THE COLOURATION OF INSECTS.
(_Continued._)
_General Scheme of Colouring._ So various are the patterns displayed
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 by 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.
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_, Pl. III. Fig. 3, is a very perfect example.
The border pattern may consist of one or more rows of spots, lines,
bands, or scallops;[31] 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 Swallow-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 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.[32] 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 _Æschna_ 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 urticæ_).
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 modification of the original form. The
first striking difference is in the margin of 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 lost its scalloping. In the fore-wing some 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 pupæ from Wicken Fen, Cambridgeshire, 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 pupæ 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.[33] He divides variations into
two sections, Aberrations or Heteromorphism, and constant variations or
Orthopæcilism, and subdivides each into six classes, as under:--
_Heteromorphism._
Albinism ... ... white varieties.
Melanism ... ... black do.
Xanthism ... ... pallid do.
Sports ... ... or occasional variations not included
in the above.
Gynandrochomism ... females coloured as males.
Hermaphroditism ... sexes united.
_Orthopæcilism._
Polymorphism ... variable species.
Topomorphism ... local varieties.
Atavism ... ... reversion to older forms.
Dimorphism ... ... two constant forms.
Trimorphism ... ... three do. do.
Horeomorphism ... seasonal variation.
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 (_Cænonympha
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.[34]
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 convertible into one another, would in
itself be sufficient to show that in these cases there is no departure
from the general law. In _Grapta interrogationis_, 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.
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 Rhopalocera 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 Pieridæ--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.
[Illustration: Plate VII.
CATERPILLARS.]
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 caterpillar 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. Euphorbiæ_, 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 larvæ 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 larvæ possess horns either upon the head, as in _Apatura iris_ and
_Papilio machaon_, or on the tail, as in many of the sphyngidæ, 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 _euphorbiæ_, 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.
[Illustration]
[31] In the true scallop pattern the convexity is turned towards the
body of the insect.
[32] J. W. Fuller on the Breathing Apparatus of Aquatic Larvæ. Proc.
Bristol Nat. Soc.
[33] Entomologist, vol. xvi., p. 169, 1883.
[34] Nature. R. Meldola on Melanism, 1885.
CHAPTER XII.
ARACHNIDA.
The Arachnida 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 segmentation. 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.[35]
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 represented in
Blackwell's work,[36] 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.
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 propriety 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, Pl. 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 posteriorly; 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_, Fig.
13, where the chamber-markings are almost obliterated, and merely an
irregular stripe left. The stages by which this modification 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_, _fluviatilis_, _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 effect that
internal structure may have upon external decoration.[37]
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.
[Illustration: Plate VIII.
SPIDERS.]
[35] Elements of Comparative Anatomy, by C. Gegenbaur. Translated by
Jeffrey Bell and Ray Lankester, 1878, p. 285.
[36] Spiders of Great Britain and Ireland, J. Blackwell. Ray. Soc.,
1861.
[37] The decoration of many of the Hoverer flies and wasps is of a
similar character.
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 antennæ 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 regionally, 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 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 mollusca 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 (_Cypræa_), the mantle is reflexed so as
to meet along the median line, where we see the darkest colour.
The rule amongst spiral shells is to possess spiral and 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
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.
[Illustration]
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
marked by a dark line. These facts point distinctly to structural
decoration.
[Illustration: Plate IX.
CHAR AND PERCH.]
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 colouring
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 vertebræ, 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 sternum 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 breastbone, 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 (Trochilidæ), and Sun Birds (Nectarinidæ). 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.
Parietal bones green.
Occiput yellow.
A beautiful ruff emphasizes the pectoral muscles, and the tail
appendages emphasize the share-like caudal vertebræ.
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.
[Illustration: Plate X.
SUN BIRDS.]
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 decoration is not
uniform, but the sizes and axes of the spots change slightly as they
occupy different regions; as may be seen in Woodpeckers 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 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 vertebræ, and still follow the lines
of the ribs. In the tiger the decoration changes at the neck, and on the
head, and the cervical vertebræ are often indicated by seven stripes.
See Fig. 5.
The markings over the vertebræ 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 decreasing 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 marking 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, 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
Viverridæ, 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 suppression 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 viverridæ. 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 viverridæ, 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.
[Illustration: Plate XI.
LEAVES.]
CHAPTER XV.
THE COLOURATION OF PLANTS.
The general structure of plants is so simple in comparison with 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, Caladiums, 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 decolouration 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, in the
_Calatheas_ we have dark marks running along the veins. In _Dracæna
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 _Pelargoniums_ 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.
[Illustration: 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 transparent 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.
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 rectangular
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.
[Illustration: FINIS.]
GLOSSARY.
ACETABULA. Lat. _acetabulum_, a little vessel. Sucking discs as on
the tentacles of _Physalia_.
AORTA. 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.
C[OE]NOSARC. 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 Coelenterata.
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. Relating 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.
HYDRANTH. Gr. _hudor_, water; _anthos_, flower. The bodies or
polypes of hydroids which exercise nutritive functions. They were
called polypites by Huxley.
HYDROPHYLLIA. 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
hydrozöon.
HYPODERMAL. Gr. _hypo_, beneath; _derma_, skin. In colour, such as
lies beneath the surface, as distinct from epidermal.
LYTHOCYSTS. Gr. _lythos_, stone, _kystis_, a bladder. Sense organs
in hydroids, consisting of transparent capsules inclosing round
transparent concretions.
MANUBRIUM. Lat. a handle. The central polypite suspended from the
interior of the umbrella of hydroids.
MESODERM. Gr. _mesos_, intermediate; _derma_, skin. The middle
layer of sponges, &c.
MESOTHORAX. Gr. _mesos_ and _thorax_. The middle division of the
thorax in insects, carrying the second pair of legs.
PERISTOME. Gr. _peri_, about; _stoma_, a mouth. The area
surrounding the mouth in sea-anemones.
PNEUMATOCYST. Gr. _pneuma_, air; _kystis_ a bladder. The air-sac
contained in the pneumatophore, see below.
PNEUMATOPHORE. Gr. _pneuma_; _phero_, to carry. The float of
certain hydrozoa (_Physophoridæ_.)
POLYPITE. Gr. _polus_, many; _pous_, foot. The separate animal or
zöoid of a hydrozöon. _See_ HYDRANTH.
PROTOPLASM. 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.
SARCODE. 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.
SPOROSAC. 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.
THREAD CELLS. Cells containing an extensible microscopic thread,
possessing stinging properties, common among the _Coelenterata_.
THORAX. Gr. a breastplate. The chest.
INDEX.
PAGE
_Abyla_ 63
_Acanthometra_ 57
_Actinea Cari_, varieties of 66
---- _mesembryanthemum_ 54
_Acanthostratus_ 57
_Actinozoa_ 51, 52
_Æschna_ 77
_Agalma breve_ 64
_Agrion puella_ 77
_Aiptasia mutabilis_ 67
Albinism in butterflies 79
_Alcyonariæ_ 54
Allman, Prof., on Hydroids 59, 60
"Alps and Sanctuaries" quoted 36
_Amoeba_ 56
Amphibia 89
_Amphilonche_ 57
Andres, Dr., on Hydrozoa 65
_Anemonia sulcata_ 67
Anemones, Sea 52
Animals and Plants, origin of 36
---- classification of 49
_Anoechtochilus_ 95
Anteater 93
_Anthocaris belemia_ 41
---- _belia_ 42
---- _cardamines_ 41, 42
---- _euphemoides_ 43
---- _eupheno_ 42
---- _simplonia_ 42
_Apatura iris_ 46
---- larvæ of 81
_Arachnida_ 82
_Araschnia Levana_ 43, 45
---- _porima_ 43, 45, 79
---- _prorsa_ 43, 45
_Arctia_ 69
_Arachnocorys_ 57
Argus Pheasant 6, 39, 91
_Argynnis Lathonia_ 69
Armadillo 84
Arthropoda, colouration of 85
Ascidians 35
Automatic habits 9
_Arthorybia rosacea_ 64
Badger 93
_Begonia_ 95
Birds, colouration of 89
---- of Paradise 90
_Biston betularia_ 79
Black and White, production of 28
Blackwell, J., on British Spiders 82
_Blatta_ 14
Bougainvillea 16
Bower Birds 5
_Bunodes crassicornis_ 54
---- _gemmaceus_, varieties of 66
---- _rigidus_ 67
Burnet Moths 5, 69
Butler S., on inherited memory 9, 10, 11, 15
---- on origin of animals and plants 36
Butterflies, albinism in 79
---- classification of 74
---- sense organs of 30
---- varieties of 77
_Caladium_ 95
_Calathea_ 96
_Calycophoridæ_ 63
_Carcinus moenas_ 4
_Carpocanium_ 57
Cats, colouration of 17, 92
---- recognising form 32
Caterpillars, colours of 81
---- spiracular markings 22
_Cephalopoda_ 87
_Cerithium_ 86
Char 88
Chlorophyll in hydra 59
Cicada 77
_Cladococeus_ 57
Classification of animals 49
---- of butterflies 74
_Coelenterata_ 20
---- colouration in 51
_Coelodendrum_ 57
_Coenonympha davus_ 79
---- _pamphilus_ 79
Coenosarc 55
_Coleus_ 95
Colour and form 32
---- and transparency 53
---- epidermal 72
---- following structure 83, 91
---- hypodermal 53, 73
---- nature of 25
---- of day-and-night flying insects 47, 69
---- opaque 53
---- perception of 5, 23, 25, 32
---- uniform, why rare 28
Colouration 3
---- laws of 21, 51
---- of desert animals 4
---- of arthropoda 85
---- of coelenterata 51, 59
---- of insects 68
---- of invertebrata 49
---- of molluscs 85
---- of plants 94
---- of protozoa 51
---- of spiders 82
---- of vertebrata 88
---- sexual 5
---- varieties of 3
Contour feathers 91
_Conus_ 86
_Coppinia arcta_ 60
_Corallium rubrum_ 54
Corals 54
Correlation of teeth and hair 94
_Corynida_ 52
Cowries 86
Crab, shore 4
Croton 46
Cuttle-fishes 19, 87
_Cyllo leda_ 45
_Cynthia cardui_ 68
_Cypræa_ 86
_Cyrtidosphæra_ 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 Euphorbiæ_ 81
---- _galii_ 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 butterflies 80
Distinctive Colouration 3
Dogs recognising portraits 32
_Dracæna 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
Fayrer, Sir W., on snakes 89
Feathers 91
Fishes, colours of 88
Foal, stripes on 46
_Foraminiferæ_ 56
Fuller, W. J., on aquatic larvæ 77
Gamopetalous flowers 96
Gegenbaur's "Comparative Anatomy" cited 82
General colouration 3
_Gloxinia_ 96
_Gomphina_ 77
_Gonepteryx Cleopatra_ 41, 42
---- _rhamni_ 40, 42
Gonophores 52
_Grapta interrogationis_ 79
_Gregarinidæ_ 56
Guinea-fowl 91
Haagen, Dr., on colour 53, 72
Habits 8
Haeckel, Prof., on _Radiolaria_ 57
Hair and teeth, correlation of 94
Hawk moths 69
Hebrides, colours of insects in 80
Heredity 2
Herpes 40, 93
Heteromorphism 78
Higgins, Rev. H. H. 39
Hoverer flies 84
Humming birds 90, 92
Hutchinson, Mr., on herpes 40
Huxley, Prof., on hydrozoa 63
_Hydra viridis_ 59
_Hydrida_ 59
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
_Kallima inachus_ 30, 80
Kentish Glory Moth 30
_Lamium galeobdolon_ 96
Lankester, Prof. Ray, on development of eyes 97
Large Copper Butterfly 68
Larvæ, colours of 45, 81
Laws of emphasis 21
---- exposure 18
---- heredity 2
---- multiplication 2
---- repetition 21, 22
---- structure 18
---- variation 2
Leaf-butterfly 16, 30
Leidy, Prof., on _Rhizopoda_ 56
Leopard 17, 92
_Leucophasia diniensis_ 41
---- _sinapis_ 41
"Life and Habit" cited 9
Light, reflected 26
---- sensibility to 33
---- waves 25
_Liminitis sibilla_ 43
Lion 17, 92
---- stripes on young 46
Lithocysts of hydroids 62
_Lucernaria auricula_ 65
_Lycæna dispar_ 68
_Lycosa agretyca_ 83
---- _allodroma_ 83
---- _andrenivora_ 83
---- _cambria_ 84
---- _campestris_ 83
---- _latitans_ 84
---- _picta_ 84
---- _piratica_ 84
---- _rapax_ 83
Mackerel 88
_Mactra_ 86
---- _stultorum_ 87
Madrepores 54
Mammalia, colouration in 92
_Margarita catenata_ 87
Measles 39
Medusæ 52, 65
Melanism in insects 79
Meldola, Prof. R., on Melanism 79
_Melitæa artemis_ 43
---- _athalia_ 43
Mimicry 3, 4
Mollusca 21
---- colouration in 85
Monstrosities, antipathy to 32
_Morphinæ_ 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
_Nymphalidæ_ 74
Oak Egger Moth 30
Ocelli 47
Ocelot 93
_Oliva_ 86
Opaque colouring 53
Organ-pipe coral 54
Origin of animals and plants 36
---- -- species 1
Orthopoecilism 78
Oxen 94
Painted Lady Butterfly 68
Pangenesis 12
_Papilio Ajax_ 79
---- _machaon_ 43, 68, 76, 78
---- ---- larva of 81
---- _merope_ 30, 76, 80
---- _nireus_ 14
---- _podalirius_ 43
_Paradisea Papuana_ 90
---- _regia_ 90
---- _speciosa_ 90
---- _Wallacei_ 90
---- _Wilsoni_ 90, 91
_Pavetta Borbonica_ 96
_Pecten_ 86
Pelargonium 96
Perch 88
Personal identity 10
_Physalia_ 63
---- _caravilla_ 64
---- _pelagica_ 64
---- _utriculus_ 64
_Physophoridæ_ 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
Rarity of uniform colour 28
Ray Lankester, Prof., on Ascidians 35
Red Admiral Butterfly 29
Repetition, effects of 8
Reptilia, colouration in 89
Resemblance, Protective 3
_Rhizophora filiformis_ 64
_Rhizopoda_ 56
Rhododendron 96
Ringlet Butterflies, eye-spots of 47
Roach 88
Romanes, Prof., cited 33, 34
_Satyrus hyperanthus_ 79
Scales of insects, structure of 72
Scarlet Tiger Moth 5
Sea anemones 52
---- ---- colours of 67
Seasonal dimorphism 70
Sea squirts 35
_Segestria senoculata_ 83
Selection, sexual 5
Self-coloured flowers 28
Sense organs of Butterflies 30
_Sertularidæ_ 63
Sexual colours 4
---- selection 5
---- dimorphism 70
Shell, Structure of 85
Shore Crab 4
Simple variation in Butterflies 77
_Siphonophora_ 63
Small pox 39
Snakes, patterns of 89
Sollas, Prof., on Sponges 58
Soles 88
_Sparassus smaragdulus_ 82
Species, origin of 1
_Sphæronectes_ 63
_Sphingidæ_ 45, 69
Spiders, structure and colour of 82
Spiracles of larvæ 22
_Spondylus_ 86
Sponges 57
_Spongida_ 57
_Spongocyclia_ 57
Spots and Stripes 39
_Stephanomia amphitridis_ 63
Struggle for existence 2
Sun-birds 90
_Sus vittatus_ 46, 94
Sutton, Mr. Bland, on Herpes 40
Swallow-tailed Butterflies 68
_Syncoryne pulchella_ 62
Systems of colouration 51
Teeth and Hair, correlation of 94
_Thomisus cinereus_ 82
---- _floricolens_ 82
_Thomisus luctuosus_ 84
---- _trux_ 82
Thrush, increase of 2
Tiger 17, 92
---- Moths 69
_Tipula_ 33
Toucans 90, 92
Transparency and colour 53
_Trigonia_ 86
_Tubipora musica_ 54
_Tubularida_ 59
Tylor, A., on Specific change 10
_Vanessa Antiopa_ 76
---- _atalanta_ 29, 43, 69
---- _urticæ_ 77
Variation in insects 70
---- law of 2
---- simple, in Butterflies 77
_Velella_ 52, 65
Vertebrata, colouration of 88
_Viverridæ_ 94
Wallace, A. R., on sexual selection 5, 6, 14, 15
---- on colour 29
---- on abnormal structures 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
_Zygæna_ 69
[Illustration]
[Illustration: Fig. 4.--PYTHON.
_Showing vertebra-like markings._]
[Illustration: Fig. 5.--TIGER.
_The pattern changes at the points lettered._]
[Illustration: Fig. 6.--TIGER.]
[Illustration: Fig. 7.--TIGER.
_Showing supra-orbital nerve mark._]
[Illustration: Fig. 8.--TIGER.
_Showing cerebral markings, and markings over
nerves near the eyes._]
[Illustration: Fig. 9.--LEOPARD.
_The pattern changes at the points lettered._]
[Illustration: Fig. 10.--LEOPARD.
_The pattern changes at the points lettered._]
[Illustration: Figs. 11, 12.--LEOPARDS' HEADS.]
[Illustration: Fig. 13.--LYNX.
_The colour changes at the points lettered._]
[Illustration: Fig. 14.--LYNX.]
[Illustration: Fig. 15.--OCELOT.
_Showing changes of pattern at the joints, &c.,
with enlargement of head-pattern._]
[Illustration: Fig. 16.--BADGER.
_The colour changes at the points lettered._]
[Illustration: Fig. 17.--BEGONIA LEAF.]
Transcriber's Notes:
Variations in spelling, punctuation and hyphenation have been retained
except in obvious cases of typographical error.
"Haeckel" and "Hæckel" were used interchangeably and have been
standardized to "Haeckel".
Image tags interrupting paragraphs have been moved.
Footnotes have been moved to end of chapters.
End of Project Gutenberg's Colouration in Animals and Plants, by Alfred Tylor