THE ORIGIN OF GYNANDROMORPHS. 61 



fused cross-over X, remained in one cleavage cell which gave rise to the not- 

 vermilion not-bar fused female right side. The other X, the maternal non- 

 cross-over bar X, passed into the other daughter cell and gave rise to the 

 not-vermilion bar not-fused left side. 



- Zygote. Left side. Right side. 



V fu 



B 



B 



No. 937. December 17, 1914. C. B. Bridges. Text-figure 50 (diagram). 



Parentage. — The grandmother was a wild-type XXY female carrying the 

 genes for eosin and vermilion in one X and in the other only wild-type genes; 

 the grandfather was white bar. By equational non-disjunction an XXY eosin 

 daughter was produced which carried eosin and vermilion in one X and eosin 

 in the other. This female was out-crossed to a vermilion male and produced 

 among the sons a mosaic. 



Description. — The mosaic, as in the case B 90, was male throughout, but 

 the left eye was eosin (of the male type) and the right eye was eosin vermilion. 

 The male was fertile when bred to a vermilion female, giving wild-type 

 daughters and vermilion sons (No. 1116). One of the wild-type daughters 

 out-crossed to a forked male gave eosin and vermilion as the main classes of 

 the sons. 



Explanations. — On the hypothesis of a binucleated egg, one nucleus after 

 reduction contained an eosin vermilion X and the other nucleus an eosin X. 

 Since no eye-color corresponded to the X sperm of the father, and since the 

 individual was male throughout, both of the egg-nuclei must have been 

 fert lized by a Y sperm, which is further shown by the fertility of the male. 



Left side. Right side. 



On the view that a single nucleus was present, the following situation de- 

 velops: Since the right eye showed both eosin and vermilion, the mosaic 

 must have contained the eosin vermilion X of the mother. Since the other 

 eye showed eosin (not vermilion), this X must have been the other or eosin X 

 of the mother. That is, both X chromosomes of the mosaic came from the 

 mother by means of an XX egg produced through non-disjunction. The ver- 

 milion X of the father was not present at all, as proved by the fact that the 

 left eye of the mosaic was eosin (not red) and male (not female), and by the 

 breeding-test, which showed that the gonads carried only the eosin X. The 

 sperm was not the X sperm of the father, but the Y sperm, as further indicated 

 by the fertility of the male. 



As in case B 90, there must have been double elimination or somatic re- 

 duction, so that one cleavage-cell received the eosin X and a Y, and the other 





