132 THE HOMOLOGIES OF THE 



covered by the corium and by a sheath of true horny 

 material; those of the prong-horned antelope consist at 

 their bases of bony processes covered by hairy skin, and are 

 covered by horny sheaths in the rest of their extent. They 

 thus combine the characters of the horns of the giraffe and 

 those of the ordinary antelopes, together with the expanded 

 and branched form of the antlers of the deer. Only the 

 horns of the rhinoceros are composed wholly of horny 

 matter, and this is disposed in longitudinal fibres, so that 

 the horns seem rather to consist of coarse bristles com- 

 pactly matted together in the form of a more or less 

 elongated sub-compressed cone.' True horny matter," the 

 writer says, '' is really a modified form of epidermic tissue, 

 and consists of an albuminous principle termed ' Keratin.' 

 It forms not only the horns of the ox tribe, but also the 

 hoofs, claws, or nails of animals generally, the carapace of 

 the tortoise and the armadillo, the scales of the pangolin, 

 the quills of the porcupine and hedgehog, and the feathers 

 of birds," and I would add to this list the baleen plates of 

 the " Kight " whale, which are developed from the skin of 

 the roof of the mouth, and also the whalebone-like hairs 

 of the tail of the elephant. 



It must, I think, strike any reflecting zoologist as 

 remarkable that animals so closely allied as the deer and 

 the antelope should present such apparently diverse forms 

 of horn-structure. I propose in this paper to endeavour in 

 some degree to reconcile these apparent differences, and to 

 see whether they are not rather outside differences than of 

 the essential structure of these organs. 



If we in the first place take note of the life-history of the 

 horns in these two families of the Ungulata,, we shall ob- 

 serve that in the antelopes, as in bullocks, goats, and sheep, 

 the horns grow slowly during the whole life of the animal, 



