146 EVOLUTION 



conclusion, even if well founded, would be 

 unsatisfactory unless it could be shown how 

 the innumerable species inhabiting this world 

 have been modified so as to acquire that per- 

 fection of structure and co-adaptation which 

 justly excites our admiration." Again, "It 

 is therefore of the highest importance to 

 gain a clear insight into the means of modi- 

 fication and co-adaptation. At the com- 

 mencement of my observations it seemed to 

 me probable that a careful study of domesti- 

 cated animals and cultivated plants would 

 offer the best chance of making out this 

 obscure problem. Nor have I been disap- 

 pointed: in this and in all other perplex- 

 ing cases I have invariably found that our 

 knowledge, imperfect though it be, of varia- 

 tion under domestication affords the best 

 and safest clue." It was therefore with 

 variation under domestication that he began 

 his book. 



Variation under Domestication. — A 

 comparison between the individuals of a cul- 

 tivated or domesticated "variety" shows a 

 greater degree of variation than there ob- 

 tains between the individuals of a wild 

 species or "variety." The higher variability 

 of domestic productions is to be ascribed to 

 the less uniform conditions of their up- 

 bringing, perhaps in part to excess of food. 



