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. 

 V 



Left side. 



Right side. 

 V 



B 



-X 



.x 



B 



No. 937. December 17, 1914. C. B. Brdges. 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 Sized by a Y sperm, which is further shown by the fertility of the male. 



Left side. 



Right side. 



W< 



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 



