543 



The Descent of Alan. 



Part II, 



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



IL 





FIfr. ?z. Head of Semnopithecus rubicundus. This and the following figures (from 

 Prof. Gervais) are given to shew the odd arrangement and development of the hail 

 on the head. 



the cross shoulder-stripe, whilst those which inhabit Africa are 

 conspicuously striped, with the partial exception of A. t&niopus, 

 which has only the cross shoulder- stripe and generally some 

 faint bars on the legs ; and this species inhabits the almost inter- 

 mediate region of Upper Egypt and Abyssinia. 44 



44 ' Proc. Zool. Soc' 1862, p. 164. Landw.' Bd. xliii. s. 222. 

 See, also, Dr. Hartmann, 'Ann. d. 



