ORGANIC EVOLUTION 357 
of which the record is fairly well preserved. Moreover, the 
records show that the atavus of the horse began in North 
America, and that by migration the primitive horses spread 
from this continent to Europe, Asia, and Africa. 
So far we have treated the question of fixity of species as 
a historical one, and have gone searching for clues of past 
Fic. 106.—Bones of the Foreleg and Molar Teeth of Fossil Ancestors 
of the Horse. European Forms. (After Kayser.) 
conditions just as an archeologist explores the past in buried 
cities. The facts we have encountered, taken in connection 
with a multitude of others pointing in the same direction, 
begin to answer the initial question, Were the immense num- 
bers of living forms created just as we find them, or were 
they evolved by a process of transformation ? 
