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.