and it is inconceivable that they can be of use in any ordinary way to these animals. If so, they have probably been gained through sexual selection, though transmitted equally, or almost equally, to both sexes. With many of the Quadrumana, we have additional evidence of the action of sexual selection in the greater size and strength of the males, and in the greater development of their canine teeth, in comparison with the females. 45 A few instances will suffice of the strange manner in which both sexes of some species are coloured, and of the beauty of others. The face of the Cercopithecus petaurista (fig. 77) is black, the whiskers and beard being white, with a defined, round, white spot on the nose, covered with short white hair, which gives to the animal an almost ludicrous aspect. The Semnopithecus frontatus likewise has a blackish face with a long black beard, and a large naked spot on the forehead of a bluish-white colour. The face of Macacus lasiotus is dirty flesh-coloured, with a defined red spot on each cheek. The appearance of Cercocebus æthiops is grotesque, with its black face, white whiskers and collar, chesnut head, and a large naked white spot over each eyelid. In very many species, the beard, whiskers, and crests of hair round the face are of a different colour from the rest of the head, and when different, are always of a lighter tint, being often pure white, sometimes bright yellow, or reddish. The whole face of the South American Brachyurus calvus is of a "glowing scarlet hue;" but this colour does not appear until the animal is nearly mature.46 The naked skin of the face differs wonderfully in colour in the various species. It is often brown or flesh-colour, with parts perfectly white, and often as black as that of the most sooty negro. In the Brachyurus the scarlet tint is brighter than that of the most blushing Caucasian damsel. It is sometimes more distinctly orange than in any Mongolian, and in several species it is blue, passing into violet or grey. In all the species known to Mr. Bartlett, in which the adults of both sexes have strongly-coloured faces, the colours are dull or absent during early youth. This likewise holds good with the mandrill and Rhesus, in which the face and the posterior parts of the body are brilliantly coloured in one sex alone. In these latter cases we have reason to believe that the colours were acquired through sexual selection; and we are naturally led to extend the same view to the foregoing species, though both sexes when adult have their faces coloured in the same manner. 45 I observed this fact in the Zoological Gardens; and many cases may be seen in the coloured plates in Geoffroy St.-Hilaire and F. Cuvier, 'Hist. Nat. des Mammifères,' tom. i. 1824. 46 Bates, "The Naturalist on the Amazons,' 1863, vol. ii. p. 310. Although many kinds of monkeys are far from beautiful according to our taste, other species are universally admired for their elegant appearance and bright colours. The Semnopithecus nemæus, though peculiarly coloured, is described as extremely and it is inconceivable that they can be of use in any ordinary way to these animals. If so, they have probably been gained through sexual selection, though transmitted equally, or almost equally, to both sexes. With many of the Quadrumana, we have additional evidence of the action of sexual selection in the greater size and strength of the males, and in the greater development of their canine teeth, in comparison with the females. A few instances will suffice of the strange manner in which both sexes of some species are coloured, and of the beauty of others. The face of the Cercopithecus petaurista (fig. 77) is black, the whiskers and beard being white, with a defined, round, white spot on the nose, covered with short white hair, which gives to the animal an almost ludicrous aspect. The Semnopithecus frontatus likewise has a blackish face with a long black beard, and a large naked spot on the forehead of a bluish-white colour. The face of Macacus lasiotus is dirty flesh-coloured, with a defined red spot on each cheek. The appearance of Cercocebus æthiops is grotesque, with its black face, white whiskers and collar, chesnut head, and a large naked white spot over each eyelid. In very many species, the beard, whiskers, and crests of hair round the face are of a different colour from the rest of the head, and when different, are always of a lighter tint, being often pure white, sometimes bright yellow, or reddish. The whole face of the South American Brachyurus calvus is of a "glowing scarlet hue;" but this colour does not appear until the animal is nearly mature.46 The naked skin of the face differs wonderfully in colour in the various species. It is often brown or flesh-colour, with parts perfectly white, and often as black as that of the most sooty negro. In the Brachyurus the scarlet tint is brighter than that of the most blushing Caucasian damsel. It is sometimes more distinctly orange than in any Mongolian, and in several species it is blue, passing into violet or grey. In all the species known to Mr. Bartlett, in which the adults of both sexes have strongly-coloured faces, the colours are dull or absent during early youth. This likewise holds good with the mandrill and Rhesus, in which the face and the posterior parts of the body are brilliantly coloured in one sex alone. In these latter cases we have reason to believe that the colours were acquired through sexual selection; and we are naturally led to extend the same view to the foregoing species, though both sexes when adult have their faces coloured in the same manner. 43 I observed this fact in the Zoological Gardens; and many cases may be seen in the coloured plates in Geoffroy St.-Hilaire and F. Cuvier, • Hist. Nat. des Mammifères,' tom. i. 1824. 46 Bates, "The Naturalist on the Amazons,' 1863, vol. ii. p. 310. Although many kinds of monkeys are far from beautiful according to our taste, other species are universally admired for their elegant appearance and bright colours. The Semnopithecus nemæus, though peculiarly coloured, is described as extremely pretty; the orange-tinted face is surrounded by long whiskers of glossy whiteness, with a line of chesnut-red over the eyebrows; the fur on the back is of a delicate grey, with a square patch on the loins, the tail and the fore-arms being of a pure white; a gorget of chesnut surmounts the chest; the thighs are black, with the legs chesnut-red. I will mention only two other monkeys for their beauty; and I have selected these as presenting slight sexual differences in colour, which renders it in some degree probable that both sexes owe their elegant appearance to sexual selection. In the moustache-monkey (Cercopithecus cephus) the general colour of the fur is mottledgreenish with the throat white; in the male the end of the tail is chesnut, but the face is the most ornamented part, the skin being chiefly bluish-grey, shading into a blackish tint beneath the eyes, with the upper lip of a delicate blue, clothed on the lower edge with a thin black moustache; the whiskers are orange-coloured, with the upper part black, 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 admiring the beauty of another monkey, deservedly called Cercopithecus diana (fig. 78); the general colour of the fur is grey; the chest and inner surface of the forelegs are white; 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 fawn-coloured, and the top of the head is black; the face and ears are intensely black, contrasting finely with a white transverse crest over the eye-brows and a long white peaked beard, of which the basal portion is black.47 In these and many other monkeys, the beauty and singular arrangement of their colours, and still more the diversified and 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 special weapons of offence, as well as his special means of defence, have been 47 I have seen most of the above monkeys in the Zoological Society's Gardens. The description of the Semnopithecus nemæus is taken from Mr. W. C. Martin's 'Nat. Hist. of Mammalia,' 1841, p. 460; see also pp. 475, 523. |