626 TEE DESCENT OF MAN. 



retained their spots, cither partially or completely, during 

 part of the year. We know that when the domestic ass 

 varies and be'comes reddish-brown, gray or black the stripes 

 on the shoulders and even on the spine frequently disap- 

 pear, though we cannot explain the cause. Very few 

 norses, except dun-colored kinds, have stripes on any part 

 of their bodies, yet we have good reason to believe that the 

 aboriginal horse was striped on the legs and spine, and 

 probably on the shoulders.* Hence the disappearance 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 direct action of the 

 conditions of life, or to some other unknown cause, it is 

 impossible to decide. 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 continent are destitute of 

 stripes, not having even the cross shoulder-stripe, while 

 those which inhabit Africa are conspicuously striped, \vith 

 the partial exception of A. tceniopus, which has only the 

 cross shoulder-stripe and generally some faint bars on the 

 legs; and this species inhabits the almost intermediate 

 region of Upper Egypt and Abyssinia. \ 



. Before we conclude, it will be well to 

 add a few remarks on the ornaments of monkeys. In most 

 of the species the sexes resemble each other in color, but in 

 some, as we have seen, the males differ from the females, 

 especially 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 so beautiful 

 a manner, and are turnished with such curious and elegant 

 crests of hair, that \ve can hardly avoid looking at these 

 characters as having been gained for the sake of ornament. 

 The accompanying figures (72 to ?G) serve to show 

 the arrangement of the hair on the face and head in sev- 

 eral species. It is scarcely conceivable that these crests of 



*"The Variation of Animal.? and Plants under Domestication," 

 1868, vol, i, pp. 61-64. 



f "Proc. Zool. Soc.," 1S62. p. 1<U, See also, Dr. Hartman, "Ann. 

 d, Landw.," 13d. xiiii, s. 222. 



