That of the Gardener Bower-bird takes the form of a hut-like structure of twigs, arranged around a central support, commonly a very young sapling. As a rule the thin stems of an orchid (Dendrobium) are used in the construction of this curious hut, whose diameter is about three feet. Before the entrance is a carpet of moss, which is kept clear of leaves or debris of any sort, and on this the most vividly coloured fruit, seed-pods, fungi, and flowers are laid, being constantly replaced as they wither. Newton’s Bower-bird, in like manner, forms a hut around a central column: a hut which may attain to a height of as much as six or even eight feet, and the walls of the pyramid thus raised are generally gaily decorated with flowers and fruit. Around the central a number of subsidiary huts are not infrequently found, and in and out of these the birds pursue one another in ecstasies of excitement.
We have in these facts some extremely puzzling features, which at present, at any rate, permit of no more than a very rough analysis. Probably the whole of these bower-building instincts have their origin in the habit, which the males of so many birds exhibit, of carrying a leaf in the beak when under the excitement of love-making. This is suggestive of nest-building, and in many species this is actually begun before the arrival of a female in the breeding territory, while others build what are known as “cock-nests” which are never used. Among the Bower-birds these “cock-nests” have taken a new and more elaborate form, and are placed on the ground instead of in the trees, the normal site for the nest in all these birds. Furthermore, stages in the evolution of such strange fabrications can be found. These are furnished by the Tooth-billed Bower-bird (Scenopaeetes dentirostris), the Cat-bird (Aeluredus viridus) and the gorgeous Lawe’s Bird of Paradise (Parotid lawesi)—which is not perhaps a Bird of Paradise. These build no bowers, but are content with clearing a patch of ground, of about ten feet in diameter, on which to disport themselves. But while the “displays” of these birds closely resemble one another, in the matter of coloration and ornament they present the most striking contrasts.
CHAPTER VIII
SOME “COLD-BLOODED” LOVERS
The Courtship of the Crocodile—Amorous Lizards—Horned Chamæleons—A flagellating Terrapin—The Frog that would a-wooing go—Semo musical Frogs—Some marvellous instincts in Newts.
The measure of the vitality of animals may be estimated by their response to stimuli; and their behaviour increases in variety and complexity as the nervous system develops. Our interpretation of that behaviour commonly leaves out of account the character of this responsiveness: we are apt to see proof of intelligence in acts which should be read as instinctive. And instinct is to be regarded as a co-ordinated response to stimulus, independent of prior experience.
The complexity of this response stands in very close relation to the structural complexity of the organism in which it occurs, and this because an ever-increasing number of mechanisms and actions must be set in motion to carry out the fulfilment of any given stimulus, as this is traced from the lower to the higher groups of animals: till at last we have to distinguish between movements that are merely reflexes, and those which are “instinctive.” The latter must be fulfilled by the former—the reflex actions are the agents of the instinctive. Indifferent performance in either, endangers the existence of the individual, and in some directions of the race itself.
The sexual instincts, with which alone these pages are concerned, are primarily stimulated and sustained by internal forces, generated, as we have already seen, by the juices of certain glands whose relation to the reproductive system has only recently been discovered. Though not commonly realized, and though denied by some, the sexual instincts are the dominant factors in the animal world. Even Man himself, the lord of Creation, knowing good and evil, cannot escape their overmastering rule. Commonly he is by no means inclined to rebel against this control But there be some who, in their arrogance, imagine that its overthrow is an end to be desired. Having scaled some slight intellectual eminence they fondly imagine this feat was accomplished by virtue of some spiritual grace of their own cultivation, and call to their fellow-men to emulate their example. But such preceptors are labouring under a strange delusion: they are suffering from a disease they wot not of, a “Disharmony,” as Metschnikoff calls it, a disease which blinds their perception of the motive power which has given them all that they believe themselves to have created. For these same despised instincts are the sacred fires of our being, and when they are quenched all that makes us human, love, ambition, and life itself will be extinguished. If the continuance of the race be a thing to be desired it is well that the choice should not be left to us.
Truisms are sometimes trite, and while it is a truism to say that no race can continue which does not reproduce its kind, it is more exact to say that, other things being equal, the race depends for its existence, primarily, on the efficient working of the sexual instincts. In the higher animals, the phenomena which these present are so complex that they often assume something more than a semblance of intelligent, purposeful behaviour. It is therefore necessary, for their right understanding, that they should be analysed in animals lower and lower in the scale of life till at last we come to the very simplest types of organisms wherein instinct can be said to play a part.