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THE AMERICAN NATURALIST [Vol. LII 



Bellamy, working in the same laboratory, contributes also an 

 excellent study on the same subject, but based on a different 

 genus of Tetrigince (Bellamy, '17). Both he and Nabours have 

 apparently accepted as proven that there is here a large group 

 of determiners allelomorphic to each other, and I am quoted in 

 support of this idea. Inasmuch, however, as I made certain 

 reservations which are important in the light of the new data pre- 

 sented, I beg to quote a portion of my former paper. 



As Sturtevant has pointed out, for any ease to which the idea of 

 multiple allelomorphism is applicable, an equally valid explanation 

 may be found in " complete linkage " of the factors concerned. To 



If however linkage were not complete, a "cross-over" class . . . 

 might occur, and this would suffice to rule out the explanation based on 

 multiple allelomorphs. Such a cross-over class perhaps is furnished 

 by the BEI individual. 



I then suggested that since the BEI individual had been lost 

 before it could be tested, the cross be repeated, and said : 



If then BEI forms should occur again, and in these, when mated to 

 other forms, the factors B and I should be found to stay together to 

 the same extent as before they separated, it would show that close 

 linkage rather than multiple allelomorphism explains this particular 



Nabours has repeated this experiment, using the character S 

 instead of E, and has again obtained such a cross-over, BIS. 

 With this individual, he has carried out breeding tests. 



Apparently forgetting what had been pointed out in my paper, 

 he says: 



The significant feature is the complete combination or linkage, ap- 

 parently permanent, of the factor for S, and the factor for the modi- 

 fied I. . . . This combination, IS, becomes a new form, a new multiple 

 allelomorph (italics not original), pairing with and allelomorphic to 

 any other multiple allelomorph with which it has been tried. ... It is 

 not possible for me to suggest the means by which the combination or 

 linkage was effected. 



(One must protest against the use of words which permits a 

 single determiner to be called a "multiple allelomorph.") 



The answer that he was unable to give is obvious. Perhaps 

 there are thirteen characters here whose determiners are allelo- 

 morphic to each other. That is possible, perhaps probable, 



