nor colour, for as we have said, light and colour are not
material things, but are the peculiar results or effects of vibrations
of different size and velocity.

These effects are due to the impact of minute undulations or
waves, which stream from luminous objects, the chief of which is
the sun. These waves are of extreme sraallness, the longest being
only 226 ten-millionths of an inch from crest to crest. The tiny
billows roll outwards and onwards from their scource at incon-
ceivable velocities, their mean speed being 185,000 miles in a
second. Could we see these light billows themselves and count
them as they rolled by, 450 billions (450,000,000,000,000) would
pass in a single second, and as the last ranged alongside us, the
first would be 185,000 miles away. We are not able, however, to
see the waves themselves, for the ocean whose vibrations they are.
is composed of matter infinitely more transparent than air, and
infinitely less dense. Light, then, be it clearly understood, is not
the ethereal billows or waves themselves, but only the effect they
produce on falling upon a peculiar kind of matter called the optic
nerve. When the same vibrations fall upon a photographic sensi-
tive film, another effect — chemical action — is produced : when they

26 Colouration in Animals and Plants.

fall upon other matter, heat is the result. Thus heat, light and
chemical action are but phases, expressions, effects or results of
the different influences of waves upon different kinds of matter.
The same waves or billows will affect the eye itself as light, the
ordinary nerves as warmth, arid the skin as chemical action, in
tanning it.

Though we cannot see these waves with the material eye, they
are visible indeed to the mental eye ; and are as amenable to
experimental research as the mightiest waves of the sea. Still, to
render this subject clearer, we will use the analogy of sound. A
musical note, we all know, is the effect upon our ears of regularly
recurring vibrations. A pianoforte wire emits a given note, or in
other words, vibrates at a certain and constant rate. These vibra-
tions are taken up by the air, and by it communicated to the ear,
and the sensation of sound is produced. Here we see the wire
impressing its motion on the air, and the air communicating its
motion to the ear; but if another wire similar in all respects is
near, it will also be set in motion, and emit its note ; and so will
any other body that can vibrate in unison. Further, the note of
the pianoforte string is not a simple tone, but superposed, as it
were, upon the fundamental note, are a series of higher tones,
called harmonics, which give richness. Now, a ray of sun-light
may be likened to such a note ; it consists not of waves all of a
certain length or velocity, but of numbers of waves of different
lengths and speed. When all these fall upon the eye, the sensation
of white light is produced, white light being the compound effect,
like the richness of the tone of the wire and its harmonies ; or we
may look upon it as a luminous chord. When light strikes on any
body, part or all is reflected to the eye. If all the waves are thus
reflected equally, the result is whiteness. If only a part is reflected, the
effect is colour, the tint depending upon the particular waves
reflected. If none of the waves are reflected, the result is
blackness.

Colour, then, depends upon the nature of the body reflecting
light. The exact nature of the action of the body upon the light
is not known, but depends most probably upon the molecular con-
dition of the surface. Bodies which allow the light to pass through
them, are in like manner coloured according to the waves they
allow to pass.

We find in nature, however, a somewhat different class of

Colour, its Nature and Recognition. 27

colour, namely, the iridescent tints, like mother of pearl or shot
silk, which give splendour to such butterflies, as some Morphos and
the Purple Emperor. These are called diffraction colours, and are
caused by minute lines upon the reflecting surface, or by thin
transparent films. These lines or films must be so minute that the
tiny light waves are broken up among them, and are hence reflected
irregularly to the eye.

Dr. Hagen has divided the colours of insects into two classes,
the epidermal and hypodermal. The epidermal colours are pro-
duced in the external layer or epidermis which is comparatively
dry, and are persistent, and do not alter after death. Of this nature
are the metallic tints of blue, green, bronze, gold and silver, and
the dead blacks and browns, and some of the reds. The hypo-
dermal colours are formed in the moister cells underlying the
epidermis, and on the drying up of the specimen fade, as might
be expected. They show through the epidermis, which is more or
less transparent. These colours are often brighter and lighter in
hue than the epidermal ; and such are most of the blues, and greens,
and yellow, milk white, orange, and the numerous intermediate
shades. These colours are sometimes changeable by voluntary act,
and the varying tints of the chameleon and many fishes are of this
character.

In this connection, Dr. Hagen remarks, that probably all mimetic
colours are hypodermal. The importance of this suggestion will
be seen at once, for it necessitates a certain consciousness or
knowledge on the part of the mimicker, which we have shown, seems
to be an essential factor in the theory of colouration.

This author further says, that " the pattern is not the product
of an accidental circumstance, but apparently the product of a
certain law, or rather the consequence of certain actions or wants
in the interior of the animal and in its development."

This remarkable paper, to which our attention was called after
our work was nearly completed, is the only record we have been able
to find which recognises a law of colouration.

From what has been said of the nature of light, and the physical
origin of colour, we see that to produce any distinct tint such as
red, yellow, green, or blue, a definite physical structure must be
formed, capable of reflecting certain rays of the same nature and
absorbing others. Hence, whenever we see any distinct colour, we
may be sure that a very considerable development in a certain

F

28 Colouration in Animals and Plants.

direction has taken place. This is a most important conclusion,
though not very obvious at first sight. Still, when we bear in
mind the numbers of light waves of different lengths, and know
that if these are reflected irregularly, we get only mixed tints such
as indefinite browns ; we can at once see how, in the case of such
objects as tree trunks, and, still more, in inanimate things like rocks
and soils, these, so-to-say, undifferentiated hues are just what we
might expect to prevail, and that when definite colours are pro-
duced, it of necessity implies an effort of some sort. Now, if this
be true of such tints as red and blue, how much more must it be
the case with black and white, in which all the rays are absorbed
or all reflected? These imply an even stronger effort, and a priori
reasoning would suggest that where they occur, they have been
developed for important purposes by what may be termed a
supreme effort. Consequently, we find them far less common than
the others ; and it is a most singular fact that in mimetic insects,
these are the colours that are most frequently made use of. It
would almost seem as if a double struggle had gone on: first, the
efforts which resulted in the protective colouring of the mimicked
species, and then a more severe, because necessarily more rapid,
struggle on the part of the mimicker.

Yet another point in this connection. If this idea be correct,
it follows that a uniformly coloured flower or animal must be of
extreme rarity, since it necessitates not merely the entire suppres-
sion of the tendency to emphasize important regions in colour, but
also the adjustment of all the varying parts of the organism to
one uniform molecular condition, which enables it to absorb all
but a certain closely related series of light waves no matter how
varied the functions of the parts. Now, such "self-coloured"
species, as florists would call them, are not only rare, but,
as all horticulturists know, are extremely difficult to produce.
When a pansy grower, for instance, sets to work to produce a self-
coloured flower— say a white pansy without a dark eye— his
difficulties seem insurmountable. And, in truth, this result has
never been quite obtained ; for he has to fight against every natural
tendency of the plant to mark out its corolla-tube in colour, and
when this is overcome, to still restrain it, so as to keep it within
those limits which alone allow it to reflect the proper waves of light.

The production of black and white, then, being the acme of colour
production, we should expect to find these tints largely used for

To face page 28.]

rjji.-. VD
Plate I.

KALLIMA 1NACHUS.

Colour, its Nature and Recognition. 29

very special purposes. Such is actually the case. The sense organs
are frequently picked out with black, as witness the noses of dogs,
the tips of their ears, the insertion of their vibrissae, or whiskers, and
so on ; and white is the most usual warning or distinctive colour, as
we see in the white stripes of the badger and skunk, the white spots
of deer, and the white tail of the rabbit.

Colour, then, as expressed in definite tints and patterns, is no
accident; for although, as Wallace has well said, "colour is the
normal character," yet we think that this colour would, if unrestrained
and undirected, be indefinite, and could not produce definite tints,
nor the more complicated phenomenon of patterns, in which definite
hues are not merely confined to definite tracts, but so frequently
contrasted in the most exquisite manner. As we write, the beautiful
Red Admiral (Pi atalantd) is sporting in the garden; and who can
view its glossy black velvet coat, barred with vividest crimson, and
picked out with purest snow white, and doubt for an instant that its
robe is not merely the product of law, but the supreme effort of an
important law? Mark the habits of this lovely insect. See how
proudly it displays its rich decorations ; sitting with expanded
wings on the branch of a tree, gently vibrating them as it basks in
the bright sunshine ; and you know, once and for all, that the object
of that colour is display. But softly — we have moved too rudely,
and it is alarmed. The wings close, and where is its beauty now ?
Hidden by the sombre specklings of its under wings. See, it has
pitched upon a slender twig, and notice how instinctively (shall we
say ?) it arranges itself in the line of the branch : if it sat athwart it
would be prominent, but as it sits there motionless it is not only
almost invisible, but it knows it ; for you can pick it up in your hands,
as we have done scores of times. It is not enough, if we would know
nature, to study it in cabinets. There is too much of this dry-bone
work in existence. The object of nature is life; and only in living
beings can we learn how and why they fulfil their ends.

Here, in this common British butterfly, we have the whole
problem set before us— vivid colour, the result of intense and long
continued effort ; grand display, the object of that colour ;
dusky, indefinite colour, for concealment; and the "instinctive"
pose, to make that protective colour profitable. The insect knows
all this in some way. How it knows we must now endeavour to
find out.

In attacking this problem we must ask ourselves, What are the

30 Colouration in Animals and Plants.

purposes that colouration, and, especially, decoration, can alone
subserve ? We can only conceive it of use in three ways : first, as
protection from its enemies ; second, as concealment from its prey ;
third, as distinctive for its fellows. To the third class may be
added a sub-class — attractiveness to the opposite sex.

The first necessity would seem to be distinctness of species ; for,
unless each species were separately marked, it would be difficult for
the sexes to discriminate mates of their own kind, in many
instances; and this is, doubtless, the reason why species are differ-
ently coloured.

But protective resemblance, as in Kallima* the Leaf-butterfly, and
mimicry, as in D. niavius and P. meropej sometimes so hide the
specific characters that this process seems antagonistic to the prime
reason for colouration, by rendering species less distinct. Now,
doubtless, protective colouring could not have been so wonderfully
developed if the organ of sight were the only means of recognition. But
it is not. Animals possess other organs of recognition, of which, as
everyone knows, smell is one of the most potent. A dog may have
forgotten a face after years of absence, but, once his cold nose has
touched your hand, the pleased whine and tail-wagging of recogni-
tion, tells of awakened memories. Even with ourselves, dulled as
our senses are, the odour of the first spring violet calls up the past;
as words and scenes can never do. What country-bred child forgets
the strange smell of the city he first visits ? and how vividly the
scene is recalled in after years by a repetition of that odour I

But insects, and, it may be, many other creatures, possess sense
organs whose nature we know not. The functions of the antenna?
and of various organs in the wings, are unknown ; and none can
explain the charm by which the female Kentish Glory, or Oak
Egger moths lure their mates. You may collect assiduously, using
every seduction in sugars and lanterns, only to find how rare are
these insects; but if fortune grant you a virgin female, and you
cage her up, though no eye can pierce her prison walls, and though
she be silent as the oracles, she will, in some mysterious way, attract
lovers ; not singly, but by the dozen ; not one now and another in
an hour, but in eager flocks. Many butterflies possess peculiar
scent-pouches on their wings, and one of these, a Danais, is
mimicked by several species. It is the possession of these additional
powers of recognition that leaves colouration free to run to the
* PI. I., Figs 1-3. t PI. II., Figs. 1-3.

To face page. 30.)

Plate II.

MIMICRY,

Colour, its Nature and Recognition. 31

extreme of protective vagary, when the species is hard pressed in
the struggle for life.

Nevertheless, though animals have other means of recognition,
the distinctive markings are, without doubt, the prime means of
knowledge. Who, that has seen a peacock spread his glorious
plumes like a radiant glory, can doubt its fascination? Who, that
has wandered in America, and watched a male humming-bird
pirouetting and descending in graceful spirals, its whole body
throbbing with ecstasy of love and jealousy, can doubt? Who can
even read of the Australian bower-bird, lowliest and first of virtuosi,
decorating his love-bower with shells and flowers, and shining
stones, running in and out with evident delight, and re-arranging his
treasures, as a collector does his gems, and not be certain that here,
at least, we have the keenest appreciation, not only of colour, but of
beauty — a far higher sense *?

It has been said that butterflies must be nearly blind, because
they seldom fly directly over a wall, but feel their way up with airy
touches. Yet every fact of nature contradicts the supposition.
Why have plants their tinted flowers, but to entice the insects
there ? Why are night-blooming flowers white, or pale yellows and
pinks, but to render them conspicuous ? Why are so many flowers
striped in the direction of the nectary, but to point the painted way
to the honey-treasures below ? The whole scheme of evolution, the
whole of the new revelation of the meanings of nature, becomes a dead
letter if insects cannot, appreciate the hues of flowers. The bee
confines himself as much as possible to one species of flower at a
time, and this, too, shows that it must be able to distinguish them
with ease. We may, then, take it as proven that the power of
discriminating colours is possessed by the lower animals.

CHAPTER V.

THE COLOUR SENSE.

THE previous considerations lead us, naturally, to enquire in what
manner the sense of colour is perceived.

In thinking over this obscure subject, the opinion has steadily
gathered strength that form and colour are closely allied ; for form
is essential to pattern; and colour without pattern, that is to say,
colour indefinitely marked, or distributed, is hardly decoration at all,
in the sense we are using the term. That many animals possess
the power of discriminating form is certain. Deformed or monstrous
forms are driven from the herds and packs of such social animals
as cattle, deer, and hogs, and maimed individuals are destroyed.
Similar facts have been noticed in the case of birds. This shows a
power of recognising any departure from the standard of form, just
as the remorseless destruction of abnormally coloured birds, such as
white or piebald rooks and blackbirds, by their fellows, is proof of
the recognition and dislike of a departure from normal colouring.
Authentic anecdotes of dogs recognising their masters' portraits are
on record; and in West Suffolk, of late years, a zinc, homely
representation of a cat has been found useful in protecting garden
produce from the ravages of birds. In this latter case the birds
Boon found out the innocent nature of the fraud, for we have noticed,
after a fortnight, the amusing sight of sparrows cleaning their beaks
on the whilom object of terror. Many fish are deceived with
artificial bait, as the pike, with silvered minnows; the salmon, and
trout, with artificial flies ; the glitter of the spoon-bait is often most
attractive; and mackerel take greedily to bits of red flannel. Bees
sometimes mistake artificial for real flowers; and both they and
butterflies have been known to seek vainly for nourishment from

The Colour Sense. 33

the gaudy painted flowers on cottage wall-papers. Sir John
Lubbock has demonstrated the existence of a colour sense in bees,
wasps, and ants; and the great fact that flowers are lures for insects
proves beyond the power of doubt that these creatures have a very
strong faculty for perceiving colour.

The pale yellows and white of night-flowering plants render
them conspicuous to the flower-haunting moths; and no one who
has ever used an entomologist's lantern, or watched a daddy-long-
legs (Tipuld) dancing madly round a candle, can fail to see that
intense excitement is caused by the flame. In the dim shades of
night the faint light of the flowers tells the insects of the land of
plenty, and the stimulus thus excited is multiplied into a frenzy by
the glow of a lamp, which, doubtless, seems to insect eyes the
promise of a feast that shall transcend that of ordinary flowers, as
a Lord Mayor's feast transcends a homely crust of bread and
cheese.

We take it, then, as proven that the colour sense does exist, ah
least, in all creatures possessing eyes. But there are myriads of
animals revelling in bright tints ; such as the jelly-fishes and
anemones, and even lower organisms, in which eyes are either
entirely wanting or are mere eye-specks, as will be explained in the
sequel. How these behave with regard to colour is a question
that may, with propriety, be asked of science, but to which, at
present, we can give no very definite reply. Still, certain modern
researches open to us a prospect of being able, eventually, to decide
even this obscure problem.

The question, however, is not a simple one, but involves two
distinct principles; firstly, as to how colour affects the animal
coloured, and, secondly, how it affects other animals. In other
words, How does colour affect the sensibility of its possessor ? and
how does it affect the sense organs of others ?

To endeavour to answer the first question we must start with
the lowest forms of life, and their receptivity to the action of light ;
for, as colour is only a differentiation of ordinary so-called white
light, we might a priori expect that animals would show sensibility
to light as distinguished from darkness, before they had the power
of discriminating between different kinds of light.

This appears to be the case, for Engelmann has shown* that many

* Pfliiger's Archiv. f. d. ges. Phys. Bd. xxix, 1882, quoted by Eomanes. Mental
Evolution, p. 80, 1883. Op. cit. p. 80.

34 Colouration in Animals and Plants.

of the lowest forms of life, which are almost mere specks of proto-
plasm, are influenced by light, some seeking and others shunning it.
He found, too, that in the case of Euglena viridis it would seek the
light only if it " were allowed to fall upon the anterior part of the
body. Here there is a pigment spot ; but careful experiment showed
that this was not the point most sensitive to light, a colourless and
transparent area of protoplasm lying in front of it being found to be
so." Commenting upon this Romanes observes, " it is doubtful
whether this pigment spot is or is not to be regarded as an exceed-
ingly primitive organ of special sense." Haeckel has also made
observations upon those lowest forms of life, which, being simply
protoplasm without the slightest trace of organization, not even
possessing a nucleus, form his division Protista, occupying the no-
man's-land between the animal and vegetable kingdoms. He finds
that " already among the microscopic Protista there are some that
love light, and some that love darkness rather than light. Many
seem also to have smell and taste, for they select their food with
great care. . . . Here, also, we are met by the weighty fact that
sense-function is possible without sense organs, without nerves. In
place of these, sensitiveness is resident in that wondrous, structure-
less, albuminous substance, which, under the name of protoplasm, or
organic formative material, is known as the general and essential
basis of all the phenomena of life."*

Now, whether Romanes be correct in doubting whether the
pigment-spot in Euglena is a sense organ or not, matters little to
our present enquiry, but it certainly does seem that the spot, ivith
its accompanying clear space, looks like such an organ. And when
we are further told that after careful experiment it is found that
Euglena viridis prefers blue to all the colours of the spectrum, the
fundamental fact seems to be established that even as low down as
this the different parts of the spectrum affect differently the body of
creatures very nearly at the bottom of the animal scale. This
implies a certain selection of colour, and, equally, an abstention from
other colours.

It is not part of our scheme, however, to follow out in detail the
development of the organs of special sense, and the reader must be
referred to the various works of Mr. Romanes, who has worked long
and successfully at this and kindred problems. Suffice it to say that
in this and other cases he has been led to adopt the theory of
* Quoted by Romanes, op. cit. p. 81.

The Colour Sense. 35

inherited memory, though not, as we believe, in the fulness with
which it must ultimately be acquired.

This, however, seems certain, that the development, not only of
the sense organs, but of organs in general — that is, the setting aside
of certain portions for the performance of special duties, and the
modifications of those parts in relation to their special duties, is
closely related to the activity of the organism. Thus, we find in
those animals, like some of the Ccelenterata, which pass some
portion of their existence as free-swimming beings, and the remainder
in a stationary or sessile condition, that the former state is the most
highly organized. This is shown to a very remarkable degree in the
Sea Squirts (Ascidians), a class of animals that are generally
grouped with the lower Mollusca, but which Prof. Ray Lankester
puts at the base of the Vertebrata.

These animals are either solitary or social, fixed or free; but
even when free, have little or no power of locomotion, simply float-
ing in the sea. Their embryos are, however, free-swimming, and
some of the most interesting beings in nature. Some are marvell-
ously like young tadpoles, and possess some of the distinctive
peculiarities of the Vertebrata. Thus, the body is divided into a
head and body, or tail, as in tadpoles. The head contains a large
nerve centre, corresponding with the brain, which is produced back-
wards into a chord, corresponding to the spinal chord. In the
head, sense organs are clearly distinguishable; there is a well-
marked eye, an equally clear ear, and a less clearly marked olfac-
tory organ. Besides this, the spinal-cord is supported below by
a rod -like structure, called the notochord. In the vertebrate
embryo this structure always precedes the development of the
true vertebral column, and in the lowest forms is persistent through
life.

We have thus, in the ascidian larva, a form which, if permanent,
would most certainly entitle it to a place in the vertebrate sub-
kingdom. It is now an active free-swimming creature, but as
maturity approaches it becomes fixed, or floating, and all this pre-
figurement of a high destiny is annulled. The tail, with its nervous
cord and notochord atrophies, and in the fixed forms, not only do
the sense organs pass away, but the entire nervous system is
reduced to a single ganglion, and the creature becomes little more
than an animated stomach. It is, as Ray Lankester has pointed out,
a case of degeneration. In the floating forms, which still possess a

36 Colouration in Animals and Plants.

certain power of locomotion, this process is not carried to such
extremes, and the eye is left.

Now, cases of this kind are important as illustrating the direct
connection between an active life and advancement ; and they also
add indirectly to the view Wallace takes of colouration, namely,
that the most brilliant colour is generally applied to the most highly
modified parts, and is brightest in the seasons of greatest activity.

But they have a higher meaning also, for they may point us to
the prime cause of the divergence of the animal and vegetable
kingdoms. In thinking over this matter, one of us ventured to
suggest that probably the reason why animals dominate the world,
and not plants, is, that plants are, as a rule, stationary, and animals
lead an active existence. We can look back to the period prior to
the divergence of living protoplasm into the two kingdoms. Two
courses only were open to it, either to stay at home, and take what
came in its way, or to travel, and seek what was required. The
stay-at-homes became plants, and the gad-abouts animals. In a
letter it was thus put ; " It is a truly strange fact that a free-swim-
ming, sense-organ-bearing animal should degenerate into a fixed
feeding and breeding machine. It seems to me that the power of
locomotion is a sine qua non for active development of type, as it
necessarily sharpens the wits by bringing fresh experiences and
unlooked-for adventures to the creature. I almost think, and this,
I believe may be a great fundamental fact, that the only reason
why animals rule the world instead of plants is that plants elected
to stay at home, and animals did not. They had equal chances.
Both start as active elements ; the one camps down, and the other
looks about him."

Talking over this question with Mr. Butler, he astonished the
writer by quoting from his work, "Alps and Sanctuaries" (p. 196),
the following passage : —

" The question of whether it is better to abide quiet, and take
advantage of opportunities that come, or to go farther afield in
search of them, is one of the oldest which living beings have to deal
with. It was on this that the first great schism or heresy arose in
what was heretofore the catholic faith of protoplasm. The schism
still lasts, and has resulted in two great sects — animals and plants.
The opinion that it is better to go in search of prey is formulated in
animals ; the other — that it is better, on the whole, to stay at home,

The Colour Sense. 37

and profit by what comes — in plants. Some intermediate forms still
record to us the long struggle during which the schism was not yet
complete.

" If I may be pardoned for pursuing this digression further, T
would say that it is the plants, and not we, who are the heretics.
There can be no question about this ; we are perfectly justified,
therefore, in devouring them. Ours is the original and orthodox
belief, for protoplasm is much more animal than vegetable. It is
much more true to say that plants have descended from animals
than animals from plants. Nevertheless, like many other heretics,
plants have thriven very fairly well. There are a great many of
them, and, as regards beauty, if not wit — of a limited kind, indeed,
but still wit — it is hard to say that the animal kingdom has the
advantage. The views of plants are sadly narrow; all dissenters
are narrow-minded ; but within their own bounds they know the
details of their business sufficiently well — as well as though they
kept the most nicely-balanced system of accounts to show them
their position. They are eaten, it is true ; to eat them is our
intolerant and bigoted way of trying to convert them: eating is
only a violent mode of proselytizing, or converting ; and we do
convert them — to good animal substance of our own way of
thinking. If we have had no trouble we say they have ' agreed '
with us ; if we have been unable to make them see things from
our point of view, we say they ' disagree ' with us, and avoid being
on more than distant terms with them for the future. If we have
helped ourselves to too much, we say we have got more than we
can ' manage.' And an animal is no sooner dead than a plant will
convert it back again. It is obvious, however, that no schism could
have been so long successful without having a good deal to say for
itself. t

" Neither ^>arty has been quite consistent. Whoever is or can
be ? Every extreme — every opinion carried to its logical end will
prove to be an absurdity. Plants throw out roots and boughs and
leaves : this is a kind of locomotion ; and as Dr. Erasmus Darwin
long since pointed out, they do sometimes approach nearly to what
is called travelling ; a man of consistent character will never look at
a bough, a root, or a tendril, without regarding it as a melancholy
and unprincipled compromise. On the other hand, many animals are
sessile ; and some singularly successful genera, as spiders, are in the
main liers-in-wait."

38

Colouration in Animals and Plants.

This exquisitively written passage the writer was quite unaware
of having read, though he possessed and had perused the work
quoted, nor can he understand how such an admirable exposition
could have escaped notice. Had he read it : had he assimilated it
so thoroughly as to be unconscious of its existence ; is this a case of
rapid growth of automatism ? He cannot say.

To return to the main point, it would seem that specialization is
directly proportionate to activity, and when we compare the infinitely
diverse organization of the animal with the comparative simplicity
of the vegetable world, this conclusion seems to be inevitable.

CHAPTER VI.

SPOTS AND STRIPES.

BEARING in mind the great tendency to repetition and symmetry
of marking we have shown to exist, it becomes an interesting
question to work out the origin of the peculiar spots, stripes, loops
and patches which are so prevalent in nature. The exquisite eye-
spots of the argus pheasant, the peacock, and many butterflies and
moths have long excited admiration and scientific curiosity, and have
been the subject of investigation by Darwin,* the Rev. H. H.
Higgins, t Weismann, } and others, Darwin having paid especial
attention to the subject.

His careful analysis of the ocelli or eye-spots in the Argus pheasant
and peacock have led him to conclude that they are peculiar modifi-
cations of the bars of colour as shown by his drawings. Our own
opinion, founded upon a long series of observations, is that this is
not the whole case, but that, in the first place, bars are the result
of the coalescence of spots. It is not pretended that a bar of colour
is the result of the running together of a series of perfect ocelli like
those in the so-called tail of the peacock, but merely that spots of
colour are the normal primitive commencement of colouring, and
that these spots may be developed on the one hand into ocelli or eye-
spots, and on the other into bars or even into great blotches of a
uniform tint, covering large surfaces.

Let us first take the cases of abnormal marking as shown in
disease. An ordinary rash, as in measles, begins as a set of minute
red spots, and the same is the case with small pox, the pustules of
which sometimes run together, and becoming confluent form bars,

* Descent of Man, vol. ii., p. 132. f Quart. Journ. Sci., July 1868, p. 325.

t Studies in the Theory of Descent.

40 Colouration in Animals and Plants.

which again enlarging meet and produce a blotch or area abnormally
marked. It was these well-known facts that induced us to re-
examine this question. Colouration and discolouration arise from the
presence or absence of pigment in cells, and thus having, as it were
independent sources, we should expect colour first to appear in spots.
We have already stated, and shall more fully show in the sequel, how
colouration follows structure, and would here merely remark that it
seems as if any peculiarity of structure, or intensified function
modifying structure, has a direct tendency to influence colour. Thus
in the disease known as frontal herpes, as pointed out to us by Mr.
Bland Sutton, of the Middlesex Hospital, the affection is charac-
terized by an eruption on the skin corresponding exactly to the
distribution of the ophthalmic division of the fifth cranial nerve,
mapping out all its little branches, even to the one which goes to the
tip of the nose. Mr. Hutchinson, F.R.S., the President of the
Pathological Society, who first described this disease, has favoured
us with another striking illustration of the regional distribution of
the colour effects of herpes. In this case decolouration has taken
place. The patient was a Hindoo, and upon his brown skin the
pigment has been destroyed in the arm along the course of the
ulnar nerve, with its branches along both sides of one finger and the
half of another. In the leg the sciatic and saphenous nerves are
partly mapped out, giving to the patient the appearance of an
anatomical diagram.*

In these cases we have three very important facts determined.
First the broad fact that decolouration and colouration in some cases
certainly follow structure ; second, that the effect begins as spots ;
thirdly, that the spots eventually coalesce into bands and blotches.

In birds and insects we have the best means of studying these
phenomena, and we will now proceed to illustrate the case more
fully. The facts seem to justify us in considering that starting with
a spot we may obtain, according to the development, either an
ocellus, a stripe or bar, or a blotch, and that between, these may have
any number of intermediate varieties.

Among the butterflies we have numerous examples of the de-
velopment from spots, as illustrated in plates. A good example is
seen in our common English Brimstone (Gonepteryx rhamni) Fig. 2,
Plate III. In this insect the male (figured) is of a uniform sulphur
* SOP photographs in Hutchinson's Illustrations of Clinical Surgery.

To face paye 40.]

Plate 111.

'

BUTTERFLIES.

Spots and Stripes. 41

yellow, with a rich orange spot in the cell of each wing ; the female
is much paler in colour, and spotted similarly. In an allied con-
tinental species (G. Cleopatra) Fig. 1, Plate III., the female is like that
of rhamni only larger ; but the male, instead of having an orange
spot in the fore- wing, has nearly the whole of the wing suffused with
orange, only the margins, and the lower wings showing the sulphur
ground-tint like that of rhamni. Intermediate forms between these
two species are known. In a case like this we can hardly resist the
conclusion that the discoidal spot has spread over the fore-wing
and become a blotch, and in some English varieties of rhamni we
actually find the spot drawn out into a streak.

The family of Pieridce, or whites, again afford us admirable ex-
amples of the development of spots. The prevailing colours are
white, black and yellow : green appears to occur in the Orange-tips
(Anthocaris), but it is only the optical effect of a mixture of yellow
and grey or black scales. The species are very variable, as a rule,
and hence of importance to us ; and there are many intermediate
species on the continent and elsewhere which render the group a
most interesting study.

The wood white (Leucophasia sinapis) Fig 1, Plate IV., is a pure
white species with an almost square dusky tip to the fore- wings of
the male. In the female this tip is very indistinct or wanting,
Fig. 4, Plate IV. In the variety Diniensis, Fig. 2, Plate IV, this square
tip appears as a round spot.

The Orange-tips, of which we have only one species in Britain
(Anthocaris cardamines) belongs to a closely allied genus, as does
also the continental genus Zegris. The male Orange-tip {A.
cardamines) is white with a dark grey or black tip, and a black
discoidal spot. A patch of brilliant orange extends from the dark
tip to just beyond the discoidal spots. In the female this is wanting,
but the dark tip and spot are larger than in the male.

Let us first study the dark tip. In L. sinapis we have seen that
it extends right to the margin of the wing in the male, but in the
female is reduced to a dusky spot away from the margin, In A.
cardamines the margin is not coloured quite up to the edge, but a
row of tiny white spots, like a fringe of seed pearls, occupies the
inter-spaces of the veins. On the underside these white spots are
prolonged into short bars, see Plate IV. In the continental
species A. belemia we see the dark tip to be in a very elementary
condition, being little more than an irregular band formed of united

42 Colouration in Animals and Plants.

spots, there being as much white as black in the tip, Fig. 5, Plate IV.
In A. belia, Fig. 6, Plate IV, the black tip is more developed, and in
the variety simplonia still more so, Fig. 7, Plate IV. We here see
pretty clearly that this dark tip has been developed by the confluence
of irregular spots.

Turning now to the discoidal spot we shall observe a similar
development. Thus in : —

A. cardamines, male, it is small and perfect.

Do. female, „ larger .,

A. belemia „ large „

A, belia „ large with white centre.

Do. v. simplonia „ small and perfect.

*A. eupheno, female, „ nearly perfect.

Do. male, „ a band.

We here find two distinct types of variation. In A. belia we
have a tendency to form an ocellus, and in A. eupheno the spot of
the female is expanded into a band in the male.

The orange flush again offers us a similar case ; and with regard
to this colour we may remark that it seems to be itself a develop-
ment from the white ground-colour of the family in the direction of
the red end of the spectrum. Thus in the Black-veined white
(Aporia cratcegi) we have both the upper and under surfaces of the
typical cream-white, for there is no pure white in the family. In the
true whites the under surface of the hind-wings is lemon-yellow, in
the female of A. eupheno the ground of the upper surface is faint
lemon-yellow, and in the male this colour is well-developed. The
rich orange, confined to a spot in G. rhamni becomes a flush in G.
Cleopatra, and a vivid tip in A. cardamines. These changes are all
developments from the cream white, and may be imitated accurately
by adding more and more red to the primitive yellow, as the artist
actually did in drawing the plate.

In A. cardamines the orange flush has overflowed the discoidal
spot, as it were, in the male, and is absent in the female. But in
A. eupheno we have an intermediate state, for as the figures show, in
the female, Fig. 8, the orange tip only extends half-way to the
discoidal spot, and in the male it reaches it. Moreover it is to be
noticed that the flow of colour, to continue the simile, is unchecked
by the spot in cardamines, but where the spot has expanded to a bar in

* See Plate IV.

To face page 42,]

Plate IV.

:,HertchIy del ad nat

Spots and Stripes. 43

eupheno it has dammed the colour up and ponded it between bar and
tip. An exactly intermediate case between these two species is seen
in A. euphemoides, Fig. 10, Plate IV., in which the spot is elongated,
and dribbles off into an irregular band, into which the orange has
trickled, as water trickles through imperfect fascines. This series of
illustrations might be repeated in almost any group of butterflies,
but sufficient has been said to show how spots can spread into patches,
either by the spreading of one or by the coalescence of several.

We will now take an illustration of the formation of stripes or
bars from spots, and in doing so must call attention to the rarity of
true stripes in butterflies. By a true stripe I mean one that has even
edges, that is, whose sides are uninfluenced by structure. In all our
British species such as P. machaon, M. artemis, M. athalia, V. atalanta,
L. sibilla, A. iris, and some of the Browns, Frittilaries and Hair-
streaks, which can alone be said to be striped, the bands are clearly
nothing more than spots which have spread up to the costae, and
still retain traces of their origin either in the different hue of the
costse which intersect them, or in curved edges corresponding with
the interspaces of the costse. This in itself is sufficient to indicate
their origin. But in many foreign species true bands are found, though
they are by no means common. Illustrations are given in Plate IV.,
of two Swallow-tails, Papiiio machaon, Fig. 11, and P. podalirim
Fig 12, in which the development of a stripe can readily be seen.

In machaon the dark band inside the marginal semi-lunar spots of
the fore-wings retain traces of their spot-origin in the speckled
character of the costal interspaces, and in the curved outlines of
those parts. In podalirius the semi-lunar spots have coalesced into a
stripe, only showing its spot-origin in the black markings of the
intersecting costse; and the black band has become a true stripe,
with plain edges, Had only such forms as this been preserved, the
origin of the spots would have been lost to view.

It may, however, be said, though I think not with justice, that
we ought not to take two species, however closely allied, to illustrate
such a point. But very good examples can be found in the same
species, A common German butterfly, Araschnia Levana, has two
distinct varieties, Levana being the winter, and prorsa the summer
form ; and between these an intermediate form, porima, can be bred
from the summer form by keeping the pupae cold. Dr. Weismann,
who has largely experimented on this insect, has given accurate
illustrations of the varieties. Plate V. is taken from specimens

H

44

Colouration in Animals and Plants.

Fig. 1. Part of secondary feather of Argus Pheasant.

a. a. Elongated spots, incipient d. d. Double spots, incipient ocelli.

ocelli. e. Minute dottings.

6. Interspaces. f. f. Shaft.

c. c. Axial line. k. k. Line of feathering.

Fig. 2. Part of secondary wing feather of Argus Pheasant.

a. Oval. Axis at right angles. e. Expansion of stripe.

b. Round. f. Interspace.
c.c. Shaft, 'g. Stalk.

d. Imperfect ocellus. h. Edge of feather.

/•. Line of feathering.

To face paye 44.]

Plate V.

SEASONAL VARIETIES.

F. Skertchiy del. ad naf

Spots and Stripes. 45

in our possession. In the males of both Levana, Fig. 4, and
prorsa, Fig. 1, the hind-wing has a distinct row of spots, and a
less distinct one inside it, and in the females of both these are
represented by dark stripes. In poritna we get every intermediate
form of spots and stripes, both in the male and female, and as these
were hatched from the same batch of eggs, or, are brothers and
sisters, it is quite impossible to doubt that here, at least, we have an
actual proof of the change of spots into stripes.

The change of spots more or less irregular into eye-spots, or
ocelli, is equally clear ; and Darwin's drawing of the wings of Cyllo
leda* illustrates the point well. " In some specimens," he remarks,
" large spaces on the upper surfaces of the wings are coloured black,
and include irregular white marks ; and from this state a complete
gradation can be traced into a tolerably perfect ocellus, and this
results from the contraction of the irregular blotches of colour. In
another series of specimens a gradation can be followed from
excessively minute white dots, surrounded by a scarcely visible
black line, into perfectly symmetrical and larger ocelli." In the
words we have put in italics Darwin seems to admit these ocelli to be
formed from blotches ; and we think those of the Argus pheasant can
be equally shown to arise from spots.

Darwin's beautiful drawings show, almost as well as if made for
the purpose, that the bars are developed from spots.f In Fig. 1 is
shown part of a secondary wing feather, in which the lines k. k,
mark the direction of the axis, along which the spots ar&
arranged, perfectly on the right, less so on the left. The lengthen-
ing out of the spots towards the shaft is well seen on the right, and
the coalescence into lines on the left. In Fig. 2 we have part oi
another feather from the same bird, showing on the left elongated
spots, with a dark shading round them, and on the right double
spots, like twin stars, with one atmosphere around them. Increase
the elongation of these latter, and you have the former, and both
are nascent ocelli. We here, then, have a regular gradation
between spots, bands, and ocelli, just as we can see in insects.

In some larvae, those of the Sphingidce especially, ocelli occur, and
these may be actually watched as they grow from dots to perfect
eye-spots, with the maturity of the larva.

Even in some mammals the change from spots to stripes can be

* Desc. Man, vol. ii., p. 133, fig. 52.
t Compare his figs. 56 to 58 op. cit.

46 Colouration in Animals and Plants.

seen. Thus, the young tiger is spotted, and BO is the young lion;
but, whereas in the former case the spots change into the well-
known stripes (which are really loops), in the latter they die away.
The horse, as Darwin long ago showed, was probably descended
from a striped animal, as shown by the bars on a foal's leg. But
before this the animal must have been spotted ; and the dappled
horses are an example of this ; and, moreover, almost every horse
shows a tendency to spottiness, especially on the haunches. In the
museum at Leiden a fine series of the Java pig (Sus vittatus) is
preserved. Very young animals are banded, but have spots over
the shoulders and thighs ; these run into stripes as the animal grows
older; then the stripes expand, and, at last meeting, the mature
animal is a uniform dark brown. Enough has now, I trust, been
said upon this point to show that from spots have been developed
the other markings with which we are familiar in the animal
kingdom.

The vegetable kingdom illustrates this fact almost as well.
Thus, the beautiful leaves of the Crotons are at first green, with few
or no coloured spots ; the spots then grow more in number, coalesce,
form irregular bands, further develop, and finally cover the whole,
or almost the whole, of the leaf with a glow of rich colour. Some
of the pretty spring-flowering orchid callitriche have sulphur-yellow
petals, with dark rich sepia spots ; these often develop to such an
extent as to overspread nearly all the original yellow. Many other
examples might be given.

Hitherto we have started with a spot, and traced its develop-
ment. But a spot is itself a developed thing, inasmuch as it is an
aggregation of similarly coloured cells. How they come about may,
perhaps, be partly seen by the following considerations. Definite
colour-pattern has a definite function — that of being seen. We may,
therefore, infer that the more definite colour is of newer origin than
the less definite. Hence, when we find the two sexes differently
coloured, we may generally assume that the more homely tinted
form is the more ancient. For example, some butterflies, like the
gorgeous Purple Emperor (Apatura iris), have very sombre mates;
and it seems fair to assume that the emperor's robes have been
donned since his consort's dress was originally fashioned.

That the object of brilliant colour is display is shown partly by
the fact that in those parts of the wings of butterflies which overlap
the brilliant colour is missing, and partly by the generally brighter

Spots and Stripes. 47

hues of day-flying butterflies and moths than of the night-flying
species. Now, the sombre hues of nocturnal moths are not so much
protective (like the sober tints of female butterflies and birds),
because night and darkness is their great defender, as the necessary
result of the darkness : bright colours are not produced, because
they could not be seen and appreciated. In these cases it is very
noticeable how frequently the colour is irregularly dotted about —
irrorated or peppered over the wings, as it were. This irregular
distribution of the pigment cells, if it were quite free from any
arrangement, might be looked upon as primitive colouring, undiffer-
entiated either into distinct colour or distinct pattern. If we
suppose a few of the pigment cells here and there to become
coloured, we should have irregular brilliant dottings, just as we
actually see in many butterflies, along the costa. The grouping
together of these colour dots would give rise to a spot, from which
point all is clear.

That some such grouping or gathering together, allied to segre-
gation, does take place, a study of spots, and especially of eye-spots,
renders probable. What the nature of the process is we do not
know, nor is it easy to imagine. But let us suppose a surface
uniformly tinted brown. Then, if we gather some of the colouring
matter into a dark spot we shall naturally leave a lighter area
around it, just as we see in all our Browns and Ringlets. In this
way we can see how a ring-spot can be formed. To make it a true
eye-spot, with a light centre, we must also suppose a pushing away
of the colour from that centre. A study of ocelli naturally suggests
such a process, which is analogous to the banding of agates, and all
concentric nodules. Darwin, struck with this, seems to adopt it as
a fact, for he says, " Appearances strongly favour the belief that, on
the one hand, a dark spot is often formed by the colouring matter
being drawn towards a central point from a surrounding zone, which
is thus rendered lighter. And, on the other hand, a white spot is
often formed by the colour being driven away from a central point,
so that it accumulates in a surrounding darker zone."* The analogy
between ocelli and concretions may be a real one. At any rate beauti-
ful ocelli of all sizes can be seen forming in many iron-stained sand-
stones. The growth of ocelli may thus be a mechanical process
adapted by the creature for decorative purposes, but the artistic
colouring of many eye-spots implies greater effort.

* Desc. Man, vol. ii., p. 134.

48 Colouration in Animals and Plants.

There is, however, one set of colour lines in birds and insects
that do not seern to arise from spots in the ordinary way. These
are the coloured feather-shafts of birds, and the coloured nerves or
veins in a butterfly's wing, In these the colour has a tendency to
flow all along the structure in lines.

Conclusion. The results arrived at in this chapter may be thus
summarised : —

Spots, ocelli, stripes, loops, and patches may be, and nearly
always are, developed from more or less irregular spots.

This is shown both by the study of normal colouring, or by
abnormal colouring, or decolouring in disease.

Even the celebrated case of the Argus Pheasant shows that
the bands from which the ocelli are developed arose from spots.

CHAPTER VII.
COLOURATION IN THE INVERTEBRATA.

IF the principle of the dependence of colour-pattern upon struc-
ture, enunciated in the preceding pages be sound, we ought to
find certain great schemes of colouration corresponding to the great
structural subdivisions of the animal kingdom. This is just what we
do find; and before tracing the details, it will be as well to group
the great colour-schemes together, so that a general view of the
question can be obtained at a glance.

The animal kingdom falls naturally into two divisions, but the
dividing line can be drawn in two ways. If we take the most
simple classification, we have : —

1. Protozoa, animals with no special organs.

2. Organozoa, animals possessing organs.

Practically this classification is not used, but we shall see that
from our point of view it is a useful one. In the most general
scheme the divisions are : —

1. Invertebrata, animals without backbones.

2. Vertebrata, animals with backbones.

The invertebrata are divided into sub-kingdoms, of which the
protozoa form one. These protozoa possess, as it were, only negative
properties. In their simplest form they are mere masses of proto-
plasm, even lacking an investing membrane or coat, and never,
even in the highest forms, possessing distinct organs. It is this
simplicity which at once separates them entirely from all other
animals.

50 Colouration in Animals and Plants.

The other sub-kingdoms are : —

Ccelenterata, of which the jelly-fishes are a type ; animals possessing
an alimentary canal, fully communicating with the general cavity of
the body, but without distinct circulatory or nervous systems.

A nnuloida, of which the star-fishes are a type ; animals having the
alimentary canal shut off from the body-cavity, and possessing a
nervous system, and in some a true circulatory system.

Annulosa, of which worms, lobsters, and insects are types; animals
composed of definite segments, arranged serially, always possessing
true circulatory and nervous systems.

Mollusca, of which oysters and whelks are types ; animals which
are soft-bodied, often bearing a shell, always possessing a distinct
nervous system and mostly with a distinct heart.

In old systems of classification, the Coelenterata and Annuloida
were united into one sub-kingdom, the Radiaia, in consequence of
their radiate or star-like structures.

As colouration, according to the views here set forth, depends
upon structure, we may classify the Invertebrata thus : —

Protozoa ... ... ... Structureless.

Coelenterata )
. i • i r ... Radiata. Radiate structure.

Annulosa Segmented „

Mollusca Margiiiate „

The mollusca are said to be marginate in structure because, in those
possessing shells — the mollusca proper — the shell is formed by suc-
cessive additions to the margin or edge of the shell, by means of the
margin of the mantle, or shell-secreting organ.

Now we shall proceed to show that the schemes of colouration
follow out these structure-plans, and thus give additional force to
the truth of the classification, as well as showing that, viewed on a
broad scale, the present theory is a true one.

We can, in fact, throw the whole scheme into a table, as
follows : —

Colouration in the fnverfebrata.

51

SYSTEMS. OF COLOURATION.

System of Colouring.

Structure.

Sub-kingdoms.

A. No Axial Decoration.

A. No Axial Structure.

A. Invertebrata.

1.

2.
3.

4.

No definite system.
Radiate system.
Segmental system.
Marginate system.

No definite organs.
Radiate structure.
Segmental structure.
Marginate growth.

Protozoa.
Coelenterata, Atmuloida.
Annulosa.
Mollusca.

B. Axial Decoration.

B. Axial Structure.

B. Vertebrata.

5.

Axial system.

Axial structure.

Vertebrata.

Protozoa. The protozoa are generally very minute, and always
composed of structureless protoplasm. Their peculiarities are rather
negative than positive, there being neither body segments, muscular,
circulatory, nor nervous systems. Even the denser exterior portion
(ectosarc) possessed by some of them seems to be rather a temporary
coagulation of the protoplasm than a real differentiation of that
material.

Here, then, we have to deal with the simplest forms of life, and if
colouration depends upon structure, these structureless transparent
creatures should lack all colour-pattern, and such is really the case.
Possessing no organs, they have no colouration, and are generally
either colourless or a faint uniform brown colour, and through their
colourless bodies the food particles show, often giving a fictitious
appearance of colouring.

To this general statement there is a curious and most telling ex-
ception. In a great many protozoa there exists a curious pulsating
cell-like body, called the contractile vesicle, which seems to be a
rudimentary organ, whose function is unknown. Here, then, if
anywhere, traces of colouring should be found, and here it is
accordingly found, for, though generally clear and colourless, it
sometimes assumes a pale roseate hue. This may be deemed the
first attempt at decoration in the animal kingdom, and it is directly
applied to the only part which can be said to possess structure.
Beautiful examples are plentiful in Leidy's magnificient volume on
Freshwater Rhizopods.

Ccelenterata. These animals fall into two groups, the Hydrozoa,
of which the hydra and jelly-fishes are types, and the Actinozoa, of
which the sea-anemonies and corals are types. Most of the coslen-

I

52 Colouration in Animals and Plants.

terata are transparent animals, but it is amongst them we first come
across opaque colouring.

Of the lowest forms, the hydras, nothing need be said here, as
they are so much like the protozoa in their simplicity of structure.

The Corynida, familiar to many of our sea-side visitors by their
horny brown tubes (Tubularia), attached to shells and stones, are
next in point of complexity. Within the tube is found a semi-fluid
mass of protoplasm, giving rise at the orifice to the polypite, which
possesses a double series of tentacles. These important organs are
generally of a vivid red colour, thus emphasizing their importance
in the strongest manner. Other members of the order are white,
with pink stripes.

In the larval stage many of the animals belonging to the above
and allied orders, are very like the true jelly-fishes. These free
swimming larvse, or gonop/iores, possess four radiating canals, passing
from the digestive sac to the margins of the bell, and these are often
the seat of colour. In these creatures, too, we find the earliest
trace of sense organs, and consequently, the first highly differen-
tiated organs, and they appear as richly coloured spots on the
margins of the bell. The true oceanic Hydrozoa again afford us
fine examples of structural colouration. The beautiful translucent
blue-purple Velella, which is sometimes driven on to our shores, is a
case in point ; and its delicate structure lines are all emphasized in
deeper hues. The true jelly-fishes (Medusidce) with their crystal
bells and radiating canals, frequently show brilliant colour, and it is
applied to the canals, and also to the rudimentary eye-specks, which
are frequently richly tinted, and in all cases strongly marked. In
the so-called "hidden-eyed" Medusae we find the same arrangement
of colour, the same emphasized eye-specks, and the reproductive
organs generally appear as a vivid coloured cross, showing through
the translucent bell.

Turning now to the Actinozoa, of which the sea anemonies and
corals are types, we are brought first into contact with general
decorative, more or less opaque colour, applied to the surface of the
animal. In the preceding cases the animals have been almost
universally transparent or translucent, and the colouration is often
applied to the internal organs, and shows through. In the sea-
anemonies we find a nearer approach to opacity, in the dense
muscular body, though even this is often translucent, and the
tentacles generally so, often looking like clouded chalcedony. The

Colouration in the Invertebrata. 53

wealth of colour to be found in these animals gives us a very
important opportunity of studying decoration, where it first appears
in profusion.

One of the first points that strikes even a casual observer is that
amongst the sea-anemonies the colouration is extremely variable,
even in the same species and in the same locality. This is in
strong contrast to what we generally find amongst the higher
organisms, such as insects and birds ; for though considerable
variation is found in them, it does not run riot as in the anemonies.
It would almost appear as if the actual colour itself was of minor
importance, and only the pattern essential ; the precise hue is not
fixed, is not important, but the necessity of colour of some sort
properly arranged is the object to be attained. Whether this idea
has a germ of truth in it or not, it is hard to say, but when we take
the fact in connection with its occurrence just where opacity begins,
connecting this with the transparency of the lower organisms, and
the application of vivid colour to their internal organs, one seems
to associate the instability of the anemony's colouring with the
transference of colour from the interior to the exterior. Certain it
is, that vivid colour never exists in the interior of opaque animals ;
it is always developed under the influence of light. The white
bones, nerves and cartilages, and the uniform red of mammalian
muscles, are not cases of true decorative colouring in our sense of
the term, for all bodies must have some colour. All bone is practi-
cally white, all mammalian muscle red, but for these colours to be
truly decorative, it would be necessary for muscles of apparently
the same character often to be differently tinted, just as the
apparently similar hairs on a mammal, and scales on an insect, are
variously painted. This we do not find, for the shaft-bones and
plate-bones, and even such odd bones as the hyoid are all one
colour ; and no one would undertake to tell, by its hue, a piece of
striped from a piece of unstriped muscle. Decorative colouring
must be external in an opaque animal ; it may be internal in a
transparent one.

The connection thus shown between decoration and transparency
seems to suggest that hypodermal colour is the original, and
epidermal the newer scheme : that the latter was derived from the
former. This agrees with Haagen's shrewd hint that all mimetic
colour was originally hypodermal. Certain it is that the protective

54 Colouration in Animals and Plants.

colour that is still under personal control, as in the chameleon, &c.,
is always hypodermal.

The common crass (Bunodes crassicornis) is so extremely variable,
that all one can say of it is, that it is coloured red and green. But
this colour is distributed in accordance with structure. The base,
or crawling surface, not being exposed to the light, is uncoloured.
The column, or stem, is irregularly spotted, and striped in accord-
ance with the somewhat undifferentiated character of its tissue, but
the important organs, the tentacles, are most definitely ornamented,
the colour varying, but the pattern being constant. This pattern
is heart-shaped, with the apex towards the point of the tentacle ;
that is to say, the narrow part of the pattern points to the narrow
part of the tentacle.

In the common Actinea mesembryanthemum, which is often blood red,
the marginal bodies, probably sense-organs, are of the most exquisite
turquoise blue colour, and the ruby disc thus beaded is as perfect an
example of simple structural decoration as could be desired. A zone
of similiar blue runs round the base of the body.

Turning now to the corals, which are simply like colonies of
single anemonies with a stony skeleton, we have quite a different
arrangement of hues. No sight is more fascinating than that of a
living-coral reef, as seen through the clear waters of a lagoon. The
tropical gardens ashore cannot excel these sea-gardens in brilliancy
or variety of colour, Reds, yellows, purples, browns of every shade,
almost bewilder the eye with their profusion ; and here again we find
structural decoration carried out to perfection. The growing points
of white branching corals (Madrepores) are frequently tipped with
vivid purple, and the tiny polyps themselves are glowing gem-stars.
In the white brain-corals, the polyps are vivid red, green, yellow,
purple and so on ; but in almost every case vividly contrasting with
the surrounding parts, the colour changing as the function changes.

The Alcyonarice, which include the sea-fans, sea-pens, and the red
coral of commerce, practically bring us to the end of the Coslenterata,
and afford us fresh proof of the dependence of colour upon structure
and function. The well-known organ-pipe coral (Ttibipora musica)
is of a deep crimson colour, and the polyps themselves are of the
most vivid emerald green, a contrast that cannot be excelled.
Almost equally beautiful is the commercial coral (Corallium rubrum)
whose vivid red has given a name to a certain tint. In this coral the
polyps are of a milk-white colour.

Colouration in the Invertebrata. 55

It must be remembered that in these cases the colour seems
actually to be intentional, so as to form a real and not merely an
accidental contrast between the stony polypidom and the polyp, for
the connecting tissue (coenosarc) is itself as colourless as it is
structureless.

Gathering together the facts detailed in this chapter we find : —

1. That the Protozoa are practically colourless and structureless.

2. That in those species which possess a rudimentary organ
(contractile vescicle) a slight decoration is applied to that
organ.

3. That in the Coelenterata the colouration is directly dependent

upon the structure.

4. That in transparent animals the colouration is applied directly

to the organ whether it be internal as in the canals or
ovaries, or external, as in the eye-specks.

5. That in opaque animals, as in the sea-anemonies, the colouring

is entirely external.

6. That it is very variable in hue, but not in pattern.

7. That the most highly differentiated parts (tentacles, eye-

specks), are the most strongly coloured.

8. That in the corals an emphatic difference occurs between the

colour of the polypidom (or " coral ") and the polyp.

T

CHAPTER VIII.

DETAILS OF PROTOZOA.
HE Protozoa are divided into three orders.

I. — Gregarinidce.
II. — Rhizopoda.
III. — Infusoria.

I. The GregannidcB consist of minute protozoa, parasitic in the
interior of insects, &c., and like other internal parasites are colour-
less, as we should expect.

II. The Rhizopoda may, for our purpose, be divided into the
naked forms like Amoeba, and those which possess a skeleton, such as
the Radiolaria, the Foraminifera and the Spongia.

Of these the naked forms are colourless, or uniformly tinted,
excepting the flush already described as emphasizing the contractile
vesicle.

The Foraminifera are the earliest animals that possess a skeleton
or shell, and though generally very small, this shell is often complex,
and of extreme beauty, though their bodies retain the general sim-
plicity of the protozoa, indeed, they are said to possess no contractile
vesicle. Still the complexity of their shells places them on a
higher level than the naked rhizopoda.

In these animals we find the first definite colour, not as a pattern,
but as simple tinting of the protoplasm. The general hue is
yellowish-brown (as in Amoeba), but deep red is not uncommon. The
deepest colour is found in the oldest central chambers, becoming
fainter towards the periphery, where it is often almost unrecog-
nisable.*

* Lcidy. Rhizopoda of N. America, p. 16.

Details of Protozoa. 57

The Radiolaria are minute organisms with still more complex
skeletons, and are considered by Haeckel * to be more highly organ-
ized than the preceding order. They consist of a central portion
containing masses of minute cells, and an external portion containing
yellow cells. Here we have the first differentiation of parts in the
external coating and internal capsule, and side by side with this
differentiation we find colour more pronounced, and even taking
regional tints in certain forms.

We may notice the following genera as exhibiting fine colour : —

Red. Eucecryphalus, Arachnocorys, Eucrytidium, Dictyoceras
Yellow. Carpocanium, Dictyophimus, Amphilonche.
Purple. Eucrytidium, Acanthostratus.
Bine. Cyrtidospheera, Coelodeiidrum.
Green. Cladococeus, Amphilonche.
Brown. Acanthometra, Amphilonche.

Examples of these may be seen in the plates of Haeckel's fine
work, and as an illustration of regional decoration we cite Acanthos-
tratus purpuraceus, in which the central capsule is seen to run from
red to orange, and the external parts to be colourless, with red mark-
ings in looped chains.

Spongocyclia also exhibits this regional distinction of colour very
clearly, the central capsule being red and the external portion yellow.

The Spongida, or sponges, are, broadly speaking, assemblages
or colonies of amoeba-like individuals, united into a common society.
Individually the component animals are low, very low, in type, but
their union into colonies, and the necessity for a uniform or common
government has given rise to peculiarities that in a certain sense
raise them even above the complex radiolaria. Some, it is true, are
naked, and do not possess the skeleton that supports the colony,
which skeleton forms what we usually call the sponge ; but even
amongst these naked sponges the necessity for communal purposes
over and above the mere wants of the individual, raises them a step
higher in the animal series. A multitude of individuals united by a
common membrane, living in the open sea, it must have happened
that some in more immediate contact with the food-producing waters,
would have thriven at the expense of those in the interior who
could only obtain the nutriment that had passed unheeded by the peri-
pheral animals. But just as in higher communities we have an

* Haeckel Die Kadiolarien, Berlin, 1862.

58 Colouration in Animals and Plants.

inflowing system of water and an out-flowing system of effete
sewerage quite uncontrolled, and, alas, generally quite unheeded by
the individuals whose wants are so supplied ; so in the sponges we
have a system of inflowing food-bearing water and an out-flowing
sewage, or exhausted-water system. This is brought about by a
peculiar system of cilia-lined cells which, as it were, by their motion
suck the water in, bringing with it the food, and an efferent system
by which the exhausted liquid escapes. These cilia-lined cells are the
first true organs that are to be found in the animal kingdom, and
according to the views we hold, they ought to be emphasized with
colour, even though their internal position renders the colouration
less likely. This we find actually to be the case, and these flagel-
lated cells, as they are called, are often the seat of vividest colour.

The animal matter, or sarcode, or protoplasm of sponges falls
into three layers, just as we find the primitive embryo of the highest
animals ; and just as the middle membrane of a mammalian ovum
develops into bone, muscle and nerve, so the middle membrane
(mesosarc) of the sponges develops the hard skeleton, and in this
most important part we find the colour cells prevail. Sollas, one of our
best English authorities upon sponges, writes, " The colours of
sponges, which are very various, are usually due to the presence of
pigment granules, interbedded either in the endosarc of the flagellated
cells, or in the mesodermic cells, usually of the skin only, but some-
times of the whole body." *

We can, then, appeal most confidently to the protozoa as illus-
trating the morphological character of colouration.

* Sollas. Spongidse. Cassell's Nat. Hist. Vol. vi., p. 318.

CHAPTER IX.

DETAILS OF CCELENTERATA.

I. HYDROZOA.

A. Hydrida.

THE Hydras, as a rule, are not coloured in our sense of the term ;
that is to say, they are of a general uniform brown colour.
But in one species, H. viridis, the endoderm contains granules of a
green colour, which is said to be identical with the green colouring
matter of leaves (chlorophyll). This does not occur in all the cells,
though it is present in most. The green matter occurs in the form
of definite spherical corpuscles, and these colour-cells define the
inner layer of the integument (the endoderm), and render it distinct.*
That portion of the endoderm which forms the boundary of the body-
cavity has fewer green corpuscles, but contains irregular brown
granules, thus roughly mapping out a structural region.

We thus see that even in so simple a body as the Hydra the
colouring matter is distributed strictly according to morphological
tracts.

B. Tubularida. The Tubularian Hydroids are the subject of an
exhaustive and admirably illustrated monograph by Prof. J. Allman,
from which the following details are culled. These animals are with
few exceptions marine, and consist either of a single polypite or of a
number connected together by a common flesh, or coenosarc. Some
are quite naked, others have horny tubes, into which, however, the
polypites cannot retreat. The polypites consist essentially of a sac
surrounded with tentacles ; and one of their most striking characters

* Allman's Hydroids. Bay. Soc., p. 123.

K

60 Colouration in Animals and Plants.

is their mode of reproduction. Little buds (gonophores) grow from
the coenosarc, and gradually assume a form exactly like that of a
jelly-fish. These drop off, and swim freely about ; and are so like
jelly-fishes that they have been classed among them as separate
organisms.

The Tubularise are all transparent ; and in them we find
structural colouration finely shown, the colour, as is usual in
transparent animals, being applied directly to the different organs.

Writing of the colour, Prof. Allman says : " That distinct
secretions are found among the Hydroida, and that even special
structures are set aside for their elaboration, there cannot now be
any doubt.

" One of the most marked of these secretions consists of a
coloured granular matter ; which is contained at first in the interior
of certain spherical cells, and may afterwards become discharged
into the somatic fluid. These cells, as already mentioned, are
developed in the endoderm ;* in which they are frequently so abun-
dant as to form a continuous layer upon the free surface of this
membrane. It is in the proper gastric cavity of the hydranth and
medusa, in the spadix of the sporosac, and in the bulbous dilatations
which generally occur at the bases of the marginal tentacles of the
medusee, that they are developed in greatest abundance and
perfection ; but they are also found, more or less adundantly, in the
walls of probably the whole somatic cavity, if we except that portion
of the gastrovascular canals of the medusa which is not included
within the bulbous dilatations.

" In the parts just mentioned as affording the most abundant
supply of these cells, they are chiefly borne on the prominent ridges
into which the endoderm is thrown in these situations ; when they
occur in the intervals between the ridges they are smaller, and less
numerous.

" The granular matter contained in the interior of these cells
varies in its colour in different hydroids. In many it presents
various shades of brown ; in others it is a reddish-brown, or light
pink, or deeper carmine, or vermilion, or orange, or, occasionally, a
fine lemon-yellow, as in the hydranth of Coppinia arcta, or even a
bright emerald green, as in the bulbous bases of the marginal
tentacles of certain medusas. No definite structure can be detected
in it ; it is entirely composed of irregular granules, irregular in form,

* Compare with Hydra above.

Details of Ccelenterata. 61

and usually aggregated into irregularly shaped masses in the interior
of the cells. It is to this matter that the colours of the Hydroida,
varying, as they do, in different species, are almost entirely due.

" The coloured granular matter is undoubtedly a product of true
secretion ; and the cells in which it is found must be regarded as true
secreting cells. These cells are themselves frequently to be seen as
secondary cells in the interior of parent cells, from which they
escape by rupture, and then, falling into the somatic fluid, are carried
along by its currents, until, ultimately, by their o\vn ruptuie, they
discharge into it their contents.

"We have no facts which enable us to form a decided opinion as
to the purpose served by this secretion. Its being always more or
less deeply coloured, and the fact of its being abundantly produced
in the digestive cavity, might suggest that it represented the biliary
secretion of higher animals. This may be its true nature, but as yet
we can assert nothing approaching to certainty on the subject;
indeed, considering how widely the cells destined for the secretion
of coloured granules are distributed over the walls of the somatic
cavity, it would seem not improbable that the import of the coloured
matter may be different in different situations ; that while some of it
may be a product destined for some further use in the hydroid, more
of it may be simply excretive, taking no further part in the vital
phenomena, and intended solely for elimination from the system."*

Here we have very definite statements by a highly trained
observer of the distribution of colour iii the whole of these animals,
and of the conclusions he draws from them.

Firstly as to the colour itself. We find it true colour — brown,
pink, carmine, vermilion, orange, lemon-yellow, and even emerald
green ; a set of hues as vivid as any to be found in the animal
kingdom. It is difficult to conceive these granules to be merely
excrementitious matter ; for in such simple creatures, feeding upon
such similar bodies, one would hardly expect the excretive matter to
be so diversified in tint. Moreover, excrementitious matter is not,
as a rule, highly coloured, but brown. Thus, we see in the
Rhizopods the green vegetable matter which has been taken in as
food becomes brown as the process of assimilation goes on ; and,
indeed, colour seems almost always to be destroyed by the act of
digestion.

Still, it by no means follows that this colour, even if it is

* Allman. Monograph of Tubularian Hydroida. Bay. Soc., p. 135.

62 Colouration in Animals and Plants.

produced for the sake of decoration, as we suggest, may not owe its
direct origin to the process of digestion. The digestive apparatus
is the earliest developed in the animal kingdom, and in these
creatures is by far the most important; the coelenterata being, in
fact, little more than living stomachs. If, then, colouration be
structural, what is more likely than that the digestive organs should
be the seat of decoration in such transparent creatures ?

Secondly, as to the distribution of the colour. We find it
" frequently forming a continuous layer upon the free surface of "
the endoderm, in the " spadix of the sporosac," and in the " bulbous
terminations " of the canals, that colour is best developed. In other
words, the colour is distributed structurally, and is most strongly
marked where the function is most important.

Prof. Allman gives no hint that the colour may be purely
decorative, and is naturally perplexed at the display of hues in such
vigour ; but if this be one of the results of the differentiation of parts,
of the specialization of function, then we can, at least, understand
why we find such brilliant colour in these creatures, and why it is so
distributed.

As an illustration of the Tubularia we have selected Syncoryne
pulchella, Fig. 2, PI. VI., and its medusa, Fig. 1. The endoderm
of the spadix of the hydranths is of a rich orange colour, which
becomes paler as it descends towards the less highly organized
stem. Medusae are seen in various stages of development, and one,
mature and free, is shown. In these the manubrium, and the
bulbous terminations of the canals are also seen to be coloured
orange.

In these medusa? we find the first appearance of sensory organs.
They consist of pigment-cells enclosed in the ectoderm, or outside
covering ; and are singular as presenting the first true examples of
opaque colouring in the animal kingdom. They are associated with
nerve cells attached to a ring of filamentous nerve matter, surround-
ing the base of the bell. In some important respects the pigment
differs from that in other parts of the animal. It is more definite in
structure ; and the whole ocellus is " aggregation of very minute
cells, each filled with a homogeneous coloured matter."* These
ocelli, and similar sense organs, called litlwcysts, are always situated
over the bulbous termination of the canals. The pigment is black
(as in this case), vermilion, or deep carmine.

* Allman, op. cit., p. 139.

To face paye 62.]

Plate VI.

SYNCORYNE PULCHELLA.

RE .Skertchiy del.

Details of Coelenterata. 63

The dependence of colour upon structure is thus shown to hold
good throughout these animals in a most remarkable manner, and
the acceptance of the views here set forth gives us an insight into
the reasons for this colouration which, as we have seen, did not
arise from the study of the question from the ordinary point of
view.

C. Sertularida. These animals are very similar to the last, but
they are all compound, and the polypites can be entirely withdrawn
within the leathery investment or polypary. Their mode of repro-
duction is also similar, and their colouration follows the same
general plan. Being so like the preceding order, it is unnecessary
to describe them.

B. Siphonophora.

The Siphonophora are all free-swimming, and are frequently
called Oceanic Hydrozoa. They are divided into three orders,
viz: —

a. Calycoplwridce.

b. Physophoridcp.

c. Medusidce.

a. Calycophoridce. These animals have a thread-like coenosarc,
or common protoplasm, which is unbranched, cylindrical, and con-
tractile. They are mostly quite transparent, but where colour exists
it is always placed structurally. Thus, in Diphyes the sacculi of the
tentacles are reddish, in Sphceronectes they are deep red, and in Abyla
the edges of the larger specimens are deep blue."*

b. Physophoridce. These creatures are distinguished by the
presence of a peculiar organ, the float, or pneumatopliore, which is a
sac enclosing a smaller sac. The float is formed by a reflexion of
both the ectoderm and endoderm, and serves to buoy up the animal
at the surface of the sea. The best known species is the Physalia,
or Portuguese Man-o'-War.

Prof. Huxley, in his monograph on the Oceanic Hydrozoa, gives
many details of the colouration ; and, not having had much oppor-
tunity of studying them, the following observations are taken from
his work. It will be seen that the Physophoridae illustrate the
structural distribution of colour in a remarkable manner.

Stephanomia amphitridis. the hydrophyllia, colourless, and so

* Huxley. Oceanic Hydrozoa, pp. 32, 46, 50.

64 Colouration in Animals and Plants.

transparent as to be almost imperceptible in water, coenosarc
Avhitish, enlarged portions of polypites, pink or scarlet, sacs of
tentacles scarlet.

The enlarged portion of the polypites is marked with red stria?,
" which are simply elevations of the endoderm, containing thread-
cells and coloured granules." The small polypites do not possess
these elevations, and are colourless.

Agalma breve, like a prismatic mass of crystal, with pink float and
polypites.

AthoryUa rosacea, float pink, with radiating dark-brown striae,
made up of dots ; polypites lightish red, shading to pink at their
apices ; tentacles yellowish or colourless, with dark-brown sacculi ;
thread-cells dark brown.

Rldzophysa filiformis, pink, with deep" red patcli surrounding the
aperture of the pneumatocyst.

Physalia caravilla, bright purplish-red, with dark extremities, and
blue lines in the folds of the crest ; polypites violet, with whitish
points, larger tentacles red, with dark purple acetabula, smaller
tentacles blue, bundles of buds reddish.

P. pelagica, in young individuals pale blue, in adult both ends
green, with highest part of crest purple, tentacles blue, with dark
acetabula ; polypites dark blue, with yellow points.

P. utriciilus. Prof. Huxley describes a specimen doubtfully
referred to this species very fully, as follows : —

" The general colour of the hydrosoma is a pale, delicate green,
passing gradually into a dark, indigo blue, on the under surface.

" The ridge of the crest is tipped with lake, and the pointed end
is stained deep bluish-green about the aperture of the pneumato-
cyst.

" The bases of the tentacles are deep blue ; the polypites deep
blue at their bases, and frequently bright yellow at their apices ; the
velvetty masses of reproductive organs and buds on the under
surface are light green."

He further remarks that the tentacles have reniform thickenings
at regular intervals, and " the substance of each thickening has a
dark blue colour, and imbedded within it are myriads of close-set,
colourless, spherical thread-cells."

It would not be possible to find a more perfect example of
regional colouration. Not only is each organ differently coloured,

Details of Ccelenterata. 65

but the important parts of eacli organ, like the ridge of the crest,
the bases of the tentacles, and the thread-cell bearing ridges of the
tentacles, are also emphasized with deep colour.

Velella. This beautiful creature, which sometimes finds its way
to our shores, is like a crystal raft fringed with tentacles, and having
an upright oblique crest, or sail. The margins of the disk and crest
are often of a beautiful blue colour, and the canals of the disk become
deep blue as they approach the crest. The polypites may be blue,
purple, green, or brown.

C. Medusidce. The structure and colouration of the true Medusae
are so like that of the medusiform larvae of the other Hydrozoa, that
they need not be particularly described.

I}. Lucernarida. Of this sub-class we need only cite the Lucer-
naria themselves ; which are pretty bell-shaped animals, having the
power of attaching themselves to seaweeds, etc., and also of swim-
ming freely about. Round the margin are eight tufts of tentacles,
opposite eight lobes, the membrane between the lobes being
festooned. In L. auricula, a British species, the membrane is colour-
less and transparent, the lobes bright red, or green, and the
tentacles blue.

As a group the Hydrozoa display regional colouration in a very
perfect manner.

II. ACTINOZOA.

It is not necessary to trace the colouration through all the
members of this group, but we will trace the variation of colour
through two species of anemonies, which have been admirably
studied by Dr. A. Andres.* The first column shows the general hue,
the second the tints of that hue which are sufficiently marked to
form varieties as cochineal red, chocolate, bright red, rufous, liver-
coloured, brown, olive, green and glaucous. The third column gives
the spotted varieties, from which it will be seen that the choco-
late, liver, and green coloured forms have each coloured varieties.
It will be seen that the range of colour is very great, passing from
pale pink, through yellowish-brown to blue-green.

* Fauna und Flora des Golfes von Neapel. Die Actinien. 1884.

66

Colouration in Animals and Plants.

Prevailing
colour.

Uniform
varieties.

Spotted
varieties.

Allied species.

White.

0

A. Candida.

is

coccinea.

chiocca.

tigrina.

Bed.

rubra.

(j

rufosa.

Yellow.

hepatica.

fragacea.

»

umbra.

»

olivacea.

viridis.

opora.

>»

glaucus.

Blue.

?

Varieties of Actinea Cari.

The following brief descriptions illustrate the distribution of
the colour : —

Actinea Cari.
Uniform varieties (Homochroma).

Column.

Tentacles.

Gonidia.

Zone.

a. Hepatica . .
)8. Rubra ..
y. Chiocca ..
8. Coccinea ..
t. Olivacea ..
£. Viridis . .

red brown,
crimson,
scarlet,
cochineal,
olive-brown green,
green.

azure,
violet,
white,
yellowish,
azure,
azure.

azure.

azure,
azure.

azure.

( wanting, or
( flesh coloured.

azure.

Spotted varieties (ffeterochroma).

TI. Tigrina ...
9. Fragacea ...

». Opora

red, spotted yellow
liver, spotted clear
green,
green spotted, and
striped yellow

azure or white,
azure.

indistinct.

In this table the varieties above mentioned are further par-
ticularized. The column is the stalk or body, the tentacles are the
arms, the gonidia the eye spots, and the zone the line round the base.
It will be noticed that these regions are often finely contrasted in
colour.

Bunodes gemmaceus is another variable form, and the following
varieties are recognised.

Details of Ccelenterata. 67

ffeterochroma.
a. Ocracea, I peristome ochre yellow, zone black, tentacles grey,

with blue and white spots.
/3. Pallida, peristome whitish grey unhanded, tentacles with

white spots.
y. Viridescens, peristome greenish white unhanded, tentacles

with white spots and rosy shades.
S. Aurata, column at base golden, peristome intenser yellow

with crimson flush, tentacles grey with ochreous and white

spots.
«. Carnea, column at base flesh coloured, peristome rosy, tentacles

rosy, with white spots.

Homoc hroma.

£. Eosea, like e, but with rosy tubercles.

r). Nigricans, peristome blackish, with blue and green reflexions
(riftessi).

A few other examples may be given, all of which can be studied
in Dr. Andre's magnificently coloured plates.

Aiptasia mutdbilis is yellow brown, the tentacles spotted in
longitudinal rows, the spots growing smaller towards the tip, thus
affording a perfect example of the adaptation of colour to structure.

Anemonia sulcata has normally long light yellow pendulous
tentacles tipped with rose, but a variety has the column still yellow
but the tentacles pale green, tipped with rose.

Bunodes rigidus has the column green, with rows of crimson
tubercles, the tentacles are flesh-coloured, except the outer row
which are pearly ; the peristome is green, with brown lips.

CHAPTER X.

THE COLOURATION OF INSECTS.

IN the decoration of insects and birds, nature has exerted all her
power ; and amongst the wealth of beauty here displayed we
ought to find crucial tests of the views herein advocated. It will
be necessary, therefore, to enter somewhat into detail, and we shall
take butterflies as our chief illustration, because in them we find the
richest display of colouring. The decoration of caterpillars will
also be treated at some length, partly because of their beauty, and
partly because amongst them sexual selection cannot possibly
have had any influence.

Butterflies are so delicate in structure, so fragile in constitution,
so directly affected by changes of environment, that upon their
wings we have a record of the changes they have experienced,
which gives to them a value of the highest character in the study of
biology. In them we can study every variation that geographical
distribution can effect ; for some species, like the Swallow-tail
(Papilio machaori) and the Painted Lady (Cynthia cardui), are almost
universal, and others, like our now extinct Large Copper (Lycccna
dispar), are excessively local, being confined to a very few square
miles. From the arctic regions to the tropics, from the mountain
tops to the plains, on the arid deserts and amidst luxuriant vege-
tation, butterflies are everywhere to be found.

Before entering into details, it will be as well to sketch some of
the broad features of butterfly decoration. In the first place they
are all day-fliers, arid light having so strong an influence upon
colour, there is a marked difference in beauty between them and the
night-flying moths. A collection of butterflies viewed side by side
with a collection of moths brings out this fact more strongly than

The Colouration of Insects. 69

words can describe, especially when the apparent exceptions are
considered ; for many moths are as brightly coloured as butterflies.
These will be found to belong either to day-flying species, like the
various Burnets (Zygcena), Tiger Moths (Arctia), or evening flyers
like the Hawk Moths (Sphyngidce.) The true night-flying, darkness-
loving moths cannot in any way compare with the insects that
delight in sunshine. We see the same thing in birds, for very few
nocturnal species, so far as we are aware, are brilliantly decorated.

Another salient feature is the difference that generally exists
between the upper and lower surfaces of the wings. As a rule, the
upper surface is the seat of the brightest colour. Most butterflies,
perhaps all, close their wings when at rest, and the upper wing is
generally dropped behind the under wing, so that only the tip is
visible. The under surface is very frequently so mottled arid
coloured as to resemble the insect's natural surroundings, and so
afford protection. It does not follow that this protective colouring
need be dull, and only when we know the habit of the insect can we
pronounce upon the value of such colouring. The pretty Orange-
tip has its under wings veined with green, and is most conspicuous
in a cabinet, but when at rest upon some umbelliferous plant, with
its orange tip hidden, these markings so resemble the environment
as to render the insect very inconspicuous. The brilliant Argynnis
Lathonia, with its underside adorned with plates of metallic silver, is
in the cabinet a most vivid and strongly-marked species; but we
have watched this insect alight among brown leaves, or on brown
stones, outside Florence, where it is very common, and find that
these very marks are a sure protection, for the insect at rest is
most difficult to see, even when it is marked down to its resting-
place.

But some butterflies have parts of the under surface as gaily
decorated as the upper ; and this not for protection. This may be
seen to some extent in our own species, for instance in the orange-
tip of the Orange-tip, and the red bar in the upper wing of the Red
Admiral (V. atalanta}. If we watch these insects, the conviction that
these are true ornaments is soon forced upon us. TJie insect alights,
perhaps alarmed, closes its wings, and becomes practically invisible.
With returning confidence it will gradually open its wings and
slowly vibrate them, then close them again, and lift the upper wing
to disclose the colour. This it will do many times running, and the
effect of the sudden appearance and disappearance of the bright

70

Colouration in Animals and Plants.

hues is as beautiful as it is convincing. None can doubt the love
of display exhibited in such actions.

The delicacy of their organization renders butterflies peculiarly
susceptible to any change, and hence they exhibit strong tendencies
to variation, which make them most valuable studies. Not only do
the individuals vary, but the sexes are often differently coloured.
Where two broods occur in a season they are sometimes quite
differently decorated, and finally a species inhabiting widely different
localities may have local peculiarities.

We can thus study varieties of decoration in many ways, and we
shall treat of them as follows : —

1. Simple Variation, in which the different individuals of a

species vary in the same locality.

2. Local Variation, in which the species has marked peculiarities

in different localities.

3. Sexual Dimorphism, in which the sexes vary.

4. Seasonal Dimorphism, in which the successive broods differ.
In order fully to understand the bearing of the following remarks

it is necessary to know something of the anatomy and nomencla-
ture of butterflies. Fig. 3 is an ideal butterfly. The wing margins

A
B.

a.
I.
c.
d.

Fig. 3.

Upper Wing.
Lower Wing.
Costal Margin.
Hind Margin.
Inner „
Anal Angle.
Costa.

fig

Diagram of Butterfly's Wing.

/. Costal nervure.
Sub-costal

g.

h.

j.
k.

do.

Branches of do.
Median nervure.
Sub-median do.
Discoidal Cell.
Discoidal Veins.

Tlie Colouration of Insects. 71

are described as the Costal, which is the upper strong edge of
the wing, the Hind margin, forming the outside, and the Inner
margin, forming the base. The nervures consist of four principal
veins ; the Costal, a simple nervure under the costa, the Sub-costal,
which runs parallel to the costal and about halfway to the tip emits
branches, generally four in number ; the Median occupying the centre
of the wing and sending off branches, usually three in number, and
the Sub-median below which is always simple. There are thus two
simple nervures, one near the costal the other near the inner margin,
and between them are two others which emit branches. Between
these two latter is a wide plain space known as the discoidal cell.
Small veins called the discoidal pass from the hind margin towards the
cell, and little transverse nervures, known as sub- discoidal, often close
the cell. By these nervures the wing is mapped out into a series of
spaces of which one, the discoidal cell, is the most important.

The nervures have two functions, they support and strengthen
the wing, and being hollow serve to convey nutritive fluid and after-
wards air to the wing.

The wings are moved by powerful muscles attached to the base of
the wings close to the body and to the inside of the thorax, all the
muscles being necessarily internal. "There are two sets which
depress the wings ; firstly a double dorsal muscle, running longi-
tudinally upwards in the meso-thorax ; * and, secondly, the dorso-
ventral muscles of the meso and meta-thorax,f which are attached
to the articulations of the wings above, and to the inside of the
thorax beneath. Between these lie the muscles which raise the wings
and which run from the inner side of the back of the thorax to the
legs." t When we consider the immense extent of wing as compared
with the rest of the body, the small area of attachment, and the great
leverage that has to be worked in moving the wings, it is clear that
the area of articulation of the wing to the body is one in which the
most violent movement takes place. It is here that the waste and
repair of tissue must go on with greatest vigour, and we should, on
our theory, expect it to be the seat of strong emphasis. Accordingly
we commonly find it adorned with hairs, and in a vast number of
cases the general hue is darker than that of the rest of the wing,
and so far as we have been able to observe, never lighter than the body

* The middle division of the thorax.

t Hinder division of thorax.

{ Dallas in Cassell's Nat. Hist., vol. vi., p. 27.

72 Colouration in Animals and Plants.

of the wing. Even in the so-called whites (Pieris) this part of the
wing is dusky, and instances are numerous 011 Plate IV.

The scales, which give the colour to the wings, deserve more than
a passing notice. They are inserted by means of little stalks into
corresponding pits in the wing-membrane, and overlap like tiles on a
roof; occasionally the attachment is a ball and socket (Morphines), in
which case it is possible the insect has the power of erecting and
moving its scales. The shapes are very numerous, but as a rule they
are short. To this there is a remarkable exception on the wings of
the males of certain butterflies, consisting of elongated tufted
prominences which appear to be connected with sense-organs. They
are probably scent-glands, and thus we find, even in such minute parts
as scales, a difference of function emphasized by difference of orna-
mentation, here showing itself in variety of forms ; but, as we have
said, ornamentation in form is often closely allied to ornamentation
in colours. In some butterflies, indeed, these scales are aggregated
into spots, as in Danais, and have a different hue from the surround-
ing area.

The scales are not simple structures, but consist of two or more
plates, which are finely striated. The colouring matter consists of
granules, placed in rows between the striae, and may exist upon the
upper surface of the upper membrane (epidermal), or the upper
surface of the under or middle plate (hypodermal), or the colour may
be simple diffraction colour, arising from the interference of the light-
waves by fine striae.

Dr. Haagen, in the admirable paper before mentioned, has
examined this question thoroughly, and gives the results set forth in.
the following table : —

Epidermal Colours.

Metallic blues and greens

Bronze

Gold

Silver
Black
Brown
Red (rarely)

Persistent after death.

The Colouration of Insects.

73

Hypodermal Colours.

Blue
Green
Yellow
Milk-white
Orange and

shades between
Red

Fading after death.

The hypodermal colours are usually lighter than the epidermal,
and are sometimes changed by a voluntary act. Hypodermal and
epidermal colours are, of course, not peculiar to insects ; and, as
regards the former, it is owing to their presence that the changing
hues of fishes, like the sole and plaice, and of the chameleon are due.

The great order Lepidoptera, including butterflies and moths,
seems to the non-scientific mind to be composed of members which
are pretty much alike, the differences being of slight importance ;
but this is not in reality the case, for the lepidoptera might, with some
accuracy, be compared to the mammalia, with its two divisions of the
placental and non-placental animals. Comparing the butterflies
(Rhopalocera) to the placental mammals, we may look upon the
different families as similar to the orders of the mammalia. Were we
as accustomed to notice the differences of butterflies as we are to
remark the various forms of familiar animals, we should no longer con-
sider them as slight, but accord to them their true value. "When in the
mammalia we find animals whose toes differ in number, like the three-
toed rhinoceros and the four-toed tapir, we admit the distinction to be
great, even apart from other outward forms. So, too, the seal and
lion, though both belonging to the carnivora, are readily recognized
as distinct, but the seals may easily be confounded by the casual
observer with the manatees, which belong to quite a different order.

Thus it is with the Lepidoptera, for from six-legged insects, whose
pupae lie buried beneath the soil, like most moths, we pass to the
highest butterflies, whose fore-legs are atrophied, and whose pupae
hang suspended in the open air; and this by easy intermediate
stages. Surely, if six-legged mammals were the rule, we should
look upon four-legged ones as very distinct; and this is the case with
the butterflies. It is necessary to make this clear at starting, in
order that we may appreciate to its full value the changes that have
taken place in the insects under study.

74 Colouration in Animals and Plants.

Butterflies (Rhopalocera) are grouped into four sub-families, as
under : —

1. Nymplialidce, having the fore-legs rudimentary, and the pupae

suspended from the base of the abdomen.

2. Erycinidce, in which the males only have rudimentary fore-

legs.

3. Lyccenida, in which the fore-legs of the males are smaller

than those of the females, and terminate in a simple hook.

4. Papilionidce, which have six perfect pairs of legs, and in which

the pupae assume an upright posture, with a cincture round
the middle.

It may, at first sight, appear curious that the imperfect-legged
NymplialidcB should be placed at the head of the list, but this is based
upon sound reasoning. The larva consists of thirteen segments,
and, in passing to the mature stage, the second segment alone
diminishes in size, and it is to this segment that the first pair of legs
is attached. Looking now to the aerial habits of butterflies, we can
understand how, in the process of evolution towards perfect aerial
structure, the legs, used only for walking, would first become modi-
fied ; and, naturally, those attached to the segment which decreases
with development would be the first affected. When this is found
to be combined with an almost aerial position of the pupae, we see at
once how such insects approach nearest to an ideal flying insect.
It is a general law that suppression of parts takes place as organisms
become specialized. Thus, in the mammalia, the greatest number of
toes and teeth are found in the lowest forms and in the oldest,
simplest fossil species.

A butterfly is, indeed, little more than a beautiful flying machine ;
for the expanse of wing, compared with the size of the body, is
enormous.

CHAPTER XL

THE COLOURATION OF INSECTS.
(Continued?)

General Scheme of Colouring. So various are the patterns dis^
play ed upon the wings of butterflies, that amidst the lines, stripes,
bars, dots, spots, ocelli, scalloppings, etc., it seems at first hopeless to
detect any general underlying principle of decoration ; and this is
the opinion that has been, and is still, held by many who have made
these insects a special study. Nevertheless, we will try to show
that beneath this almost confused complexity lie certain broad
principles, or laws, and that these are expressed J>y the statement
that decoration is primarily dependent upon structure, dependent
upon the laws of emphasis and repetition, and modified by the
necessity for protection or distinction.

To render this subject as plain as possible, British species will be
selected, as far as possible, and foreign ones only used when native
forms do not suffice.

The body of by far the greater number of species is either darker
or of the same tint as the mass of the wings ; and only in rare cases
lighter. When the body has different tints, it is generally found
that the thorax and abdomen differ in colour, and in many cases the
base of the thorax is emphasized by a dark or light band.

On the wings the functional importance of the parts attached to
the body is generally darker, perhaps never lighter, than the ground
of the wing, and is frequently further emphasized by silky hairs.
This has already been sufficiently pointed out.

The wing area may be divided into the strong costal margin, the
hind margin, the nervules, and the spaces; and, however complex
the pattern may be, it is always based upon these structure lines.

M

76 Colouration in Animals and Plants.

In the majority of insects the costal margin is marked with
strong colour. This may be noticed in Papilio Machaon, P. merope,
Vanessa antiopa, and the whites in Plate IV, The extreme tip of the
fore-wings is nearly always marked with colour, though this may
run into the border pattern. This colour is dark or vividly bright,
and we know no butterfly, not even dark ones, that has a light tip to
the wings. Sometimes, it is true, the light bead-border spots run to
the tip, but these are not cases in point. The development of tips
has been traced in Chapter VI, and need not be repeated.

The hind margin of both wings is very commonly emphasized by
a border, of which V. Antiopa, PI. III. Fig. 3, is a very perfect
example.

The border pattern may consist of one or more rows of spots,
lines, bands, or scallops;* and there is frequently a fine fringe,
which in many cases is white, with black marks, and to which the
term bead-pattern may be applied.

A definite relation subsists in most cases between the shape of
the hind margin and the character of the border-pattern. The plain
or simple bordered wings have plain border patterns, and the
scalloped wings have scalloped borders ; or rather scalloped borders
are almost exclusively confined to scalloped wings. In our English
butterflies, for instance, out of the 62 species : —

33 have plain margins to the wings. In all the border is plain,
or wanting.

20 have the fore-wings plain, and the hind wings scalloped,
and in all the hind-wings are scalloped and the fore-
wings plain, or with slightly scalloped border-patterns.
9 have scalloped margins and scalloped border-patterns.

Another relation between structure and pattern is found in those
insects which have tailed hind-wings, for the tail is very frequently
emphasized by a spot, often of a different colour from the rest of the
wing as in the S wallow-Tails, Plates IV. and V.

Yet another point may be noticed. In each wing there is a space,
the discoidal cell, j Fig. 3, at the apex of which several nervures
join, forming knots. These are points at which obstacles exist to the
flow of the contents,and they are almost always marked by a distinct
pattern. We thus have a discoidal spot in very many butterflies, in

* In the true scallop pattern the convexity is turned towards the body of the
insect.

The Colouration of Insects. 77

nearly all moths ; and in the other orders of winged insects the
decoration is even more pronounced, as any one may see who looks
at our dragon-flies, wasps, bees, or even beetles.

In some insects the decoration of the body is very marked, as in our
small dragon-flies, the Agrions. In one species, for example, A. Puella,
the male is pale blue banded with black, and the female bronze
black, with a blue band on the segment, bearing the sexual organ ;
the ovipositors are also separately decorated, The male generative
organs are peculiar, in that the fertilizing fluid is conveyed from one
segment to a reservoir at the other end of the abdomen. Both the
segments bearing these organs are marked by special decoration.
The peculiar arrangement of the sexual organs in dragon-flies is very
variable, and certain segments are modified or suppressed in some
forms, as was shown by J. W. Fuller.* In every case the decoration
follows the modification. In the thorax of dragon-flies, too, the
principal muscular bands are marked out in black lines. This
distinct representation of the internal structure is beautifully shown
in ^Eschna and Gomphina, and in the thorax of Cicada, as shown
by Dr. Haagen in the paper quoted in the last chapter.

We may, then, safely pronounce that the decoration of insects is
eminently structural.

Simple Variation. Cases of simple variation have been already
cited in our description of spots and stripes, and it only remains to
show that in this, as in all other cases, the variation is due to a
modification of original structural decoration.

To take familiar examples. Newman, in his British Butterflies,
figures the varieties of the very common Small Tortoiseshell ( Vanessa
urticcB). In the normal form there is a conspicuous white spot on
the disc of the fore-wings, which is absent in the first variety, owing
to the spreading of the red-brown ground colour. This variety is
permanent on the Mediterranean shores. In variety two, the second
black band, running from the costa across the cell, is continued
across the wing. The third variety, Mr. Newman remarks, is
" altogether abnormal, the form and colouring being entirely altered."
Still, when we examine the insect closely, we find it is only a modi-
fication of the original form. The first striking difference is in the
margin ot the wings, which in the normal form is scalloped with
scallop-markings, whereas, in the variety the margins are much
simpler, and the border pattern closely corresponds with it, having

* J. W. Fuller on the Breathing Apparatus of Aquatic Larvae. Proc. Bristol

Nat. Soc.

78 Colouration in Animals and Plants.

lost its scalloping. In the fore-wing gome of the black bands and
spots are suppressed or extended, and the extensions end rigidly
at nervules. The dark colouring of the hind-wings has spread over
the whole wing. We thus see that the decoration, even in varieties
called abnormal, still holds to structural lines, and is a development
of pre-existing patterns.

No one can have examined large series of any species without
being impressed with the modification of patterns in almost every
possible way. For instance, we have reared quantities of Papilio
Machaon, and find great differences, not only in the pattern, but in
the colour itself. A number of pupae from Wicken Fen, Cambridge-
shire, were placed in cages, into which only coloured light could
fall, and though these experiments are not sufficiently extended to
allow us to form any sound conclusions as to the effect of the
coloured light, we got more varieties than could be expected from
a batch of pupae from the same locality. The tone of the yellow,
the quantity of red, the proportion of the yellow to the blue scales
in the clouds, varied considerably, but always along the known and
established lines.

The variations in the colour of Lepidoptera has been most
admirably treated by Mr. J. Jenner Weir in a paper, only too short,
read before the West Kent Natural History Society.* He divides
variations into two sections, Aberrations or Heteromorphism, and
constant variations or Orthopaicilism, and subdivides each into six
classes, as under : —
Heteromorphism.

Albinism ... ... white varieties.

Melanism black do.

Xanthism ... ... pallid do.

Sports ... ... or occasional variations not in-

cluded in the above.

Gynandrochomism ... females coloured as males.

Hermaphroditism ... sexes united.
Orthoptccitism.

Polymorphism ... variable species.

Topomorphism ... local varieties.

Atavism ... ... reversion to older forms.

Dimorphism two constant forms.

Trimorphism three do. do.

Horeomorphism ... seasonal variation.
* Entomologist, vol. xvi., p. 1G9, 1883.

The Colouration of Insects. 79

In some cases, he remarks, variations are met with which may
with equal propriety be classed in either section.

Albinism he finds to be very rare in British species, the only
locality known to him being the Outer Hebrides. This reminds us
of Wallace's remark upon the tendency to albinism in islands.
Xanthism, he finds to be more plentiful, and quotes the common
Small Heath (Canonympha pamphilus) as an illustration. In these
varieties we have simply a bleaching of the colouring matter of the
wings, and therefore no departure from structural lines. Melanism
arises from the spreading of large black spots or bars, or, as in
Biston betularia, a white moth peppered with black, dots by the
confluence of small spots ; for this insect in the north is sometimes
entirely black. It is singular that insects have a tendency to
become melanic in northern and alpine places, and this is especially
the case with white or light coloured species. (See Plate IV. Fig. 17)
It has recently been suggested that this darkening of these delicate
membranous beings in cold regions is for the purpose of absorbing
heat, and this seems very probable.*

Of ordinary spots it is merely necessary to remark, that they
are all cases in our favour. Thus, in Satyrus hyperanthus we have
" the ordinary round spots . . . changed into lanceolate markings " ;
this takes place also in C. davus. The other cases of aberration do
not concern us.

When, however, we come to the cases in which a species has
two or more permanent forms, it is necessary to show that they are
in all cases founded on structure lines. The patterns, as shown in
Plate V., Figs. 1-13, are always arranged structurally, and the
fact that not only are intermediate forms known, as in Araschnia
porima, Plate V., Fig. 6, but that the various forms are con-
vertible into one another, would in itself be sufficient to show that
in these cases there is no departure from the general law. In
Grapta interrogations, Plate V., Figs. 8-10, we see in the central
figure one large spot above the median nervure, in the left-hand
form this is surmounted by another spot above the lowest sub-costal
branch, and in the right-hand figure this latter spot is very
indistinct. We have here a perfect gradation, and the same may
be said of the colouration of the lower wings. Take again the
three forms of Papilio Ajax in the same plate, Figs. 11-13, and we
have again only modifications of the same type.

* Nature. E. Meldola on Melanism, 1885.

80 Colouration in Animals and Plants.

In local varieties, as in seasonal forms, we have again nothing
more than developments of a given type, as is well shown in Plates
IV. & V., Figs. 13-18 & 1-13.

When, however, we come to mimetic forms, whether they mimic
plants, as in Plate I., or other species, as in Plates II. & III., a
difficulty does seem to arise.

The leaf butterfly (Kallima inachus), Plate I., offers no trouble
when we view the upper surface only with its orange bands, but its
under surface, so marvellously like a dead leaf that even holes and
microscopic fungi are suggested, does seem very like a case
in which structure lines are ignored. Take, for instance, the mark
which corresponds to the mid-ribs, running from the tail to the apex
of the upper wing ; it does not correspond to any structure line of
the insect. But if we take allied and even very different species
and genera of Indian and Malayan butterflies, we shall find every
possible intermediate form between this perfect mimicry and a total
lack of such characters. To cite the most recent authority, the
various species of the Genera Discophora, Amathusia, Zeuxidia,
Thaumantis, Precis, &c., figured so accurately in Distant's Rhopa-
locera Malayana, will give all the steps.

In the cases of true mimicry, as in Figs. 1-3, Plates II. & III.,
where insects as different as sheep from cats copy one another, we
find that of course structure lines are followed, though the pattern
is vastly changed. The Papilio merope, Fig. 1, Plate II., which
mimics Danais niavius, Fig. 3, does so by suppressing the tail
appendage, changing the creamy yellow to white — a very easy
change, constantly seen in our own Pieridse — and diffusing the
black. A similar case is seen in Figs. 4-5, Plate III., where a
normally white butterfly (Panopoea hirta) mimics a normally dark
one of quite a different section. Here again the change is not
beyond our power of explanation. Where a Papilio like merope
mimics a brown species like Danais niavius, we have a still greater
change in colour, but not in structural pattern.

If we ascribe to these insects the small dose of intelligence we
believe them to possess, we can readily see how the sense of need
has developed such forms.

Local varieties present no difficulty under such explanation.
The paramount necessity for protection has given the Hebridran
species the grey colour of the rocks, and the desert species their
sandy hue.

To face page 80.]

Plate VIT.

The Colouration of Insects. 81

Finally, to take the case of caterpillars, Weismann has admirably
worked out the life history of many forms, and shows how the
complex markings have arisen by development. Broadly, a cater-
pillar consists of 13 segments, the head being one. The head is
often marked with darker colour, and the last segment with its
clasping feet is also very frequently emphasized, as in Figs. 1 & 3,
Plate VII. The spiracles are generally marked by a series of spots,
and often connected by a line. Here the tendency to repetition
shows itself strongly, for not only the spiracles themselves, but the
corresponding points in the segments without spiracles are frequently
spotted, and, moreover, these spots are frequently repeated in rows
above the spiracular line. Of this, Deilephila galii and D. JEuphorbice,
Figs. 1-5, Plate VII., are good examples.

The segmentation is also generally emphasized, as shown in all
the examples on the plate, but in its simplicity in Fig. 10.

Running down the centre of the back a more or less distinct
line is often seen, as shown in the figures. This corresponds with
the great dorsal alimentary canal lying just below the skin, and
Weismann has shown that in young larvae this line is transparent,
and the green food can be seen through the skin. We have here,
perhaps, a relic of the direct colouration noticed in the transparent
coelenterata.

Where larvae possess horns either upon the head, as in Apatura
iris and Papilio machaon, or on the tail, as in many of the sphyngidae,
like Figs. 1-5, Plate VII., these appendages are always emphasized
in colour. As they are frequently oblique, we often find that this
obliquity is continued as a slanting spot, as in D. galii and enphorbice,
and sometimes repeated as a series of oblique stripes, as in Fig. 4.

It must be admitted that in insects we have strong evidence of
structural decoration.

CHAPTER XII.

ARACHNIDA.

THE Araclinida include the scorpions and spiders, and as the
former are tolerably uniform in colour, our remarks will be
confined to the latter.

The thorax is covered with a horny plate, while the abdomen
only possesses a soft skin, and neither show any traces of segmenta-
tion. From the thorax spring four pairs of legs, and a pair of
palpi, or feelers. Immediately beneath the skin of the abdomen
lies the great dorsal vessel, which serves as a heart. This vessel
is divided into three chambers, the general aspect of which is
shown in Fig. 9, Plate VIII., taken from Gegenbaur's Comparative
Anatomy.*

From this heart the blood passes by vessels to each of the limbs,
the palpi, etc., as offsets from the double-branched aorta. The shape
of this dorsal vessel is peculiar, and its importance in respect to
colouration will be immediately apparent.

The primary scheme of colouration in the Arachnida seems to be
the distinguishing of the cephalothorax from the abdomen by a
different colour. Thus, of the 272 species of British spiders repre-
sented in Blackwell's work,f no less than 203 have these parts
differently coloured, and only 69 are of the same hue, and even in
these there is often a difference of tint. So marked is this in certain
cases that the two parts form vivid contrasts. Of this cases are
given in the following list.

Cephalothorax. Abdomen.

Eresus cinnabarinus, Black, Bright Red.

Thomisus floricolens, Green, Brown.

cinereus, Brown, Blue.

trux, Red, Brown.

Sparassus smaragdulus, Green, Red and yellow.

* Elements of Comparative Anatomy, by C. Gegenbaur. Translated by Jeffrey
Bell and Kay Lankester, 1878, p. 285.

t Spiders of Great Britain and Ireland, J. Blackwell. Eay. Soc., 1861.

Araclmida. 83

As a rule the abdomen is darker than the cephalothorax, and
many species have the former red-brown and the latter black.

The legs, usually, take the colour of the cephalothorax, and are,
hence, generally lighter than the abdomen, but to this there are
exceptions. Where the individual legs differ in colour, the two first
pairs are the darkest, and the dark hue corresponds in tint with the
dark markings on the cephalothorax. The joints of the legs are in
many species emphasized with dark colour, which is often repeated
in bands along the limb.

The most remarkable point is, however, the pattern on the
abdomen, which, though varied in all possible ways, always
preserves a general character, so that we might speak with pro-
priety of a spider-back pattern. This pattern is fairly well
illustrated in the genus Lycosa, but is seen to perfection, and in its
simplest form in Segestria senoculata, Plate VIII., Fig. 1, and in
Sparassus smaragdulus, Plate VIII., Fig. 2.

This peculiar pattern is so like the dorsal-vessel that lies just
beneath, that it is difficult to avoid the conclusion that we have here
an actual case of the influence of internal organs on the integument,
and this we believe to be the case. No matter how curious the
abdominal markings may seem to be, they never so far depart from
this fundamental pattern as to appear independent of it.

Thus, in the genus Lycosa, which is by no means the best for the
purpose, but is chosen as illustrating Gegenbaur's diagram, PI. VIII.,
we have the dorsal-vessel well marked in L. piscatoria, Plate VIII., Fig.
3, from which may be developed the other forms. In L. andrenivora
Plate VIII., Fig. 4, the male shows the vessel-mark attenuated pos-
teriorly; and in the female, Fig. 5, the hinder part has become
broken up into detached marks, still preserving the original shape,
while the upper part remains practically unchanged. In L. allodroma
the disintegration of the mark has further advanced, for in the male,
Fig. 6, the upper portion has lost something of its shape, and the
lower part is a series of isolated segments. This process is carried
still further in the female, Fig. 8, where the upper portion is
simplified, and the lower almost gone. In L. campestris, Fig. 10, the
mark is reduced to a stripe, corresponding with the upper part of the
vessel-mark only : and, lastly, in the male L. agretyca, Fig. 7, this
upper part is represented by two spots, though even here traces of
the original form can be seen.

A simplification of marking of another sort is seen in L. rapax,

N

84 Colouration in Animals and Plants.

Fig. 13, where the chamber-markings are almost obliterated, and
merely an irregular stripe left. The stages by which this modifi-
cation is arrived at are too obvious to need illustration.

In some species the lower portion of the vessel-mark is reduced
to small dots, as in L. cambrica, flumatilis, piratica, and others ; and
the stages are very clear. Starting with the isolated chamber-
marks, as in L. allodroma, Fig. 5, we get, firstly, a set of spots, as in
L. picta, which, in the female, Fig. 16, are still connected with the
chamber-marks, but in the male, Fig. 17, are isolated. This leads
us, by easy steps, to such forms as L. latitans, Fig. 14, which consists
of a double row of spots upon dark stripes.

The intimate connection thus shown to subsist between the
characteristic decoration of the abdomen of spiders, and the shape of
the important dorsal organ beneath, seems to be strong evidence of
eifect that internal structure may have upon external decoration.*

The cephalothorax of spiders, being covered with a hardened
membrane, does not show such evidence clearly, for it appears to be a
law that the harder the covering tissue, the less does it reflect, as it
were, the internal organs. The hard plates of the armadillo are
thus in strong contrast to the softer skins of other animals.

Nevertheless, there does appear, occasionally, to be some trace of
this kind of decoration in the cephalothorax of certain spiders,
though it would be hard to prove. The blood vessels of this part
(see Fig. 9). though large, are not nearly so prominent as the great
dorsal vessel. The chief artery enters the cephalothorax as a
straight tube, forks, and sends branches to the limbs, palpi, and eyes.
In many species, notably in the genus Thomisus, a furcate mark
seems to shadow the forked aorta. This is best shown in T. luctuosus,
Plate VIII., Fig. 11. Moreover, in this and other genera, lines
frequently run to the outer pair of eyes, which alone are supplied
with large arteries, see Fig. 9.

However this may be, it is certain that the entire decoration of
spiders follows structural lines, and that the great dorsal vessel has
been emphasized by the peculiar pattern of the abdomen.

* The decoration of many of the Hoverer flies and wasps is of a similar character.

o fii<\ /<"</< M. |

Plate VIJI.

*

SPIDERS.

CHAPTER XIII.

COLOURATION OF INVERTEBRATA (Continued).

OF the Arthropoda, including the lobsters, crabs, shrimps, etc.,
little can be said here, as we have not yet been able to study
them with anything like completeness. Still, we find the same laws
to hold good. The animals are segmented, and we find their system
of colouration segmental also. Thus, in the lobsters and crabs there
is no dorsal line, but the segments are separately and definitely
decorated. The various organs, such as the antennae and eyes, are
picked out in colour, as may be beautifully seen in some prawns.

When we come to the Mollusca, we meet with two distinct types,
so far as our subject is concerned ; the naked and the shelled. In
the naked molluscs, like the slugs, we have decoration applied region-
ally, as is shown to perfection in the Nudibranchs, whose feathery
gills are often the seat of some of the most vivid hues in nature.

The shell-bearing mollusca are proverbial for their beauty, but it
is essential to bear in mind that the shell does not bear the same
relation to the mollusc that the " shell " of a lobster does to that
animal. The lobster's shell is part of its living body ; it is a true
exo-skeleton, whereas the shell of a mollusc is a more extraneous
structure — a house built by the creature. We ought, on our view,
to find no more relation between the decoration of a shell and the
structure of its occupant, than we do in the decoration of a human
dwelling-house to the tenant.

The shell consists of carbonate of lime, under one or both of the
forms known to mineralogists as calcite and aragonite. This
mineral matter is secreted by an organ called the mantle, and the
edge, or lip, of the mantle is the part applied to this purpose. The
edge of the mantle is the builder's hand, which lays the calcareous

86 Colouration in Animals aad Plants.

stones of the edifice. The shell is built up from the edge, and the
action is not continuous but seasonal, hence arise the markings
known as lines of growth. In some cases the mantle is expanded
at times into wing-like processes, which are turned back over the
shell, and deposit additional layers, thus thickening the shell.

In all the forms of life hitherto considered the colouring matter
is deposited, or formed, in the substance of the organ, or epidermal
covering, but in the niollusca this is not the case. The colouring
matter is entirely upon the surface, and is, as it were, stencilled on to
the colourless shell. This is precisely analogous to the colouring of
the shells of birds' eggs. They, too, are calcareous envelopes, and
the colouring matter is applied to the outside, as anyone can see by
rubbing a coloured egg. In some eggs several layers of colouring
matter are superimposed.

In no case does the external decoration of molluscan shells follow
the structure lines of the animal, but it does follow the shape of the
mantle. The secreting edge may be smooth, as in Mactra, regularly
puckered, as in most Pectens, puckered at certain points, as in
Trigonia, or thrown into long folds, as in Spondylus. In each of
these cases the shell naturally takes' the form of the mantle. It is
smooth in Mactra, regularly ribbed in Pecten, tubercled in Trigonia,
and spined in Spondylus. Where the inside of the shell is coloured
as in some Pectens, regional decoration at once appears and the
paleal lines, and muscular impressions are bounded or mapped out
with colour.

It is a significant fact that smooth bivalves are not so ornate as
rugose ones, and that the ridges, spines, and tubercles of the latter
are the seats of the most prominent colour.

Similar remarks apply to univalve shells, which are wound on an
imaginary vertical axis. They may be smooth, as in Conus and Oliva,
rugose, as in Cerithium, or spined, as in Murex. The structure of
these shells being more complex than that of bivalves, we find, as a
rule, they are more lavishly ornamented, and the prominent parts of
the shell, and especially the borders, are the seat of strongest colour.
In some cases, as in adult Cowries (Cyprtea), the mantle is reflexed
BO as to meet along the median line, where we see the darkest
colour.

The rule amongst spiral shells is to possess spiral arid marginal
decoration, and this is what we should expect. The Nautilus repeats
in the red-brown markings of its shell, the shape of the septa which

Colouration of Invertebrata. 87

divide the chambers, though, as is often the case, they are generally
more numerous than the septa.

The naked Cephalopoda, or cuttle-fishes, often possess a distinct
dorsal stripe, and when our views were first brought before the
Zoological Society, this fact was cited as an objection. To us it
seems one of the strongest of favourable cases, for these animals
possess a sort of backbone — the well-known cuttle-bone — and hence
they have a dorsal line.

Some shells, as Margarita catenata, have a chain-pattern, and in
this case the action of the pigment cells takes place at regular and
short intervals. Others, as Mactra stultorum, the stencilling forms a
series of lines and spots, generally enlarging into rays.

The whole subject of the decoration of shells deserves much
more time than we have been able to give to it as yet.

CHAPTER XIV.

COLOURATION OF VERTEBRATA.

THE vertebrata, as their name implies, are distinguished by the
possession of an internal skeleton, of which the backbone is the
most essential part, and the general, but not universal, possession of
limbs or appendages.

Consequently we find that the dorsal and ventral surfaces are
almost invariably coloured differently, and the dorsal is the darker
in the great majority of instances. Generally the spine is marked
by a more or less defined central line, and hence this system of
colouration may be termed axial, because it is in the direction of the
axes, or applied about the axes.

Fishes. Where fishes have not been modified out of their original
form, as are the soles, plaice, and other flat fish, we find the dorsal
region darker than the ventral, and even here the under surfaces are
the lightest. Even in cases like the Char, Fig. 1, Plate IX., where
vivid colour is applied to the abdomen, the dorsum is the darker.
The dorsum is often marked by a more or less well-defined dark
band, as in the mackerel and perch, Fig. 2, Plate IX. There are
sometimes parallel bands at right angles to the above, as in the
perch and mackerel ; and this is a common feature, and apparently
a very old one, as we find it in the young of fishes whose adults are
without these rib-like marks, such as the trout and pike.

It is only necessary to inspect any drawings of fishes to see that
their colouration is on a definite principle, although rather erratic.
Important functional parts, like the gills, fins, and tail, are generally
marked in colour more or less distinctly, as may be seen, for instance,
in our common fresh-water fishes, like the roach and perch. The
line of mucus-secreting glands running along the sides is usually

Colouration of Vertebrata. 89

marked by a dark line. These facts point distinctly to structural
decoration.

There are in some fishes, like the John Dory, curious eye-like
dark spots, which we cannot refer to a structural origin, though a
better acquaintance with the class might reveal such significance.

The Amphibia have not been well studied by us, and we must
leave them with the remark that they seem to bear out the view of
structural decoration, as is seen in our English newts. Some are,
however, modified out of all easy recognition.

Reptiles. Among the reptiles, the snakes, Fig. 4, may be selected
for illustration. Snakes are practically little more than elongated
backbones, and are peculiar from the absence of limbs. The colour-
ing matter does not reside so much in the scales as in the skin
beneath, so that the sloughs do not illustrate the decoration.
Hence, we might expect to find here a direct effect of morphological
emphasis.

The ornamentation of snakes is very similar throughout the class,
both in water and land snakes ; as may be seen by Sir W. Fayrer's
work on Venomous Snakes. This ornamentation is of a vertebral
pattern, placed along the dorsal surface, with cross lines, which may
represent ribs.

Where the ribs are wanting, as in the neck, the pattern changes,
and we get merely longitudinal markings.

In the Python, Fig. 4, there are, near the central line, numerous
round spots, which apparently emphasize the neural processes.
There are diagonal markings on some species which illustrate the
development of colour-spots already alluded to.

This snake-pattern is very singular and striking. The markings
are fewer in number than the vertebrae, yet their true vertebral
character is most obvious.

In Snakes, again, we find the dorsal region is darker than the
ventral.

In the Lizards there are patches of colour placed axially, while
each patch covers a number of scales.

Birds. Birds have their whole economy modified to subserve
their great functional peculiarity of flight.

Immense muscles are required for the downward stroke of the
wing, and to give attachment to these the sterum has a strongly
developed keel. To bring the centre of gravity low, even the
muscles which raise the wing are attached to the sternum, or breast-

90 Colouration in Animals and Plants.

bone, instead of to the dorsal region, as might be expected ; and to
brace the wings back a strong furculum — the merry-thought — is
attached. The breast, then, is the seat of the greatest functional
activity in birds, and, consequently, we find in a vast number of
birds that the breast is the seat of vivid colour.

As many birds are modified for protective purposes, the brightest
species were selected to test our views, namely, the Birds of
Paradise (Paradisea), Humming Birds (Trochilidas), and Sun Birds
(Nectarinidae). In these birds it is clear that colour has had full
sway, untramelled by any necessity for modification.

Nothing is more striking than the mapping out of the surface of
these birds into regions of colour, and these regions are always
bounded by structural lines.

Take, for instance, Paradisea regia. In this bird we find the
following regions mapped in colour: —

Sternum ... ... brown.

Clavicle ... ... yellow.

Pelvis ... ... yellow.

Band ... ... brown.

Frontal bone ... ... black.

Parutal bones ... ... green.

Occiput ... ... yellow.

A beautiful ruff emphasizes the pectoral muscles, and the tail
appendages emphasize the share-like caudal vertebrae.

If we turn to the other species of this genus, we find in P. Papuana
the claret breast suddenly change to green at the furculum ; and
similar changes take place in P. speciosa, while in P. Wallacei and
Wilsoni this region is decorated with a wonderful apron of metallic
green.

The region of the furculum is equally well marked in the Toucans
and Sun-birds.

If now we observe the back of a bird, and view the skeleton with
the wings at rest, we shall find it falls into three morphological
tracts. First, the shoulder, or scapular track ; second, the thigh, or
pelvic ; third, the tail, or caudal region ; and in all these birds the
several tracts are beautifully marked by sudden and contrasted
change of colour. In P. Wilsoni all the tracts are brilliant red, but
they are separated by jet-black borders. In Nectarinea chloropygia
the scapular region is red, the pelvic yellow, and the caudal green.

To face page 90.]

iofre in

Plate X.

SUN BIRDS,

Colouration of Vertebrata. 91

In P. Wilsoni we have a wonderful example of morphological
emphasis. The head is bare of feathers, and coloured blue, except
along the sutures of the skull, where lines of tiny black feathers
map out the various bones.

But morphological emphasis exists everywhere in birds. The
wing-primaries, which attach to the hand, are frequently differently
decorated from the secondaries, which feathers spring from the ulna ;
and the spur-feathers of the thumb, or pollux, are different in shape,
and often in colour, from the others, as every fly-fisher who has used
woodcock spur-feathers knows full well. The wing-coverts and tail-
coverts are frequently mapped in colour; and the brain case is
marked by coloured crests. The eye and ear are marked by lines
and stripes ; and so we might go on throughout the whole bird. We
may remark that these very tracts are most valuable for the
description and detection of species, and among ornithologists
receive special names.

Now, this distribution of colour is the more remarkable inasmuch
as the feathers which cover the surface — the contour feathers — are
not evenly distributed over the body, but are confined to certain
limited tracts, as shown by Nitzsch ; and though these tracts have a
morphological origin, they are rendered quite subsidiary to the
colouration, which affects the whole bird, and not these regions in
particular. In fact, the colouration is dependent upon the regions
on which the feathers lie, and not upon the area from which they
spring. In other words, we seem to have in birds evidence of the
direct action of underlying parts upon the surface.

In more obscurely coloured birds, and those which seem to be
evenly spotted, close examination shows that even here the decora-
tion is not uniform, but the sizes and axes of the spots change
slightly as they occupy different regions ; as may be seen in Wood-
peckers and Guinea-fowl.

Although the same tone of colour may prevail throughout the
plumage, as in the Argus Pheasant, great variety is obtained by the
fusion of spots into stripes. A symmetrical effect is produced by the
grouping of unsymmetrical feathers ; as is so often seen in plants,
where irregular branches and leaves produce a regular contour.

Sometimes, especially on the breast and back, the feathers of one
region seem to unite so as to form one tract, so far as colour is
concerned. Thus, if in P. Wilsoni the black borders of the dorsal
regions were suppressed, all three areas would be of one hue. This

O

92 Colouration in Animals and Plants.

seems to have been the case in the breast region of Humming Birds,
where only the throat is highly coloured. In the Toucans the breast
and throat regions are often marked with colour ; but sometimes the
hue is the same and the boundaries of the regions marked with a
band of another colour; if this boundary band be increased, the
regions do not seem so well shown, for the boundary becomes as
broad as the area ; yet, in all these cases the dependence upon
regional decoration is manifest. No doubt the few uniformly
coloured birds were derived from species which were once variously
hued ; the gradation of colour being lost in transmission.

Mammalia. The axial decoration of the mammalia is very
definite, and nearly all species have a dorsal tract marked with
colour. The dark bands on the back of the horse, ox, and ass, are
cases in point. In nearly every case the dorsal is darker than the
ventral surface.

If we take highly decorated species, that is, animals marked by
alternate dark and light bands, or spots, such as the zebra, some
deer, or the carnivora, we find, first, that the region of the spinal
column is marked by a dark stripe (Figs. 9 & 16) ; secondly, that
the regions of the appendages, or limbs, are differently marked;
thirdly, that the flanks are striped, or spotted, along or between the
regions of the lines of the ribs ; fourthly, that the shoulder and hip
regions are marked by curved lines ; fifthly, that the pattern
changes, and the direction of the lines, or spots, at the head, neck,
and every joint of the limbs ; and lastly, that the tips of the ears,
nose, tail, and feet, and the eye are emphasized in colour. In
spotted animals the greatest length of the spot is generally in the
direction of the largest development of the skeleton.

This morphological arrangement can be traced even when the
decoration has been modified. Thus, in the carnivora we have the
lion and puma, which live in open country, with plain skins, the
tiger with stripes, an inhabitant of the jungle, and the leopard,
ocelot, and jaguar with spots, inhabiting the forests.

But the lion has a dark dorsal stripe, and the nose, etc., are
emphasized in colour, and, moreover, the lion has probably lost its
marked decoration for protective purposes, for young lions are
spotted. The tiger's stripes start from the vertebras, and still
follow the lines of the ribs. In the tiger the decoration changes at
the neck, and on the head, and the cervical vertebrae are often
indicated by seven stripes. See Fig. 5.

Colouration of Vertebrata. 93

The markings over the vertebrae are not in continuous lines, as
in many mammals, but form a series of vertebra-like spots. This
plan of decoration is continued even on the tail, which is coloured
more on the upper than on the lower surface.

The spotted cats have their spot-groups arranged on the flanks
in the direction of the ribs, at the shoulder and haunch in curves, at
the neck in another pattern, on the back of the head in another; and
the pattern changes as each limb-joint is reached, the spots decreas-
ing in size as the distance is greater from the spine. See Figs. 9-15.

There is in tigers, and the cat-tribe generally, a dark stripe over
the dental nerve ; and the zygoma, or cheek-bone, is often marked
by colour. Even the supraorbital nerve is shown in the forehead,
and there are dark rings round the ears. In dissecting an ocelot at
the Zoological Gardens in 1883, a forked line was found immediately
over the fork of the jugular vein.

The colouration in these animals seems often to be determined
by the great nerves and nerve-centres, and the change from spots,
or stripes, to wrinkled lines on the head are strikingly suggestive
of the convolutions of the brain, falling, as they do, into two lateral
masses, corresponding with the cerebral hemispheres, separated by a
straight line, corresponding with the median fissure. This is well
shown in the ocelot, Fig. 15, and in many other cats.

That the nerves can affect the skin has already been pointed out
in Chapter VI., in the case of herpes, and that it can affect colour is
shown in the Hindoo described in the same place.

So marked, indeed, is this emphasis of sensitive parts that every
hair of the movable feelers of a cat is shown by colour to be
different in function from the hairs of the neck, or from the stationary
mass of hair from which the single longer hair starts.

In the Badger, Fig. 16, there is a bulge-shaped mass of coloured
hair near the dorsal and lumbar regions, but it is axially placed.
The shoulder and loins are well marked, although in a different
manner from other species. In some species of deer, and other
mammalia, there are white or coloured lines parallel to the spine,
and also, as in birds, spots coalesce and form lines, and lines break
up into spots.

The great anteater has what at first seems an exceptional mark-
ing on the shoulder, but a careful examination of the fine specimen
which died at the Zoological Gardens in 1883, we were struck with
the abnormal character of the scapula, and we must remember that,

94 Colouration in Animals and Plants.

as Wallace and Darwin have pointed out, all abnormal changes of
the teeth are correlated with changes in the hair. Moreover the
muscles of the shoulder region are so enormously developed as to
render this otherwise defenceless animal so formidable that even the
jaguar avoids an embrace which tightens to a death-grip. This region
is, therefore, precisely the one we should expect to be strongly
emphasized. This being the case, we have really no exception in
this creature.

Certain mammals are banded horizontally along their sides, thus
losing most of their axial decoration, and this is well shown among
the Viverridae, and smaller rodents. Now, however conspicuous
such animals may appear in collections, they are in their native
haunts very difficult to detect. In all cases there is a marked dorsal
line ; and we suggest that the mature decoration is due to a suppres-
sion of the axial decoration for protective purposes, and a repetition
of the dorsal decoration according to the law before enunciated.
Indeed, in one case we were able to trace this pretty clearly, in the
beautiful series of Sus vittatus in the museum at Leyden. This pig,
an inhabitant of Java, when mature is a dark brown animal, but in
the very young state it is clearly marked in yellow and brown, with
a dark dorsal stripe, and spots, taking the line of the ribs, and over
the shoulder and thigh. As the animal grows older, the spots run
into stripes, and it becomes as clearly banded horizontally as the
viverridse. Finally the dark bands increase in width, until they
unite, and the creature becomes almost uniformly brown.

We have not been able to see young specimens of the viverridse,
but a similar change may there occur, or it may have occurred in
former times. We must also remember that these creatures are
long-bodied, like the weasels, and hence they may have a tendency
to produce long stripes.

In the case of our domestic animals, especially the oxen, the
decoration seems often to have become irregular, but even here the
emphasis of the extremities is generally clearly made out, and that
of the limbs can often be traced. In horses this is better shown, and
dappled varieties often well illustrate the points. Most horses at
some time show traces of spots.

Sufficient has now been said to point out the laws we believe to
have regulated the decoration of the animal kingdom. The full
working out of the question must be left to the future, but it is
hoped that a solid groundwork has been laid down.

'1 o face fiaye <J5.]

Plate XI.

LEAVES.

R £ Skrr/c/r/* del. ad nat

CHAPTER XV.

THE COLOURATION OF PLANTS.

general structure of plants is so simple in comparison with
J_ that of animals that our remarks upon this sub-kingdom need
only be short.

With regard to leaves, especially such as are brightly coloured,
like the Begonias, Caladimus, Coleus, and Anoechtochilus, Plate XI.,
the colour follows pretty closely the lines of structure. We have
border decoration, marking out the vein-pattern of the border ; the
veins are frequently the seat of vivid colour, and when decolour-
ation takes place, as in variegated plants, we find it running along
the interspaces of the veins. These facts are too patent to need
much illustration ; for our zonale geraniums, ribbon grasses, and
beautiful-leaved plants generally, are now so common that everyone
knows their character. When decay sets in, and oxidation gives
rise to the vivid hues of autumn, we find the tints taking structural
lines, as is well shown in dying vine and horse-chestnut leaves, Fig.
1, Plate XI. This shows us that there is a structural possibility of
acquiring regional colouration.

We must remember, too, that the negative colouration of these
dying leaves is of very much the same character as the positive
colouration of flowers, for flowers are modified leaves, and their hues
are due to the oxidation of the valuable chlorophyll.

In leaves the tendency of spots to elongate in the direction of the
leaf is very marked, as may be well seen in Begonia. Fig. 17,
drawn to illustrate another point, shows this partly. When leaves
are unsymmetrical, like the begonias, the pattern is unsymmetrical
also.

Among parallel veined leaves we find parallel decoration. Thus,

96 Colouration in Animals and Plants.

in the Calatheas we have dark marks running along the veins. In
Draccena ferrea we have a dark green leaf, with a red border and tip,
the red running downwards along the veins. This action may be
continued until the leaf is all red except the mid-rib, which remains
green. In long net-veined leaves we may cite Pavetta Borbonica,
whose dark green blade has a crimson mid-rib. Of unsymmetrical
leaves those in the plate may suffice.

When we come to flowers, the same general law prevails, and is
generally more marked in wild than in cultivated forms, which have
been much, and to some extent unnaturally, modified. Broadly
speaking, when a flower is regular the decoration is alike on all the
parts ; the petals are alike in size, the decoration is similar in each, but
where they differ in size the decoration changes. Thus, in Pelar-
goniums we may find all five petals alike, or the two upper petals
may be longer or shorter than the lower three. In the first case
each is coloured similarly, in the other the colour pattern varies with
the size of the petal. The same may be seen in Rhododendron.

Where the petals are united the same law holds good. In
regular flowers, like the lilies, the colouration is equal. In irregular
flowers, like the snapdragon and foxglove, the decoration is irregular.
In Gloxinia the petals may be either regular or irregular, and the
decoration changes in concert.

A very instructive case was noticed by one of us in Lamium
galeobdolon, or yellow Archangel. This plant is normally a labiate
with the usual irregular corolla, but we have found it regular, and in
this instance the normal irregular decoration was changed to a
regular pattern on each petal.

In gamopetalous flowers the line of junction of the petals is
frequently marked with colour, and we know of no case in which a
pattern runs deliberately across this structure line, though a blotch
may spread from it.

When we remember that flowers are absolutely the result of the
efforts of plants to secure the fertilizing attention of insects, and
that they are supreme efforts, put forth at the expense of a great
deal of vegetable energy — that they are sacrifices to the necessity
for offspring — it does strike us forcibly when we see that even under
these circumstances the great law of structural decoration has to be
adhered to.

To face page 96.]

Plate

Plate XII.

_ •

FLOWERS;

CHAPTER XVI.

CONCLUSIONS.

WE have now, more or less fully, examined into the system of
colouration in the living world, and have drawn certain
inferences from the facts observed.

It appears that colouration began — perhaps as a product of
digestion — by the application of pigment to the organs of trans-
parent creatures. Supposing that evolution be true — and, if we may
not accept this theory there is no use in induction whatever — it
must follow that even the highest animals have in the past been
transparent objects. This was admirably illustrated by Prof. Ray
Lankester in a lecture on the development of the eyes of certain
animals, before the British Association meeting at Sheffield, in which
it was shown that the eyes commenced below the surface, and were
useful even then, for its " body was full of light."

Granting this, it follows that the fundamental law of decoration
is a structural one. Assuming, as we do, that memory has played a
most important part in evolution, it follows that all living matter
has a profound experience in decorating its organs — it is knowledge
just as anciently acquired, and as perfectly, as the power of
digestion. This colour was produced under the influence of light —
so it is even in opaque animals.

With a knowledge so far reaching, we might expect that even in
opaque animals the colouring would still follow structural lines, and
there should still be traces of this, more or less distinct.

This is precisely what we do find ; and, moreover, we sometimes
get a very fair drawing of the important hidden parts, even where
least expected, as in a cat's head, a snake's body, a dragon-fly's
thorax, a spider's abdomen, a bird's skull.

98 Colouration in Animals and Plants.

But if animals thus learned to paint themselves in definite
patterns, we might expect that when called upon to decorate for the
sake of beauty certain parts not structurally emphatic, they would
adopt well-known patterns, and hence arose the law of repetition.

But with wider experience came greater powers, and the necessity
for protection arising, the well-known patterns were enlarged, till an
uniform tint is produced, as in the Java pig, or some repeated at the
expense of others, as in the civets. But so ingrained is the tendency
to structural decoration that even where modification has reached
its highest level, as in the leaf-butterflies, some trace of the plan that
the new pattern was founded on is recognisable, just as the rec-
tangular basis can be traced in the arabesque ornaments of the
Alhambra.

The pointing out of this great fact has seemed to us a useful
addition to the great law of evolution. It supplements it; it gives a
reason why.

Could he who first saw these points have read these final pages,
it would have lightened the responsibility of the one upon whom the
completion of the work has fallen. But he died when the work was
nearly finished. The investigation is of necessity incomplete, but
nothing bears such misstatements as truth, and though specialists
may demur to certain points, the fundamental arguments will
probably remain intact.

GLOSSARY.

ACETABULA. Lat. acetabuluiii, a little vessel. Sucking discs as on the tentacles

of Physalia.

AOETA. Gr. The chief artery.
CEPHALOTHORAX. Gr. kephale, head; thorax, chest. The anterior division of

the body in Crustacea and Arachnida, composed of the amalgamated

segments of the head and thorax.
CILIA. Lat. cilium, an eyelash. Microscopic filaments having the power of

vibratory movement.
CffiNOSARC. Gr. Koinos, common ; sarx, flesh. The common stem uniting the

separate animals of compound hydrozoa, &c.
CORPUSCLE. Lat. corpusculum, a little body. Small coloured bodies, as in the

endoderm of hydra, p. 59.
DIFFERENTIATED. Modified into definite organs, or parts ; as distinct from

structureless protoplasm.
ECTODERM. Gr. ektos, outside, derma, skin. The internal layer or skin of the

Ccelenterata.
EFFERENT. Lat. effero, to carry out. A vessel which carries fluids out of the

body is said to be efferent.
ENDODERM. Gr. endon, within, derma, skin. The inner layer or skin of

Coelenterata. See ECTODERM.

ENDOSARC. Gr. endon, within, sarx, flesh. The inner layer of sponges.
EPIDERMAL. Gr. epi, upon ; derma, skin. Eelating to the outer layer of skin.

As applied to colour, surface pigment as distinct from hypodermal, or

deep-seated colour.
GASTROVASCULAR CANAL. Gr. gaster, belly, Lat. vasculum, a little vessel. The

canals or vessels in the umbrella (manubrium) of hydrozoa.
GONIDIA. Gr. gonos, offspring; oidos, like. Reproductive bodies in Sea-
anemones.
HTDRANTH. Gr. hudor, water ; anthos, flower. The bodies or polypes of

hydroids which exercise nutritive functions. They were called polypites

by Huxley.
HYDROPHTLLIA. Gr. hudor and phyllon, a leaf. Leaf -like organs protecting the

polypites of hydrozoa.

HYDROSOMA.. Gr. hudor and soma, body. The entire organism of a hydrozoon,
HYPODERMAL. Gr. hypo, beneath ; derma, skin. In colour, such as lies beneath

the surface, as distinct from epidermal.

F

100 GLOSSARY.

LYTHOCYSTS. Gr. lythos, stone, kystis, a bladder. Sense organs in hydroids,

consisting of transparent capsules inclosing round transparent concretions.
MANUBBIUM. Lat. a handle. The central polypite suspended from the interior

of the umbrella of hydroids.
MESODEEM. Gr. mesos, intermediate ; derma, skin. The middle layer of

sponges, &c.
MESOTHOBAX. Gr. mesos and thorax. The middle division of the thorax in

insects, carrying the second pair of legs.
PEEISTOME. Gr. peri, about ; stoma, a mouth. The area surrounding the mouth

in sea-anemones.
PNEUMATOCYST. Gr. pneuma, air ; Tcystis a bladder. The air-sac contained in

the pneumatophore, see below.
PNEUMATOPHOBE. Gr. pneuma ; phero, to carry. The float of certain hydrozoa

(Physophoridce.)
POLYPITE. Gr. polus, many ; pous, foot. The separate animal or zooid of a

hydrozoon. See HYDEANTH.
PBOTOPLASM. Gr. protos, first ; plasso, I mould. The jelly-like matter which

forms the basis of all tissues. It is identical with the sarcode or flesh of

protozoa.

SAC. Lat. saccus, a bag, a small cell.
SAECODE. Gr. sarx, flesh ; eidos, form. The protoplasm of protozoa, &c.,

which see.
SPADIX. Lat. spadix, a broken palm branch. In zoology a hollow process

occupying the axis of the generative buds of hydrozoa.

SPOBOSAC. Gr. spora, a seed, and sac. The body containing the ova of hydrozoa.
SOMATIC FLUID. Gr. soma, the body. The fluid which contains digested food,

and taking the place of blood, circulates through the body of hydrozoa.
TENTACLES. Lat. tentaculus, a little arm. The arms or prehensile organs of Sea-
anemones, &c.
THEEAD CELLS. Cells containing an extensible microscopic thread, possessing

stinging properties, common among the Ccelenterata.
THORAX. Gr. a breastplate. The chest.

INDEX.

PA

A. l)ylo> ... ... ... ...

.GB

63
57
66
54
57
52
77
64
77
67
79
54
60
36
56
89
57
65
67
52
36
49
95
93
41
42
42
43
42
42
46
81
82
45
79
45

P4

GE

69
57
91
69
84
8j
35
9
64

93
95
89
90
79
%
82
14
16
5
54
G6
67
69

15

36
79
74
30
77
95
90
03
4

Acanthometra
Actinea Oari, varieties of
mcsembryanthemum
Acanthostratus
Actinozoa ... ... ... 51,

Arachnocorys
Argus Pheasant 6,39,
Argynnis Lathonia .. .
Armadillo ... ... ... ...

Arthropoda, colouration of

Agalma breve
Agrion puella
Aiptasia mutabilis ...
Albinism in butterflies
AlcyonctrifK . ... ... ...

Automatic habits ...
Arthorybia rosacea...

Allman, Prof., on Hydroids 59,
"Alps and Sanctuaries" quoted...

Birds, colouration of

Biston betularia
Black and White, production of...
Blackwell, J., on British Spiders
Blatta ... ... ... ...

Amphilonche
Andres, Dr., on Hydrozoa
Anemonia sulcata
Anemones, Sea
Animals and Plants, origin of ...

Bougainvillea
Bower Birds

Bunodes crassicornis

Ancechtochilua

Burnet Moths 5,
Butler S., on inherited
memory ... 9, 10, 11,
- • — - on oricrin of animals

Anthocaris belemia

euphemoides ...

and plants
Butterflies, albinism in
, .. — , — classification of

Apatura iris

larvae ot

Araschnia Levana 43,
. porima ... ... 43,45,
prorsa .. ... 43,

Calycophoridce
Carcinus mcenas

102

INDEX.

PJ
Carpocanium
Cats, colouration of ... 17,
recognising form ...
Caterpillars, colours of

LOE

57
92
32
81
22
87
86
88
59
77
57
49
74
20
51
57
79
79
55
95
32
53
72
91
73
25

69
53
32
28
3
51
4
85
59
68
49
85
94
51
82
88
5
3
91

Cephalopoda
Cerithium

Char

Chlorophyll in hydra
Cicada

Cladococeus ...

Classification of animals...

Ccelenterata

Coslodendrum
Ccenonympha davus

Ccenosarc

Colette ... ...

Colour and form

epidermal

— • - following structure 83,

- hypodernial . . . 53,

of day-and-nighl flying
insects 47,

opaque

- perception of ...5, 23, 25,
• uniform, why rare
Colouration

of insects

— of protozoa

Contour feathers ...

Conus ...

Coppinia arcta

Corallium rulrum

Corals

Correlation of teeth and hair

PAGE
86

. 60

. 54

. 54

94

Corynida ... ... ... ... 52

Cowries ... ... 86

Crab, shore ... 4

Croton 46

Cuttle-fishes 19, 87

Cyllo leda ... ... ... ... 45

Cynthia cardui ... ... ... 68

Cyprcea ... ... ... ... 86

Cyrtidosphcera 57

Dallas, "W.S., on butterflies ... 71
Danais ... ... ... ... 72

niavius 30,80

Darwin, C.

1, 2, 5, 9, 11, 14, 45, 47, 94

Darwin, Dr. E., cited 37

Deer 92

Deformity, antipathy to 32

Deilephila Euplwrlice 81

Descent with modification ... 1

Desert animals, colour of ... 4

Dictyoceras ... ... ... ... 57

Dictyophimus 57

Diphyes 63

Disease, markings in ... 39, 44
Distant, W. L., on Malayan butter-
flies 80

Distinctive Colouration 3

Dogs recognising portraits ... 32

Draccena ferrea ... ... 96

Elephant, increase of 2

Engelmann on Euglena 34

Epidermal colour 72

Eresus cinnabarinus ... ... 82

Eucecryphalus ... ... ... 57

Eucrytidium ... ... 57

Euglena viridis ... ... 34

Evolution ... ... ... ,..1-98

Eye-spots 45; 47

INDEX.

103

Fayrer, Sir W., on snakes
Feathers

PAGE

... 89
... 91

PJ
Kallima inachtts ... ... 30,
Kentish Glory Moth

Lamium galeobdolon
Lankester, Prof. Bay, on develop-
ment of eyes
Large Copper Butterfly
Larvae, colours of 45,
Laws of emphasis ...

i.GE

80
30

96

97
68
81
21
18
2
2
22
18
2
30
56
92
41
41
9
26
33
25
43
92
46
62
65
68
83
83
83
84
83
84
84
84
83

88

86
87
54

92

Fishes, colours of
Foal, stripes on
Foraminiferce
Fuller, W. J., on aquatic larvae

Gamopetalous flowers
Gegenbaur's " Comparative
Anatomy " cited
General colouration

Gloxinia

... 88
... 46
... 56

... 77

... 96

... 82
... 3
96

multiplication

Gomphina . . .

... 77

repetition ... 21,

Gonepteryx Cleopatra

41,42
40,42
... 52
... 79
... 56
... 91

53, 72

8

structure...

Gonophores
Grapta interrogationis
Gregarinidce
Guinea-fowl

Haagen, Dr., on colour ...

Leaf-butterfly 16,
Leidy, Prof., on Rhizopoda
Leopard 17,

Leucophasia diniensis

' ' Life and Habit ' ' cited
Light, reflected

Haeckel, Prof., on Radiolaria
Hair and teeth, correlation of
Hawk moths
Hebrides, colours of insects in

... 57
... 94
... 69

... 80
2

Liminitia sibilla ...
Lion 17,
stripes on young
Lithocysts of hydroids ...
Lucernaria auricula
Lyccena dispar
Lycosa agretyca

Herpes
Heteromorphism ...
Higgins, Rev. H. H.
Hoverer flies
Hummingbirds
Hutchinson, Mr., on herpes
Huxley, Prof., on hydrozoa
Hydra viridis

40, 93
... 78
... 39
... 84
90, 92
... 40
... 63
... 59
.w

latitans ... ... ...

Hydrozoa ... ... ... 51, 59

Hypodermal colour ... 53, 72

Identity of offspring and parent. . . 11
Identity, personal... ... ... 10
Inherited memory... ... ... 8
Insects, colour in 68,75

John Dory --- 89

picta

rapax

• stultorum
Madrepores
Mammalia, colouration in

104

INDEX.

Margarita catenata

Measles

Medusae

Melanism in insects

PAGE

... 87

... 39

52, 65

79

Meldola, Prof. E., on Melanism 79

Melitcea artemis ... ... ... 43

athalia 43

Mimicry 3, 4

MoUusca 21

colouration in ... ... 85

Monstrosities, antipathy to ... 32

Morphines 72

Morpho 4

Murex ... ... ... ... 86

Muscles of insects 71

Nectarinea chloropygea 90

Newman, Mr., on varieties of

butterflies 77

Newts 89

Nitzsch on feather- tracts ... 91

Nudibranchs ... ... ... 85

Nymphalidce 74

Oak Egger Moth

Ocelli

Ocelot

Oliva

Opaque colouring

Organ-pipe coral

Origin of animals and plants

species ...

Orthopoacilism

Oxen

30
47
93
86
53
54
36
1

78
94

Painted Lady Butterfly

... 68

12

79

43, 68, 76, 78

larva of 81

30, 76, 80

14

podalirius 43

Paradisea Papuana ... 90

Papilio Ajax
machaon

merope

nireua

Paradiaea regia

speciosa ...

Wallacei

• Wilsoni . . .

Pavetta Borlonica ... ...

Pecten ... ... ...

Pelargonium ... ...

Perch

Personal identity ......

Physalia ... ... ... ... 63

PAGE
90
90
90

90, 91
.. 96
.. 86
.. 96
88
.. 10

caravilla

pelagica ...

utriculus.,.

64

64

64

PhysophoridcB ... ... ... 63

Plaice 88

Plants and animals, origin of ... 36

colour in ... ... ... 95

Pneumatophores ... ... ... 63

Portuguese Man o' War 63

Protective resemblance ... ... 3

Protista ... 34

Protozoa 20

colouration in ... 51, 56

Python 89

Radiolaria ... ... ... ... 57

Earity of uniform colour 28

Eay Lankester, Prof., on Asci-

dians 35

Eed Admiral Butterfly 29

Eepetition, effects of ... ... 8

Eeptilia, colouration in 89

Eesemblance, Protective 3

Rhizophora filiformis ... ... 64

Mhizopoda ... ... ... ... 55

Ehododendron 96

Einglet Butterflies, eye-spots of... 47

Eoach ... .. 88

Eomanes, Prof., cited ... 33, 34

Satyrus hyperanthus 79

Scales of insects, structure of . . 72

Scarlet Tiger Moth 5

Sea anemones ... 52

colours of ... 67

INDEX.

105

Seasonal dimorphism
Sea squirts ...
Segestria aenoculata
Selection, sexual ...
Self-coloured flowers
Sense organs of Butterflies
Sertularidos

Sexual colours

selection

dimorphism

Shell, Structure of

Shore Crab...

Simple variation in Butterflies

Siphonophora

Smallpox

Snakes, patterns of
Sollas, Prof., on Sponges

Soles

Sparassus smaragdulus

Species, origin of

Sphceronectes

Sphingidce ...

Spiders, structure and colour of

Spiracles of larvae

Spondylus ...

Sponges

Spongida ... ...

Spongocyclia

Spots and S tripes

Stephanomia amphitridis ...
Struggle for existence

Sun-birds

Sus vittatua...

Sutton, Mr. Bland, on Herpes
Swallow-tailed Butterflies
Syncoryne pulchella
Systems of colouration ...

Teeth and Hair, correlation of
Thomisus cinereus ...
floricolens

PAGE

... 70

... 35

... 83

... 5

,.. 28

... 30

... 63

... 4

5

... 70

. . 85

4

,.. 77

,.. 63

.. 39

... 89

... 58

,.. 88

... 82

... 1

,.. 63

45, 69
... 82
,.. 22
... 86
... 57
.. 57
,.. 57
,.. 39
... 63
... 2
... 90

46, 94
... 40
... 68
... 62
... 51

... 94

... 82
82

Thomisua luctuosus . . .
trux

PAGE
.. 84
. 82
2

17,92
.. 69
.. 33
90, 92
53

Thrush, increase of

Tiger

Moths

Tipula ... ... ...

Toucans

Transparency and colour...

Trigonia 86

Tubipora musica 54

Tubularida... ... ... ... 59

Tylor, A., on Specific change ... 10

Vanessa Antiopa 76

atalanta 29,43,69

urticce 77

Variation in insects . .. . .. 70

law of 2

simple, in Butterflies ... 77

Velella 52, 65

Vertebrata, colouration of ... 88

Viverridos ... ... ... ... 94

Wallace, A. E., on sexual selec-
tion ...5, 6, 14, 15

on colour ... ... 29

on abnormal struc-
tures 94

Warning colours 4

Wasps 84

Weir, J. Jenner, on variation in

insects ... ... ... ... 78

Weismann, Dr., on Caterpillars... 81

Wing of Butterfly, typical ... 70

patterns of 76

Woodpecker 91

Yellow Archangel...

96

Zebra 92

Zygcena 69

Fig. 4. — PYTHON.
Showing vertebra-like markings.

Q

Fig. 5. — TIGER.
The pattern changes at the points lettered.

Q-

Fig. 6.— TIGER.

W

co

Fig. 9. — LEOPARD.
The pattern changes at the points lettered.

Fig. 10. — LEOPARD.
The pattern changes at the points lettered.

Figs. 11, 12. — LEOPARDS' HEADS.

Fig. 13. — LYNX.
The colour changes at the points lettered.

Fig. 14. — LYNX.

R

15. — OCELOT.

Showing changes of pattern at the joints, $c., with enlargement of

head-pattern.

Fig. 16. — BADGER.
The colour changes at the point* lettered.

Fig. 17. — BEGONIA LEAF.

000047179 7