NORTHERN ELEPHANT SEAL.
Adult male and female, and yearling. The male shows the enormously inflated snout.
[Face page 88.
That those extraordinary creatures the Cetacea—the Whales and their kin—are derived from the same common stock as the typical carnivora there can nowadays be no doubt, widely as they have departed from their land-dwelling relatives in almost every possible feature of their organization. In the matter of their “Courtship” we know nothing, but we may infer certain incidents in this critical period of their life-history from the peculiar nature of the secondary sexual characters which some species display. Thus in the Pilot Whale (Globicephalus) and the Bottle-nose Whale (Hyperoödon) the forehead, in the bulls, is enormously swollen by a mass of fibrous tissue so dense as to turn the blade of the sharpest knife, as I know well from attempts to dissect this region. Now the only use, surely, for such a cushion is that of a battering-ram by rival males in charging one another, as rams and other horned animals will do. In the Bottle-nose Whale this cushion is backed up by an enormous mass of solid bone thrown up by the maxillæ. The origin of this bony growth is interesting, for it appears first as a slight swelling in the rare species Berardius; it is seen at a further stage of growth in the female “Bottle-nose” (Hyperoödon), and attains its maximum in the male, where it stands unique. There are two other species which demand notice here. The first is Layard’s Beaked Whale (Mesoplodon); the second the Narwhal. The former is the only vertebrate which in a wild state wears a muzzle! In this species the teeth have totally vanished save for a pair in the lower jaw, which are found towards the end of the jaw. These in the adult, or perhaps we should say senile, male grow upwards and inwards, finally meeting one another above the upper jaw, so as to make it impossible for the animal to open its mouth more than the fraction of an inch! Surely here we have a secondary sexual character carried to an excess, and so proving not only disadvantageous to the animal, but positively disastrous, for it seems clear that so hampered the creature can feed only on the most minute forms of animal life, which could only be captured and swallowed with difficulty. It is true that the Rorquals feed on excessively minute Crustacea, but they are able to take in enormous quantities at a time, the “whalebone” serving the office of a sieve to prevent their escape. The Mesoplodon has no such aids. One is tempted to believe that the skulls displaying this most curious feature are abnormal, comparable to those, say, of rabbits wherein the teeth have grown so excessively long as to close the mouth, on account of the displacement of the cutting surfaces by accident. But there is nothing to afford support to this view, and one must therefore fall back on the suggestion of senility.
The Narwhal has long been celebrated for the enormous size of the canine teeth, the only teeth present in the jaws. As a rule, only one leaves its bony socket, the other, commonly the right, remaining as a mere vestige, seven or eight inches long within the skull. The protruding tooth, which is spirally fluted, may attain a length of nine feet. Occasionally both teeth are developed, and in this case the spiral is the same, differing in a very striking manner from the spiral horns of ruminants, wherein one presents a right, the other left-handed spiral. But what purpose do these teeth serve? This question has never yet been definitely settled. Some hold that it is used to break open breathing holes in the ice, for the animal lives in the far north: others that it is used as a spear in hunting prey. Some aver that it serves as a weapon of offence, being used by rival males in their struggle for mates. Scoresby, the explorer, indeed, says he has seen young males in mock-battle, fencing with these remarkable weapons. But until we have more satisfactory data, we must regard this armature of the Narwhal as affording another instance of a secondary sexual character of doubtful value to its possessor.
CHAPTER VI
COURTSHIP AMONG BIRDS
Generalities—Darwin v. Wallace—The Peacock in his Pride—The “Display” of the Peacock Pheasant—The Splendour of the Argus Pheasant and the Marvel of its Eyes—The Frill of the Amherst Pheasant—Birds of Paradise in the Toils of Love—Inflated Suitors—Ruffs and Reeves—Fearsome Weapons and their Uses—Birds which dance—Musical Birds—The Bird’s Voice-box—The “Lek” of the Capercaillie—Instruments of Percussion—The Curious Performance of the Wood-pecker.
The fact that so little is known about the mammals during that period when the all-important work of securing mates is going on, and of the subsequent events, is largely due to the difficulties which close observation of this phase of their life-history entails. With the birds matters are far otherwise; their haunts are more accessible; they are far more numerous, and much more easily kept under observation. Consequently, we have a tolerably complete knowledge of the lives of some species, at any rate, during the reproductive period; that is to say, as to the sequence of events from the beginning of the reproductive activities onwards; but the interpretation of what is seen is another matter. No attempt which has yet been made to fathom the psychology of sex has yielded more than a slight insight into what is taking place. Nevertheless, this is an aspect of the subject which has a far more important bearing on the problems of evolution than is generally realized. But these pages are concerned rather with the relations between the sexes, than with the subtle forces which have fashioned and control conduct in this regard.