ruminants, represented in our day by the oxen, sheep, goats, and antelopes, the bony core or heart of the horn is protected by a sheath of agglutinated hair, which continues to increase by layers during life. This last form of horn is never shed, but persists through the whole of the animal's existence.
Historically, we know that the earliest ruminants, whose remains are preserved for us in Tertiary strata, were quite hornless; and the gradual evolution of horns and antlers, from the simplest to the most complex, has been traced out in full through successive geological ages by Gaudry, Boyd Dawkins, and other biologists. We can follow in detail the origin and rise of each tine and spike from the mere boss or knob on the forehead of the ancestral form to the branching horns of the reindeer, the wapiti, and the Irish elk. The camel, therefore, in its lack of horns represents for us an early undeveloped stage of the ruminant type, when the ruminants had as yet only just diverged from the common ancestors of the horses and pigs. Darwin has shown that horns and other familiar offensive weapons (especially when peculiar to the males alone, as is the case with the antlers of stags) have been developed in the struggle for mates, and are a necessary result of sexual selection. But all such ornaments belong to the higher and later stages of animal life, and are wholly wanting in the unarmed, undecorated, ugly camel. He is, in fact, a ruminant on which the higher types of selection have been little exercised, though, as we shall presently see, his special adaptations for a desert-life have been carried very far in particular directions, and so have enabled him to hold out bravely in his own narrow and restricted field against all more advanced and more highly specialized animals.
The teeth of the camels and of their allies the llamas tell the same tale in a somewhat different fashion. In all the higher ruminants—giraffes, deer, oxen, antelopes, and goats alike—the weapons of offense are the horns or antlers, and the teeth have almost or entirely ceased to be used in fighting. They have also undergone certain profound modifications of shape and arrangement (interesting only to the technical anatomists), which fit them for cropping grass or other low herbage, but get rid to a great extent of their tearing powers. On the other hand, there is one other group of ruminants besides the camels which is destitute of horns—the little group of musk-deer—and in these pretty, small creatures the canine teeth have been developed into long protruding tusks, which thus take the place of horns as offensive weapons, and are used by the males in their single combats for the possession of their mates. But, in the camels and llamas, no special fighting-weapon of any sort exists. When camels fight at all—which is very rarely—they fight merely by simple biting. They