36 SPECIES NOT 



and rabbits from the common wild duck mid rab- 

 bit. He finishes by a dozen pages upon "selection 

 by man," and sums up by expressing his belief 

 "that the conditions of life, from their action on 

 the reproductive system, are so far of the highest 

 importance as causing variability. "/ do not 

 believe that variability is an inherent <m<l 

 necessary contingency under all circumstances, 

 with all organic beings, as some authors hurt' 

 thought. Variability is governed by in any un- 

 known laws, more especially that of correlation 

 of growth, the effects are modified by inheri- 

 tance and reversion, something is attributed 

 to the direct actions of life, something to use 

 and disuse." And then Mr. Darwin expresses 

 the easily-imagined result as being "thus rendered 

 infinitely complex." Crossing, however, has had 

 something to do with it, but "over all these 

 causes of change I am convinced that the accu- 

 mulative action of selection, whether applied 

 methodically and more quickly, or unconsciously 

 and more slowly but more efficiently, is by far 

 the predominant power." (Page 43.) 



So here we have this unknown power of 

 "natural selection" acting upon an uncertain 

 variability, which is governed by "unknown laws," 

 distinctly Compared with that selection which is 

 applied "methodically" by man, operating in the 

 former case "unconsciously" but "more slowly and 

 efficiently." 



