SEXUAL SELECTION 711 



appearance of Cercocebus cetMops is grotesque, with its black 

 face, white whiskers and collar, chestnut 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 color 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 color does not appear until the animal 

 is nearly mature." The naked skin of the face differs won- 

 derfully in color in the various species. It is often brown 

 or flesh-color, with parts perfectly white, and often as black 

 as that of the most sooty negro. In the Brachyurus the scar- 

 let 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 gray. In all the species known to Mr. Bartlett, in 

 which the adults of both sexes have strongly colored faces, 

 the colors are dull or absent during early youth. This like- 

 wise holds good with the mandrill and Ehesus, in which the 

 face and the posterior parts of the body are brilliantly col- 

 ored in one sex alone. In these latter cases we have reason 

 to believe that the colors were acquired through sexual se- 

 lection; and we are naturally led to extend the same view 

 to the foregoing species, though both sexes when adult have 

 their faces colored in the same manner. 



Although many kinds of monkeys are far from beautiful 

 according to our taste, other species are universally admired 

 for their elegant appearance and bright colors. The Semno- 

 pithecus nemceus, though peculiarly colored, is described as 

 extremely pretty; the orange-tinted face is surrounded by 

 long whiskers of glossy whiteness, with a line of chestnut 

 red over the eyebrows; the fur on the back is of a delicate 



" I observed this fact in the Zoological Society's Gardens; and many cases 

 may be seen In the colored plates in GeofEroy St. Hilaire and F. Cuvier, "Hi»- 

 toire Naturel des Mammif^res," torn, i., 1824. 



<« Bates, "The Naturalist on the Amazons," 1863, vol. ii. p. 310. 



