324 THE AMERICAN NATURALIST [Vol.L 



tion occurs within these "pure lines" (see Table I). For 

 in all but the last two of the thirteen cases tested the 

 earlier parent has the earlier progeny. From long ex- 

 perience in studies of rats with such small differences as 

 are here indicated I have no hesitation in concluding that 

 fluctuating variation of genetic significance is here in 

 evidence. 



To recapitulate, as regards genetic variation in flower- 

 ing time, Hoshino (1) recognizes that gametic contami- 

 nation results from crossing early and late flowering 

 varieties; (2) recognizes also that variation may occur 

 among the cross-bred families, as well as in different 

 pure lines of the uncrossed races, as regards the "qual- 

 ity," value, or potency of the same gene. (3) Although 

 Hoshino does not refer to the fact, his observations show 

 clearly that genetic variation of a graded or fluctuating 

 sort occurs in at least one of the varieties which he 

 crossed. It is probable that those varieties were as pure 

 as are obtainable, but almost certain that their flowering 

 time fluctuates slightly from genetic causes. 



What I want to suggest is that in these several agen- 

 cies we have a sufficient explanation of the variations 

 observed in Hoshino 's F 2 , F 3 , and F 4 generations, with- 

 out invoking a two-factor hypothesis, one factor being 

 enough. Hoshino has shown that a three-factor, or 

 multi-factor hypothesis will not fit the facts observed. 

 Will not one factor fit them quite as well as two, pro- 

 vided gametic contamination occurs, which he admits t The 

 "pseudo-early" and "pseudo-late" classes Hoshino ex- 

 plains plausibly as due to gametic contamination. Could 

 not the "intermediate early" and "intermediate late" 

 be reasonbly explained as due to further contamination? 

 For they intergrade with the pseudo-early and pseudo- 

 late classes, respectively, and also with each other. From 

 Hoshino 's carefully controlled results, it is perfectly 

 clear that early and late flowering are allelomorphs, and 

 that segregation of early and late types occurs in F 2 but 

 attended by gametic contamination. It is perfectly clear 

 that the contamination is not uniform in amount. Some- 



