134 PERIOD V. 



to suppose that the eye, with all its inimitable 

 adjustments, had been formed by an unconscious natural 

 process seemed to him absurd until he had traced a 

 good many intermediate steps between the mere colour- 

 spot and the eye of the eagle. He writes to Asa Gray 

 (September 5, 1857) that the facts which had done most 

 to keep him scientifically orthodox were facts of adapta- 

 tion, the pollen-masses of Asclepias, the mistletoe with 

 its pollen carried by insects and its seeds by birds, the 

 woodpecker exquisitely fitted by feet, tail, beak, and 

 tongue to climb trees and capture insects. 



The student of adaptations has no longer a moral 

 thesis to maintain ; he tries to understand how a con- 

 trivance acts, what advantage it confers upon its 

 possessor, and by what steps it was perfected. The 

 minute variations of species are as capricious as the 

 form of the stones which accumulate at the foot of a 

 precipice ; natural selection turns fortuitous variations 

 to account for the advantage of the species as a builder 

 might turn to account the shapes of the stones. Man 

 himself can employ variations for frivolous or even base 

 purposes, as when he produces toy-spaniels or bull- 

 dogs. 1 The adjustments of organic structures often 

 move our wonder by their perfection. One reason why 

 they so far exceed the adjustments made by wind, frost, 

 or moving water is that the process has been so pro- 

 tracted ; in a worm or an insect we see the last stage 

 of an adaptation which has been continuously at work 

 for untold geological periods. Another reason is that 

 the thing adapted is alive, sensitive, and capable of 

 responding to the subtlest imaginable influences. . 



Darwinism and Non-biological Studies. The theory 



1 Darwin, Variation of Plants and Animals under Domestica- 

 tion, Concluding" Remarks. 



