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 
