60 HEREDITY 



CHAPTER VII 

 MENDELISM 



As is asserted at length in another volume,^ the 

 theory of organic evolution was re-stated by Darwin 

 in 1859, in a form which has stood the test of the 

 most intellectually active decades in history. Dar- 

 win took for granted the existence of variations, and 

 showed how animal and vegetable species might 

 have their origin in the selection of such variations 

 as were advantageous in the struggle for existence. 

 This theory of natural selection is now a truth ques- 

 tioned by no competent and very few incompetent 

 critics. This granted, it is seen to be a matter of 

 prime importance for evolutionary theory, as we 

 have already observed, that we should determine 

 the causes of variation, and formulate the laws of 

 variation — if such there be — as no man of science 

 can doubt. But during nearly all these past years 

 the subject has been almost ignored — overshadowed 

 by the colossal controversy concerning the fact of 

 organic evolution in general, and the Darwinian con- 

 tribution to its explanation in particular. Latterly, 

 however, the controversy ended, and ended con- 

 clusively, as all controversies about verifiable or 

 rational matters ultimately must, and biologists 

 were free to devote more attention to the cardinal 

 and initial fact of variation — upon which the whole 

 theory of natural selection is based. 



Then " a curious thing happened," and it was found 



1 See " Organic Evolution " in this series. 



