WHAT EVOLUTION IS 2-] 



every hand with series of parts in 

 which the elements are related, as in 

 the examples just described, and it is 

 one of the achievements of the com- 

 parative method that it has thus 

 yielded incomparably rich and signifi- 

 cant material for philosophical bi- 

 ology. By its means anatomy has 

 been lifted from a discipline of dead 

 description to a science rich in prob- 

 lems and resources. 



This advance in method had an 

 immediate and decisive bearing on 

 the evolutionary question. If organ- 

 isms were separately created there 

 would be every reason to expect that 

 they would be constructed upon indi- 

 vidual plans, and not the least ground 

 to anticipate in them an underlying 

 common type of structure. If, how- 

 ever, they have evolved from a 

 common ancestry, precisely such un- 

 derlying similarities might be ex- 



