SEXUAL SELECTION 707 



l&eir enemies, and that they wonld have especially re- 

 quired this protection, as soon as the carnivora increased 

 in size and number during the tertiary periods. This may 

 be .the true explanation, but it is rather strange that the 

 yonng should not have been thus protected, and still more 

 so that the adults of some species should have retained 

 their spots, either partially or completely, during part of 

 the year. We know 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, 

 though we cannot explain the cause. Very few horses, 

 except dun-colored kinds, have stripes on any part of their 

 bodies, yet we have good reason to believe that the aborig- 

 inal 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 illus- 

 trates our ignorance of the laws which regulate the appear- 

 ance 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, with the partial 

 exception of A. tceniopus, which has only the cross shoul- 

 der-stripe and generally some faint bars on the legs; and 

 this species inhabits the almost intermediate region of 

 Upper Egypt and Abyssinia." 



Quadrumana. — Before we conclude, it will be well to 

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



« "The Variation of Animals and Plants under Domestacation," 1868, voL 

 i. pp. 61-64. 



« "Proe. Zoolog. Sec," 1862, p. 164 See, also, Dr. Hartmann, "Ann. 

 d. Landw.," Bd. xliii. s. 222. 



