RUDIMENTARY ORGANS. 95 



World horses and their history, and gives them an antiquity 

 compared with which the events of man's primitive history in either 

 world are but as yesterday. Recent researches amongst the rock 

 formations of Western America, in particular, have shown us that it 

 is to the New World we must look for a perfect pedigree of the horse. 

 For, beginning with the horse of to-day with its splint-bones, we are 

 carried gradually backwards in time to the Pliocene horse of the New 

 World named Pliohippus (B, B I ) a form not differing materially from 

 the living horse, but serving in a very gradual fashion to introduce 

 us to the older Protohippus, the New World representative of our own 

 fossil Hipparion (c, c 1 ), and in some respects a more typical three- 

 toed horse than the latter. Our own Anchitherium (D, D 1 ) corre- 

 sponds to the next specimen of the New World Miohippus by 

 name ; and Miohippus evinces a still more important modification 

 in that it possesses a rudiment of the fifth or little finger (D, e) 

 in addition to the second, third, and fourth digits with which the 

 fore-feet are provided. 



The American horses now continue the history of the race in 

 time past without aid or representative from the Eastern Hemisphere, 

 in so far, at least, as the latest research has shown. To Miohippus 

 succeeds the Mesohippus (E, E I ) from the American Miocene, which 

 has three well-developed toes, and in addition shows the rudiment of 

 the little finger (E, e) of the fore-feet (seen also in Miohippus, D, e) in 

 an enlarged condition. Passing to the Eocene formations, the oldest 

 series of the Tertiary rocks, we meet with the next step in the form 

 of the Orohippus (F, F 1 ), in which the little finger (e) appears as a 

 veritable member of the hand, the hind feet still possessing three 

 well-developed toes only: whilst, consistently with the development 

 of the toes, the ulna of the fore-arm and fibula of the leg appear as 

 bones of legitimate size, and present a striking contrast to their 

 rudiments in the horse of to-day. The last discovered horse is from 

 the oldest of the Eocene beds ; it has been appropriately named 

 Eohippus, and presents us with four complete fingers (second, third, 

 fourth, and fifth) on the fore-feet, and a rudiment of the first finger as 

 well ; with a trace of the fifth toe of the hind feet this last member 

 being, as we have seen, unrepresented in any of the other forms. 

 When the Chalk rocks shall have yielded up their fossil horses, it is 

 consistent with logic and reason to expect that the primitive stock of 

 the horses will be discovered with its complete provision of five toes, 

 and its corresponding modifications of form. 



To what conclusions, of reasonable kind, do these stable facts 

 regarding the pedigree of the horse naturally lead ? The answer is to- 

 wards a belief in the slow and progressive modification and evolution 

 of the one-toed modern horse from a five-toed ancestor. This process 

 of modification must, of course, have affected its entire frame, but it 



