While we cannot suppose these animals to possess any standard of beauty or ugliness, it must not be forgotten that they are more or less conscious, not only of the existence of these brightly-coloured areas, but of the effect they produce, as Darwin showed long since in the cases of a captive Mandrill, and some other smaller species of Monkeys, among them a Rhesus Monkey. These, when shown a looking-glass, at once presented their hinder ends to what they supposed to be the new arrival. A similar mark of friendliness was shown towards their keeper, and visitors introduced by him. Periodically, under the sexual stimulus, this desire becomes intensified and becomes an invitation to mating. In this connection it is interesting to note that in some of the Macaque Monkeys we have signs of a reversal of the usual sequence of coloration. For in the Pigtailed Macaque the young of both sexes are more brilliantly coloured than the adults, in regard to the bare skin areas, while in the Hairy-eared Macaque (_M. lasiotis_) and the Rhesus Monkey (_M. rhesus_) the face of the female is brighter than that of the male. This surely means that this coloration is in process of suppression, for according to the rule the male is the first to develop new characters, then the female, and finally they are transmitted to the young. The extra brightness in the young, then, is to be regarded not as an incipient, but as an ancestral character in process of elimination. As a rule, among the Mammals at any rate, brilliant coloration and weapons of offence are not associated in the same animal. The Baboons, and the Mandrill in particular, are exceptions, for these animals are provided with most formidable “tusks,” the canines of both upper and lower jaws being of great size, and opposed one to another in such a way that they wear away to form sharp, angular cutting-edges, more murderous than the fangs of the Tiger.