204 THE METHOD OF DARWIN. 



earth. Both Agassiz's empirical generaliza- 

 tion that the progenitors of the principal plant 

 and animal groups were generalized forms, 

 and the deductive consequences of Darwin's 

 own theory of natural selection would indicate 

 that the highly differentiated forms are forever 

 handicapped. They have a present advantage 

 in having intensified their adaptation to a cer- 

 tain environment; but in the long run they 

 are doomed because they have lost the power 

 of adaptability to new conditions in direct 

 proportion to their present gain. 



It is curious that Darwin had before him, 

 and mentioned in the same sentence, a case of 

 each kind: Dioncea, with its extreme adapta- 

 tions for insect catching, with only a single 

 species in the genus, restricted to a very small 

 locality, on the verge of extinction ; and Drostra, 

 with the same general advantage of catching 

 insects, but with no extreme adaptations, with 

 a vast number of species in the genus, dis- 

 tributed all but everywhere over the earth. It 

 is as great a surprise that he did not see the 

 connection between extreme specialization and 

 extinction on the one hand, and general advan- 

 tage and wide distribution on the other, as he 

 says it was to him that Dioncza is on the verge 

 of extinction. It is clearly inferable from 



