No. 569] NOTES AND LITERATURE 



310 



A and B; BF gives B and etc. In other words, he treats the 

 matter as if he were dealing with a system of multiple allelo- 

 morphs, though he nowhere specifically calls them such. From 

 this point of view there are eight distinct allelomorphs con- 

 cerned with color pattern any two of which may constitute a 

 pair; in any zygote two allelomorphs (perhaps alike, perhaps 

 unlike) will be present, and in any gamete only one of the eight 

 will normally occur. 



With one exception of which I will treat later, all of Nabours's 

 results can be explained by this hypothesis. This sort of explana- 

 tion is not new. (Shull ('11), de Meijere ('10), Sturtevant 

 (13) and others have used it to explain results obtained in 

 Lychnis, Papilio, rabbits and other forms, and it will almost un- 

 doubtedly be shown to apply satisfactorily in still other cases. 



The exception just mentioned occurred in the cross which 

 Nabours describes at the bottom of page 156 (e). Here a male 

 of the constitution CE was mated to a female of the constitution 

 BI. On Nabours's theory, the gametes of the male should carry 

 C or E, but not both, and the gametes of the female should carry 

 B or J, but not both. The union of the two kinds of sperms with 

 the two kinds of eggs should give four classes of offspring, and 

 these were in fact obtained; viz, 12 BC, 11 BE, 7 CI, 10 El. But 

 there appeared also one individual BEL Nabours's explanation 

 of the case is that perhaps the BI "female parent gave at least 

 one gamete containing the factors for the patterns of both her 

 parents and that this double character gamete was fertilized by 

 one of the E gametes which came from the CE male." 1 Let us 

 see whether this is the most probable interpretation. 



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

 of multiple allelomorphism is applicable, an equally valid ex- 

 planation may be found in "complete linkage" of the factors 

 concerned. To decide in any case between the two explanations 

 would be impossible. 



If, however, linkage were not complete, a - cress-over" class or 

 "recombination" 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 UFA 

 individual. The demonstration of this may be given by the use 

 of symbols, as follows : 



Let us assume that A is the allelomorph of a, B that of b. C of 

 c, D of d, F of /, / of i, etc., making ei-ht pairs of a j lel ° m °^ 



