156 THE METHOD OF DARWIN. 



to exist. " Hence," he said, " I was led to care- 

 fully examine the tail-feathers of the several 

 species of Polyplectron in order to discover 

 whether the ocelli in any of them showed any 

 tendency to disappear, and, to my great satis- 

 faction, I was successful." His whole study of 

 these ocelli is remarkable for the ingenuity 

 with which he worked out the consequences of 

 his theory and verified them ; and explained the 

 intricate pattern as a modification and speciali- 

 zation of more general feather-marking. 



Darwin's theory of descent led him to regard 

 species as only more strongly marked varieties. 

 "From looking at species as only strongly 

 marked and well defined varieties, I was led to 

 anticipate that the species of the larger genera 

 in each country would oftener present varieties 

 than the species of the smaller genera." He 

 tested this deduction by an extensive tabulation 

 of plants and Coleoptera; "and it has invariably 

 proved to be the case that a larger proportion 

 of the species on the side of the larger genera 

 presented varieties than on the side of the 

 smaller genera. " 1 



When once he had got hold of natural selec- 

 tion as the cause that had brought about the 

 adaptations in nature, it was an essential part of 



1 Origin of Species, p. 44. 



