126 UNDKRIIILL : 



locks we have the coalesced second and fourth hoofs should 

 he cleared away by recorded cases of reversion to the three- 

 hoofed type, in which the horn-spurs are entirely absent. 

 Nature is slow to get rid of these vestiges while they do no 

 harm, but, as the hard ground crust or frozen snow of the 

 northern plains would frequently tear the spurs from their 

 attachments, and the consequent bleeding make the wild 

 horses an easier prey to their carnivorous enemies, they 

 should, in the course of adaptive modification, be discarded, 

 and this is exactly what has occurred in the case of the Celtic 

 pony of Iceland, which represents in this and in some other 

 respects the highest degree of specialization yet reached by 

 any member of the Horse family. Though we might natu- 

 rally look upon our modern wild horses, asses and zebras as 

 the nearest to the primitive Equine type, this is only true as 

 to colors and conformation. Here we have the retention of 

 those features most suitable to an environment that is but 

 little changed, while the discarding of the useless remnants of 

 primitive organs has made the greatest progress because there 

 has been no interruption ; natural selection has not given 

 place to artificial selection, and the line remains unbroken. 

 It is among our domestic types, produced by cross-breeding, 

 that we find tapir-like muzzles and the most prominent fetlock 

 spurs and chestnuts ; crossing tends to ativism, and the more 

 the bloods are mixed, the more gross become these ancestral 

 vestiges. 



In any age in which he may be found, the horse, wild or 

 domestic, will possess some characters of a group which pre- 

 dominated in a former age, united with some characters of a 

 group not yet in existence, and with these characters possess 

 those of a group already existing. Thus he clearly demon- 

 strates a principle applicable to the evolution t)f all animal life. 



Thanks to the energies of Professor Henry F. Osborn and 

 his associates in the work. Dr. W. D. Matthew and Mr. J. 

 W. (jidley. there is now availaV)le for study at the American 

 Museum of Natural Histor\- at New York .cit\-, a series of 



