Ii6 EVOLUTION 



relations, their geographical distribution, geo- 

 logical succession, and such other facts, might 

 come to the conclusion that species had 

 not been independently created, but had 

 descended like varieties from other species. 

 Nevertheless, such a 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 perfection 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 modification and co- 

 adaptation. At the commencement of my 

 observations it seemed to me probable that 

 a careful study of domesticated animals and 

 cultivated plants would offer the best chance 

 of making out this obscure problem. Nor 

 have I been disappointed: in this and in 

 all other perplexing cases I have invariably 

 found that our knowledge, imperfect though 

 it be, of variation 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 



