Chap. XVIII.] QUADRUMANA. 295 



cus frontatus likewise has a blackish face with a long 

 black beard, and a lai'ge naked spot on the forehead of a 

 bluish-white color. The face of Macacus lasiotus is dirty 

 flesh-colored, with a defined red spot on each cheek. The 

 appearance of Cercocehus ^thiops 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 difierent color from the rest of the head, 

 and, when different, are always of a lighter tint,^* beiug 

 often pure white, sometimes bright yellow, or reddish. 

 The whole face of the South- American Srachyurus 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 wonderfully in color in the various 

 species. It is often brown or flesh-color, with parts per- 

 fectly 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 

 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 Rhesus, in which 

 the face and the posterior parts of the body are brilliantly 

 colored in one sex alone. In these latter cases we have 

 every reason to believe that the colors were acquired 

 through sexual selection ; and we ai'e naturally led to 

 extend the same view to the foregoing species, though 



** I observed this fact in the Zoological Gardens ; and numerous 

 cases may be seen in the colored plates in GeofFroy St.-Hilaire and F, 

 Cuvier, 'Hist. Nat. des Mammiferes,' torn. i. 1824. 



** Bates, ' The Naturalist on the Amazons,' 1863, vol. ii. p. 310. 



