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THE AMERICAN NATURALIST [Vol. XLIX 



three allelomorphs, but using G in each of the two cases to rep- 

 resent a different factor of the gray mouse. 3 This method is in 

 itself quite legitimate, but as a result when Cuenot later spoke of 

 the factor for gray, gray white belly, yellow, and black, all as 

 allelomorphic, some of us, it appears, failed to appreciate that in 

 doing so Cuenot was treating this set of terms in an entirely differ- 

 ent way from the way in which he treated the other cases, where 

 he had represented factors as allelomorphic to each other. In the 

 second place, the full significance of multiple allelomorphs in mice 

 was not, I think, fully appreciated until its relation to complete 

 linkage became apparent, and in fact even now this relation is not 

 sufficiently understood by many geneticists themselves. Even, 

 however, had I taken fully into account all that Cuenot had done, 

 the somewhat extensive experiments that I undertook in order to 

 prove that the factors in question are allelomorphic would have 

 seemed to me necessary, as they still do, to establish that this 

 series of factors bears this relation to each other. Let us ex- 

 amine, therefore, the evidence, which, according to Mr. Little, 

 rendered my experiments a work of supererogation. 



1. Little says : 



As early as 1903 Cuenot recognized that albinos, potentially yellows, 

 when crossed with black gave besides yellow offspring either black or 



agouti and black 1 are all allelomorphic to one another. 

 But the evidence proves nothing of the sort, unless Cuenot had 

 shown that his albinos should have been expected from their 

 history to contain all three factors in question. However likely 

 it may seem, to one so inclined, that such triple forms must sooner 

 or later have been met with by chance, the fact remains that 

 Cuenot had, as the offspring showed, used only double types, and 

 such a fact in the absence of explicit evidence as to the history 

 of the forms used can not be said to demonstrate anything in 

 particular. 



2. Little continues : 



agouti factor. If so he refers to a different factor from that which he 



