SHORTER ARTICLES AND DISCUSSION 



CAN SELECTION CAUSE GENETIC CHANGE? 



It is almost a pleasure to have occasion for controversy with a 

 fellow worker who shows himself so fair-minded and generous 

 an opponent as does Dr. Pearl in the American Naturalist for 

 February, 1916. He credits my investigations with greater 

 merits than I have claimed or can claim for them. If they pos- 

 sess any superiority, it is not because they have been either better 

 planned or better executed than Dr. Pearl's, but only because the 

 material used was more favorable. In my experiments with rats 

 I have simply undertaken a less difficult task than that under- 

 taken by Dr. Pearl in relation to the fecundity of fowls. Pearl 

 is right in supposing that I have no desire to convey the impres- 

 sion that his work is valueless. No one has greater admiration 

 than I for the masterly way in which he has analyzed the funda- 

 mental problems of genetics and the thorough and systematic way 

 in which he has attempted their solution. I regret only that he 

 has courageously attacked so complex a problem before certain 

 simpler and more elementary ones had been solved. I felicitate 

 myself only on having been content with a less ambitious pro- 

 gram. 



I am pleased to learn too that we are so closely in agreement 

 as regards the observational facts, that in reality it is only con- 

 cerning the interpretation of results that our views seriously 

 differ. 



I am quite ready to grant that we are concerned with the same 

 fundamental question, that of the possible quantitative change 

 in a character under selection, that the methods which we have 

 employed are substantially the same and that these methods are 

 open to similar objections, that random sampling occurs in the 

 rat experiments as well as in those with fowls, though it is in- 

 volved in a further degree in the experiments with fowls because 

 of limitations of age and sex. I am quite willing that Pearl 

 should recall the statement "that phenotypic variation of the 

 character fecundity in fowls, markedly transcends, in extent and 

 degree, genotypic variation," and that he should substitute in 

 its stead the statement that it "may" so transcend. I am even 

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