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THE AMEBIC AN NATURALIST [Vol. XLV 



may have direct touch with Lamarckian ideas, as, e. g., 

 De Vries 's selection of buttercups, recently quoted by 

 Jennings as "the only case that he has found" indi- 

 cating hereditary action of selection: "Here, after 

 selection the extreme was moved far beyond that before 

 selection." And Jennings says: "Possibly repetition 

 with thorough analytical experimentation will show that 

 something besides selection has brought about the great 

 change. But at present the case stands sharply against 

 the generalizations from the pure line work." 



Certainly Jennings is in reason, when he, on the 

 ground of his own masterly researches, looks out for 

 "something besides selection." There are three direc- 

 tions for the inquiry here. First, the strong evidence 

 that the buttercup-population was not at all homogene- 

 ous. Secondly, the possibility of intercrossing. I only 

 need to point out the beautiful researches of Shull as to 

 the effect of intercrossing in maize. The heterozygotes 

 were here larger and more productive than the pure 

 strains. The surprises of heterozygotic "constructions" 

 or of new combinations in F 2 may perhaps be respon- 

 sible for the case of De Vries 's buttercups ; I shall not 

 try to discuss it. But, thirdly, we have an instance 

 pointed out several times by De Vries himself, viz., the 

 combination of selection with nourishment: "la selection 

 c'est 1 'alimentation" as it has been said. I suppose that 

 we have here the essential point. The buttercups in cul- 

 ture have been better nourished than before the experi- 

 ments. Hence, the "best" genotypes having been se- 

 lected from the population and submitted to "better 

 nourishment, the result would easily be a moving of the 

 extremes far beyond those before selection. The butter- 

 cup-case seems to me to present no difficulties for the 

 genotype-conception. 



The practical breeders are a somewhat difficult people 

 to discuss with. Their methods of selection combined 

 with special training and "nurture" in the widest sense 

 of this word are mostly unable to throw any light upon 

 questions of genetics, and yet they only too frequently 



