Normally sluggish, the Lizards display, it will have been remarked, a quite surprising degree of animation when maddened by mate-hunger. Some exhibit a considerable degree of pugnacity. In _Anolis carolinensis_, for example, when two males meet they face one another, bob the head up and down two or three times, expand the throat pouch, lash their tails from side to side, and then, worked up to the requisite degree of fury, rush at one another, rolling over and over and holding firmly with the teeth. The conflict generally ends in one of the combatants losing his tail, which is eaten by the victor. The Chamæleons include among their number species which have developed quite formidable horns, recalling those of the Rhinoceros or, better, of the extinct Arsinoetherium, since they are placed side by side instead of one behind the other. In Owen’s Chamæleon there are three such horns, two on the forehead and a median horn on the snout, and these are borne only by the males. The marvellous play of colour which many Lizards display is commonly attributed indifferently to “protective coloration” and to “sexual selection.” It is unlikely that both have played equally important parts in their development. If the case of certain of the Geckoes alone is taken, then there would seem to be no doubt but that “Natural Selection” was the agent which had determined their elaborations for protective purposes, and in such and similar cases this may be largely true. But the material which “Natural Selection” has worked upon has been furnished by the secretions of the sexual glands to which reference has so frequently been made already. These seem to possess a very marked tendency to contain an excitant which promotes the formation of intense pigmentation, or an excess of tissue which may assume the form of weapons of offence, or of excrescences in the form of spines, or other ornamental features. Animals in whom this tendency to pigmentation and ornament has developed must, so to speak, obtain a licence from “Natural Selection” if they are to retain it. That is to say, if such ornament whenever it appears makes the wearer conspicuous to its enemies, or hampers it in escaping therefrom, or in fulfilling the ordinary avocations of life, then its further progress will be inhibited, or the wearer will be exterminated. But the tendency to produce colour, a by-product of the sexual gland secretions, may incidentally serve to afford it a protective garb, and in this event its further elaboration in the required direction is assured.