The Metaphysics of Darwinism. 79 



have just said, constitute the material for natural 

 selection. In the earlier editions of the &quot; Origin 

 of Species &quot; much influence was ascribed to the 

 external conditions of life, which Geoffrey Saint 

 Hilaire, a generation before, had declared the 

 principal cause of change. But apart from the 

 environment, Darwin always maintained, with 

 Lamarck, that habit, or use and disuse, played a 

 considerable part in the modification of the con 

 stitution and structure. Thus if, as is the case, 

 the bones of the wing of the domestic duck weigh 

 less and the bones of the leg more, in proportion 

 to the whole skeleton, than do the same bones in 

 the wild duck, the change may be safely attrib 

 uted, he tells us, to the domestic duck flying 

 much less and walking more than its wild par 

 ents. Lastly, there are modifications which emerge 

 as concomitants or indirect effects of other modifi 

 cations. The whole organism is so conjoined and 

 knitted together during its growth and develop 

 ment, that when slight variations occur and are 

 accumulated in one part, other parts become modi 

 fied, too. A curious instance of this correlated 

 variation, not in process, but in complete realiza 

 tion, is presented by the uniform conjunction of 

 deafness with blue eyes in perfectly white cats. 

 But however much be ascribed to the influence 



