226 THE MEANING OF EVOLUTION 



has but three toes, while the front still has four. This 

 is not the only advance. Already the middle toe of 

 the original set of five is becoming emphasized. The 

 weight is thrown more forcibly upon it, as with the 

 human foot it is upon the inner or big toe. The mid- 

 dle toe is growing larger and larger, and the nail 

 upon it is spreading around it and is growing firmer. 

 The creature, too, is standing more nearly upon his 

 toes; his legs are getting longer; he stands higher 

 from the ground, and now has come to be the size of 

 a hound. 



We can only surmise why this creature should have 

 undergone such a change, but the presence of flesh- 

 eating animals having the size of a fox, and pre- 

 sumably of the fox's swiftness, probably tells the 

 story. The little bands of early horses, pursued by 

 their carnivorous foes, were slowly modified into 

 swifter creatures. It is not so much that running 

 made them fast, as that the slow ones were contin- 

 ually being caught. If this process of constant elimi- 

 nation of the slow members of any herd is kept up 

 long enough, the group will necessarily develop speed. 

 As time goes on, of these early horses those which 

 happened to have longer legs and stood higher upon 

 their toes won in the race, and handed on their quali- 

 ties to their long-legged descendants. As the animal 

 rose upon his toes, the inner toe, corresponding to our 



