382 UNGULATA 



when reintroduced by man, form curious but as yet unsolved 



problems in geographical distribution. 



Existing Species. — The existing species of the genus are the 

 following : — 



The Horse, Equus caballus, is distinguished from the others by 

 the long hairs of the tail being more abundant and growing quite 

 from the base as well as the end and sides, and also by possessing 

 a small bare callosity on the inner side of the hind leg, just below 

 the " hock " or heel joint, in addition to the one on the inner side 

 of the fore limb above the carpus, common to all the genus. The 

 mane is also longer and more flowing, and the ears are shorter, 

 the limbs longer, the hoofs broader, and the head smaller. 



Though the existing Horses are not usually marked in any 

 definite manner, or only irregularly dappled, or spotted with light 

 surrounded by a darker ring, many examples are met with showing 

 a dark median dorsal streak like that found in all the other 

 members of the genus, and even with dark stripes on the shoulders 

 and legs indicating "the probability of the descent of all the 

 existing races from a single dun-coloured, more or less striped, 

 primitive stock, to which our horses still occasionally revert." : 



In Europe wild Horses were extremely abundant in the 

 Xeolithic or polished-stone period. Judging from the quantity of 

 their remains found associated with those of the men of that time, 

 the chase of these animals must have been among man's chief 

 occupations, and they must have furnished him with one of his 

 most important food supplies. The characters of the bones 

 preserved, and certain rude but graphic representations carved on 

 bones or reindeers' antlers, enable us to know that these Horses 

 were rather small in size, and heavy in build, with large heads and 

 rough shaggy manes and tails, much like, in fact, the present wild 

 horses of the steppes of the south of Russia. They were 

 domesticated by the inhabitants of Europe before the dawn of 

 history, but it is doubtful whether the majority of the animals now 

 existing on the Continent are derived directly from them, as it is 

 more probable that they are descendants from Horses imported 

 through Greece and Italy from Asia, derived from a still earlier 

 domestication, followed by gradual improvement through long- 

 continued attention bestowed on their breeding and training. 

 Horses are now diffused by the agency of man throughout almost 

 the whole of the inhabited parts of the globe, and the great modifica- 

 tions they have undergone in consequence of domestication and 

 selective breeding are well exemplified by comparing such extreme 

 forms as the Shetland pony, dwarfed by uncongenial climate, the 

 thoroughbred racer, and the London dray-horse. In Australia, 



1 Darwin, Variation of Animals and Plants under Domestication, 1868, vol. 

 i. chap. ii. 





