No. 534] 



THE PURE LINE THEORY 



853 



which have been adduced in support of the genotype 

 theory. These arguments and the evidence upon which 

 they rest must be examined. For convenience of treat- 

 ment I do this under three propositions concerning selec- 

 tion, which seem so reasonable that I believe few biol- 

 ogists will feel inclined to deny their soundness. They 

 are at least so reasonable that no worker can afford to 

 leave them out of consideration. 



A. Characters ivhich are not Inherited at all can not be 

 Taken to Prove that Selection in General is 

 Ineffective 



This is a point of great importance, generally ignored 

 by pure-linists. Biometrieians have long known that of 

 the variations of any character whatever not all are in- 

 herited. 18 They have also learned that variations in cer- 

 tain characters are not inherited. 



Suppose now that one takes a character which gives 

 no correlation between its degree of development in 



