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Show 312 f-JEX.UAL SELECTION: 1\IAMl\IALS. PAilTH. arc orange-coloured, with tho upper partblaclc, forming a band which extends backwards to the ears, the latter being clothed with whitish hairs. In the Zoological Society's Gardens I have . often overheard visitors a<lmiring the beauty of another monkey, deservedly called Cercopithecus Diana (fig. 76) ; the general colour of the fur is grey; the chest and inner surface of the fore-legs arc w bite ; a large triangular defined space on the hinder part of the back is rich chesnut; in the male the inner sides of the thighs and the abdomen are delicate fawncolonred, and the top of the head is black ; the face and ears are intensely black, finely contrasted with a white transverse crest OYOt' the eye-brows and with a long white peaked beard, of which the basal portion is black.t6 In these and many other monkeys, the beauty and singular arrangement of their colours, and stilt more the diversified am] elegant arrangement of the crests and tufts of hair on their heads, force the conviction on my mind that these characters have been acquired through sexual selection exclusively as ornaments. Summary.-The law of battle for the possession of the female appears to prevail throughout the whole great class of mammals. Most naturalists will admit that the greater size, strength, courage, and pugnacity of the male, his speeial weapons of offence, as well as his special means of defence, have all been acquired or modified through that form of selection which I have 46 I hnve seen mo t of the rtbovc-narnod monkeys in the Zoological Ho<'ivt,v'~:~ Gar<1cm. 'l'he description of the Semnopilhecus nemw11s il:! tak n from l\Tr. W. 0.1\fartin's 'Nat. Ilist. of Mammalia,' 18-11, p. 'LGO; sec abo p. 475, 5:lil. •CuAP. XVJII. 1-;Ul\Il\IARY. 313 called sexual selection. This does not depend on any superiority in the general struggle for life, but on .certain individuals of one sex, generally the male sex, having been successful in conquering other males, and on their having left a larger number of offspring to inherit their superiority, than the less successful males. There is another and more peaceful kind of contest, in which the males endeavour to exeite or allure the females by various charms. This may be effected by the powerful odours emitted by the males during the breeding-season; the odoriferous glands having been .acquired through sexual selection. vYhether the same view can be extended to the voice is doubtful, for the vocal organs of the males may have been strengthened by use during maturity, under the powerful excitements .of love, jealousy, or rage, and transmitted to the same sox. Various crests, tufts, and mantles of hair, which are either confined to the malo, or are more develop (l in this sox thnn in the females, seem iu most cases to be merely ornamental, though they sometimes serve as a defence against rival males. There is even reason to suspect that tho branching homs of stags, and the elegant horns of certain antelopes, though properly serving as weapons of offence or of defence, have been partly modified for the sake of ornament. When the male differs in colour from the female he generally exhibits darker and :more strongly-c-ontrasted tints. We do not in this class meet with the splendid 1·ed, blue, yellow, and green colours, so common with male birds and many other animals. The naked parts, however, of certain Quadrumana must be excepted; for surh parts, olton oddly situated, are coloured in some species in the most brilliant manner. The colours of .the male in other cases may be duo to simple variation, |