Chap. XVIII.] ■ QUADRUMANA. 291 



the cause, that when the domestic ass varies and becomes 

 reddish-brown, gray or black, the stripes on the shoulders 

 and even on the spine frequently disappear. Very few 

 horses, except dun-colored kinds, exhibit stripes on any 

 part of their bodies, yet we have good reason ta believe 

 that the aboriginal horse was striped on the legs and spine, 

 and probably on the shoulders. 42 Hence the disappear- 

 ance of the spots and stripes in our adult existing deer, 

 pigs, and tapirs, may be due to a change in the general 

 color of their coats ; but whether this change was effected 

 through sexual or natural selection, or was due to the di- 

 rect action of the conditions of life, or some other unknown 

 cause, it is impossible to deoide. An observation made by 

 Mr. Sclater well illustrates our ignorance of the laws which 

 regulate the appearance and disappearance of stripes; 

 the species of Asinus which inhabit the Asiatic conti- 

 nent are destitute of stripes, not having even the cross 

 shoulder-stripe, while those which inhabit Africa are con- 

 spicuously striped, with the partial exception of A. tmnio- 

 pi(s, which has only the cross shoulder-stripe and generally 

 some faint bars on the legs ; and this species inhabits the al- 

 most intermediate region of Upper Egypt and Abyssinia. 43 



Quadrumana. — Before we conclude, it will be advisa- 

 ble to add a few remarks to those already given on the 

 ornamental characters of monkeys. In most of the spe- 

 cies the sexes resemble each other in color, but in some, 

 as we have seen, the males differ from the females, espe- 

 cially in the color of the naked parts of the skin, in the 

 development of the beard, whiskers, and mane. Many 

 species are colored either in so extraordinary or beautiful 



48 'The Variation of Animals and Plants under Domestication,' 1868, 

 Vol. i. pp. 61-64. 



43 'Proc. Zool. Soc.' 1862, p. 164. See, also, Dr. Hartmann, 'Ann. 

 d. Landw.' Bd. xliii. s. 222. 



