i8 WHAT EVOLUTION IS 



theless covered the ground and may 

 be profitably looked into now, since 

 it still affords the real support on 

 which the doctrine of evolution rests. 

 This body of evidence comes from five 

 important fields in biology : compara- 

 tive anatomy, embryology, the study 

 of fossils, zoogeography, and the 

 nature of rudimentary organs. 



