542 THE DESCENT OP MAN. 



What resembled the Hyomoschus aquaticus — for this animal is 

 spotted, and the hornless males have large exserted canine teeth, 

 of which some few true deer still retain rudiments. Hyomoschus, 

 also, offers one of those interesting cases of a form linking to- 

 gether two groups, for it is intermediate in certain osteological 

 characters between the pachyderms and ruminants, which were 

 formerly thought to be quite distinct.*^ 



A curious difficulty here arises. If we admit that colored spots 

 and stripes were first acquired as ornaments, how comes it that 

 so many existing deer, the descendants of an aboriginally spotted 

 animal, and all the species of pigs and tapirs, the descendants of 

 an aboriginally striped animal, have lost in their adult state their 

 former ornaments? I cannot satisfactorily answer this question. 

 We may feel almost sure that the spots and stripes disappeared 

 at or near maturity in the progenitors of our existing species, so 

 that they were still retained by the young; and, owing to the law 

 of inheritance at corresponding ages, were transmitted to the 

 young of all succeeding generations. It may have been a great 

 advantage to the lion and puma, from the open nature of their 

 usual haunts, to have lost their stripes, and to have been thus 

 rendered less conspicuous to their prey; and If the successive 

 variations, by which this end was gained, occurred rather late in 

 life, the young would have retained their stripes, as is now the 

 case. As to deer, pigs, and tapirs, Fritz Mtiller has suggested 

 to me that these animals, by the removal of their spots or stripes 

 through natural selection, would have been less easily seen by 

 their enemies; and that they would have especially required 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 young 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 aboriginal horse was striped on the 

 legs and spine, and probably on the shoulders.'^ Hence the dis- 

 appearance 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 



*2 Falconer and Cautley, 'Proc. Geolog. Soc' 1843; and Falconer's 

 'Pal. Memoirs,' vol. i. p. 196. 



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

 vol. 1. p. 61-64. 



