Reptiles do only a little in the way of display. The male newt gets a crest in the spring like the wanton lapwing of Tennyson, and a splendid orange-red colour on the belly. Male fishes often develop "display" colours at the breeding season, and it is a mistake to suppose that their eyes and brains are not sensitive to colour. We have a familiar instance in the male of our common little stickleback, who, in early summer, builds, in his native pond, his nest of fragments of weed cemented together, with a wide entrance and a back door. He then becomes brilliant blood-red on the belly (he was white before) and dark green on the back, and swims about near the nest, and has an occasional fight with a competitive neighbour, whilst hustling and shepherding any female stickleback he may meet so as to make her enter it. She enters it alone, and lays an egg, or, perhaps, two or three, and then goes out by the back-door! The male, well pleased, at once goes into the nest, fertilizes the eggs, and swims out again to get another contribution to his future family. After several females have thus deposited eggs in his nest, and he has fertilized them, he keeps guard for many days whilst the young are developing. Even when they are hatched he is in constant attendance on them, for there is danger of their being eaten—not by other males, who are as busy as he is, but by the emancipated females, who neither build the nest nor care for the young, but just lay an egg here and an egg there when invited, and pursue a selfish life of amusement and voracious feeding.
It is still doubtful how far male insects of the true six-legged group appeal to the females by colour-display, even when they are brightly coloured, or in other ways than by perfumes (which they do very generally), but among the spiders there are some kinds (not common ones) in which the males have on the front of the body one or two extraordinarily brilliant spots of colour (red, apple-green, or yellow). The male moves round the female in courtship, and poses himself in most curious attitudes, so as to exhibit the brilliant colour to her; forcing it, as it were, on her attention. In other species of spiders the male dances and circles round the female, making curious and definite antics. Some spiders also have rasp-like organs, with which they can make a kind of singing note, which appears to fascinate the other sex. The vibration of a tuning-fork will cause some spiders to dance! In most spiders the female is much larger than the male—in some cases, ten times as large—and the approach of the male to the female is a dangerous business for him, for usually after his embrace she turns on him, kills him, and eats him. This is almost a unique case amongst animals (though ancient legends tell of princesses of similar ferocity), and curiously enough is not invariable among all species of spider. In some the males and females are quite friendly. The ogre-like habit of female spiders is not so injurious a thing as it may appear. For the most nourishing food is thus afforded to the female who has to ripen her eggs, and take care of her young, whilst, if the male escapes, it appears that he is short-lived and very soon dies. This cannibal tendency is very strongly developed also in the allied group, the scorpions. Two hundred scorpions were left in a cage in the South of France, whilst the naturalist (Maupertuis) who had placed them there was obliged to go to Paris. On his return he found one large, very plump and active scorpion in the box, surrounded by legs and hard bits of the bodies of the rest. The survivor was in the position of Gilbert's ancient mariner, who said that he was "the cook and the mate, and the captain's boy and the crew of the Nancy Bell." Scorpions do not perform any courtship display. The males and females are of equal size, and dance together, holding one another by their large claws, before mating and retiring into a burrow.
Cuttle-fishes, squids, and the octopus—called Cephalopods—were considered by Aristotle to be the spiders of the sea. It is curious how they not only have a superficial resemblance of form to spiders, but in some habits are like them, though the Cephalopods are molluscs allied to snails and mussels, and are quite unlike spiders in deeper structure and remote from the whole group of hard-skinned, jointed-legged animals such as crustaceans, spiders, and insects. I once had the chance to see a male octopus "displaying" to a female in one of the tanks of the aquarium at Naples. There were a male and a female already living there when we introduced from another tank a second male, which had just destroyed and fed upon a large lobster, who had himself, with no evil purpose, crushed the head of a Mediterranean turtle foolishly placed by that animal between the open fingers of the lobster's big nippers. The new arrival promptly drove the earlier tenant octopus out of the tank. He pursued his rival round and round with great rapidity until the latter leapt from the surface of the water (by a violent contraction of the mantle) and escaped into the adjacent tank. Then the triumphant intruder approached the female—floods of changing colour, reddish-brown, purple, and yellow, passing over the surface of his body—and commenced an extraordinary display with his eight long sucker-bearing arms. He made these wind into close-set flat spirals and again unwind and gracefully trail in the water, when they immediately wound up again in spiral coils. The female watched this proceeding for more than an hour, and then they embraced. I could not follow any further details, but a few days after this the female piled up a number of stones, so as to make a nest in shape like a shallow basin. We enticed the male into a net and placed him in another tank, so that he should not be able to molest the female or to devour her offspring, which he would do if he had the chance. Then the female laid her eggs—minute oval, transparent bodies, each with a long stalk and all joined on to a common branching stem: the whole resembled a head of millet seed. The female tended her eggs by continually pumping a stream of water over them, and could not be driven from them. She fought savagely and heroically in their defence. But I succeeded in enticing her into a net by aid of a toothsome crab, and then took a few—only a few—of the cherished eggs, and replaced their mother in the tank, where she at once resumed the "incubation" of her eggs. For it is an "incubation," although one in which oxygenated water, and not warmth, is the accompaniment of the sitting of the "hen." I was able to watch the development of the young within the transparent eggs, which I kept in a stream of fresh sea-water, and I published a short account of what was novel in the growth of these embryos. It had not been studied previously, nor have I seen any later account of the development of octopus. The true cuttle-fish, with the hard oblong shell sunk in the back, lays each egg in a dark leathery shell. They look like small grapes, and are left, thus protected, to their fate. They have been studied, both before I obtained octopus eggs and since, in great detail. The "squid" embeds her eggs, many together, in bunches of long fingers of colourless jelly. Only the octopus and the argonaut, among Cephalopods, are known to give maternal care and incubation to their eggs.
CHAPTER XXIII
COURTSHIP, INSTINCT AND REASON
APART from the familiar instances of male colour-decoration afforded by birds, we find that even some of the minute water-fleas inhabiting freshwater lakes and the sea, and known as Crustacea Entomostraca, put on a courting dress at the breeding season; that is to say, the males become brilliantly coloured with patches of red and blue. And among the highest mammals we find that the same colours are, in some cases, displayed by the males as a fascination to the females. This is the case with the males of some of the baboons, though not with those of the highest man-like apes, who, like the primitive "savage" man, have no decoration, no pretty seductive ways appealing to either the eye or the ear, but rely on their strength and ferocity to overawe and paralyze the female. In the male "mandrill" baboon the skin of the sides of the great snout is of a deep blue colour, whilst the nose and a tract behind it is wax-like and bright red. Not only that, but the buttocks are brilliantly coloured, a central red area passing at the sides through rich purple to pale blue. The animal, which is often to be seen in menageries, is evidently proud of this finely-coloured region of his body, and turns it to a visitor and remains quietly posed, so that it may be well seen and duly admired. The hind-quarters of other monkeys, both male and female, show a brilliant red colouring during the mating season, and the skin and hair of the face is variously coloured, so as to produce a decorative pattern (eyebrows, moustache, beard, nose, all strongly contrasted in colour) in the smaller monkeys, usually more strikingly in the males than in the females. A brilliant emerald-green patch of colour is shown in the hinder part of the body of the male in one species sometimes to be seen at Regent's Park.
The making of sounds is a capacity possessed by many animals, small and big. Often it seems to have no particular significance, but, as in the case of the "humming" of bees and flies and the "droning" of beetles, is the necessary accompaniment of the vibration of the wings. But many animals make sounds as a "call," either to other individuals of their species, irrespective of sex, or more definitely as signals and appeals to the other sex, just as the luminosity which happens to accompany certain necessary chemical activities in the bodies of the lower animals has become specialized and utilized in the glow-worm and other higher forms as a signal and appeal. The rubbing of rough surfaces against one another is developed into a "stridulating organ" which we find in crickets, locusts, scorpions, spiders, and even in marine crustacea, and it is often specialized as a sexual appeal. The mere production of sound by tapping against wood is used by the little beetle, the death-watch, as a call, and is responded to by his mate with similar tapping. Such "tapping" is developed into a remarkable rhythmic vibrating sound by the birds called woodpeckers, and has its significance in courtship. But it is chiefly by the inspiration and expiration of air over vibrating cords or membranes called "vocal organs" that animals produce distinctive and musical sounds. In most cases such animals have a more general and simple "cry," which is not necessarily a sexual appeal, but addressed to comrades generally, and also a more elaborate cry or song which is primarily used by the male as an attraction in courtship, but has in the case of many birds been inherited from original male singers by the females also. The "singing" of birds—apart from simpler cries and calls—is a sexual address, an act of courtship. It is a display of power and capacity on the part of the male, and that such is its character is shown by the competition between male birds in the endeavour to "out-sing" one another. Some birds become extraordinarily excited in these competitions, which take the place of actual fighting, the victor who silences his opponents being the winner of the female bird, who is at hand listening to the competition. Caged chaffinches are celebrated for their eagerness to compete with one another in singing. They deliver their little song alternately until one is exhausted and unable to take up his turn. He is vanquished. So excited do the birds become that it occasionally happens that one of the competitors drops down dead. The beginning and directive causes of the particular song of different kinds of birds is not understood. But it is well known that they have a great gift of imitation. Parrots, piping crows, ravens, and other such birds are familiar instances, whilst little birds such as bullfinches can be trained to whistle the melodies which human beings have invented. Even the house-sparrow, which, though allied to singing finches, never sings at all when in natural conditions, has been converted into a songster by bringing it up in company with piping bullfinches.
Other animals which cannot sing like the birds yet use their voices in courtship. The frogs and toads are no mean performers in this way, whilst cats, deer, and other large animals are "singers," of a kind, when stirred by mate-hunger. The monkeys chatter and make various vocal sounds, but the gibbons and man-like apes produce excessively loud and penetrating cries. These cries, though sometimes of fine note and repeated rhythmically (as in the gibbons and chimpanzees), have not the character of song. The beginnings of song in mankind are lost in the mist of ages. The Australian black-fellows chant and dance with rhythmic precision and a certain kind of melancholy cadence, but they never attempt to fascinate the other sex by the use of the voice (nor, so far as is known, in any other way), and, indeed, there is a vast interval between their vocal performances and the love-songs of modern civilized races. Man has not inherited singing from his animal ancestry, but has re-invented it for himself. His real knowledge and command of "music" is actually a novelty which has sprung into existence within the last few hundred years.
There is no doubt that animals of the same species are attracted to one another by smell, and that distinct species have distinct smells. Further, there is no doubt that in many cases the special smell of either sex attracts the other. But modern man has so nearly lost the sense of smell—why it is difficult to say, excepting that it is because it was not of life-saving value to him—that it is very difficult for us to estimate properly the significance of perfumes and odours. We know that the dog has what to us seems a marvellous power of tracking and recognizing by smell, and that other animals appear to be similarly endowed, though most usually we cannot perceive the smell at all which they recognize and follow. It appears that nearly all the hairy quadrupeds have distinctive odours, which they and their companions can readily recognize, secreted by certain glands in the skin placed here and there on the body, often on the legs and toes. Some of these odours, like musk and civet, we can perceive, though most have no effect on us. It seems to be an evidence of the absence of any need for man to produce "perfumes" by the action of his own structure that he has a feeble sense of smell and has so little perception of any perfumes or odours peculiar to himself that he has when civilized always made use of odorous substances (perfumes and scents) extracted from other animals and from plants for the purpose, before the days of cleanliness, of masking the unpleasant odours of putrescence pervading his body and clothing. Later, when dirt became less common, he made use of perfumes for the purpose of giving an agreeable whiff to the olfactory organs of his associates.