EVIDENCES OF EVOLUTION 43 



in discharging the same function, they arc 

 said to be analogous. This distinction of the 

 two kinds of likeness, which are confused in 

 popular thought and language, is of far-reach- 

 ing importance. The discipline of compara- 

 tive anatomy, largely by help of the Platonic 

 idea of the "archetype" the essential or 

 ideal form of each group or species had made 

 the idea of homology clear before it reached 

 its evolutionist interpretation ; and research 

 increasingly showed that if classification ia 

 to be a grouping together of forms that are 

 deeply alike, it must rest on a recognition 

 of homologies, and that a grouping according 

 to analogical resemblances is bound to be 

 fallacious. 



Aristotle (384-322 B.C.) recognized real 

 kinship when he ranked whales with mammals, 

 not with fishes; and bats with mammals, not 

 with birds. And from that early date till 

 now the successful classifiers of animals or 

 of plants have been those who saw clearly 

 through all deceptive suggestions of functional 

 resemblance (analogy), and got down to the 

 sure foundation of structural and develop- 

 mental resemblance (homology). 



To make the distinction between homologies 

 of essential form and mere analogies of use 

 more concrete, let us recall the three instances 



