July 23, 1903] 



NATURE 



273 



horse in the lips and muzzle, the nostrils and ears, and 

 in the form of the head. 



The wild horse has a coarse, heavy head, with the 

 lower lip (as is often the case in large-headed horses 

 and in Arabs with large hock callosities) projecting 

 beyond the upper. The nostrils in their outline re- 

 semble those of the domestic horse, while the long 

 pointed ears generally project obliquely outwards, as 

 in many heavy horses and in the Melbourne strain of 

 thoroughbreds. Further, in the wild horse the fore- 

 head is convex from above downwards, as well as from 

 side to side — hence Przewalsky's horse is sometimes 

 said to be ram-headed. In the hybrid the muzzle is 

 fine as in Arabs, the lower lip is decidedly shorter 

 than the prominent upper lip, the nostrils are narrow 

 as in the Kiang, and even at birth the forehead was 

 less rounded than is commonly the case in ordinary 

 foals. The ears of the hybrid, though relatively 

 shorter and narrower than in the Kiang, have, as in 

 the Kiang, incurved dark-tinted tips, and they are 

 usually carried erect or slightly inclined towards the 

 middle line. In the wild horse the 

 croup is nearly straight, and the tail is 

 set on high up, as in many desert 

 Arabs. In the hybrid the croup slopes 

 as in the Kiang and in many ponies, 

 with the result that the root of the tail 

 is on a decidedly lower level than the 

 highest part of the hind quarters. 

 Further, in the young wild horses 1 

 have seen the heels (points of the 

 hocks) almost touch each other, as in 

 many Clydesdales, and the hocks are 

 distinctly bent. In the hybrid the 

 hocks are as straight as in well-bred 

 foals, and the heels are kept well apart 

 in walking. 



Another difference of considerable 

 importance is that while the wild 

 horse neighs, the hybrid makes a 

 peculiar barking sound, remotely sug- 

 gestive of the rasping call of the 

 Kiang. 



The dun Mongol pony's hybrid 

 arrived five weeks before its time, and, 

 though perfect in every way, was 

 short-lived. Only in one respect did 

 this hybrid differ from the one already 

 described. In the Exmoor hybrid the 

 hock callosities are entirely absent ; 

 in the Mongol hybrid the right hock 

 callosity is completely wanting, but the 

 left one is represented by a small, 

 slightly hardened patch of skin 

 sparsely covered with short white 

 hair.* In zebra hybrids out of cross-bred mares ihe 

 hock callosities are usually fairly large, while in 

 hybrids out of well-bred (*' Celtic ") pony mares the 

 hock callosities are invariably absent. The Exmoor 

 pony, though not so pure as the Hebridean and other 

 ponies without callosities, has undoubtedly a strong 

 dash of true pony blood ; the Mongol pony is as 

 certainly saturated with what, for want of a better 

 term, may be called cart-horse blood. As I expected, 

 there were no hock callosities present in the Exmoor 

 hybrid. In the Mongol hybrid there was less evidence 

 of hock callosities than I expected. 



From what has been said it follows that a Kiang- 

 horse hybrid differs from Przewalsky's horse (i) in 

 having at the most the merest vestiges of hock 



i The presence of hair in the imperfectly-formed hock callosity of the 

 Mongol hybrid, together with the presence of hair rudiments in the deve- 

 loping hock callosity of the common horse, certainly lends very httle 

 support to the view held by some zoologists that the chestnuts of the horse 

 .-ire vestiges of glands. 



callosities; (2) in not neighing like a horse; (3) ir> 

 having finer limbs and joints and less specialised hoofs %. 

 (4) in the form of the head, in the lips, muzzle, and 

 ears; (5) in the dorsal band; and (6) in the absence, 

 even at birth, of any suggestion of shoulder-stripes- 

 and of bars on the legs. 



While most of the zoologists who hesitated to regard 

 Przewalsky's horse as representing a distinct and 

 primitive type favoured the view that it was a mule, 

 some asserted that it in no way essentially differed 

 from an ordinary horse. The colts brought from 

 Central Asia, they said, were the offspring of escaped 

 Mongol ponies. Others affirmed that they failed Xx> 

 discover any difference between the young wild horses 

 in the London Zoological Gardens and Iceland ponies 

 of a like age. To test the first of these assertions, I, 

 as already mentioned, mated the chestnut Mongol 

 pony with a young Connemara stallion ; to test the 

 second, I purchased last autumn a recently-imported 

 yellow-dun Iceland mare in foal to an Iceland stallion. 

 I As I anticipated, the chestnut Mongol mare produced 



E. Dar^vin-Wilinot. 



I'K;. ;. — I'.xinoDr pony .iiul liur Hylnid foal, (ft. 9 days. 



a foal the image of herself. This foal, it is hardly 

 necessary to say, decidedly differs from the Przewalsky 

 colts recently imported from Central Asia by Mr. 

 Hagenbeck, and it as decidedly differs from the Kiang 

 hybrids described above. 



The Iceland foal, notwithstanding the upright mane 

 and the woolly coat, for a time of a nearly uniform 

 white colour, could never be mistaken for a wild horse, 

 and the older it gets the differences will become 

 accentuated. 



If Przewalsky's horse is neither a Kiang-pony mule 

 nor a feral Mongolian pony, and if, moreover, it is. 

 fertile (and its fertility can hardly be questioned), 1 

 fail to see how we can escape from the conclusion that 

 it is as deserving as, say, the Kiang to be regarded 

 as a distinct species. Granting Przewalsky's horse is 

 a true wild horse, the question arises : In what way, 

 if any, is it related to our domestic horses? It is stilt 

 too soon to answer this question ; but I venture to 

 think that should we, by and by, arrive at the con- 



NO. 1760, VOL. 68] 



