THE ORIGIN OF GYNANDROMORPHS. 73 



In the early stages of non-disjunction, C. B. Bridges fJourn. Exp. Zool, 

 Nov. 1913) found several gynandromorphs, two of which (N2 and (N3) have 

 been figured in Heredity and Sex (p. 1G3) and refigured here. Breeding-tests 

 were tried on all these and it was shown that some were fertile, and further 

 that the gynandromorphs were not due to an inherited condition. It was 

 pointed out (p. 600) that such mosaic forms can be explained as due to 

 somatic non-disjunction and also even to XXX zygotes. 



Again, in the experiments on "Dilution Effects on Certain Eye Colors" 

 (Morgan and Bridges, J. E. Z., Nov. 1913), about a dozen gynandromorphs 

 were recorded, most of which were sterile, but those which bred (as females) 

 behaved genetically as did their regular sisters; that is, they showed no trace 

 in their gonads of the effect of the bodily division. This was especially strik- 

 ing in one case where the head was entirely white, yet in which the offspring 

 showed eosin (pp. 44, 51). 



No. I. F. N. Duncan. (See Am. Nat., vol. 49, p. 455, 1915.) 



Parentage. — The father had white eyes, the mother was wild-type. 



Description. — The fly had on one side a red eye, long wing, no sex-comb, 

 and female abdomen. On the other side white eye, short wing, sex-comb, 

 and male abdomen. Courted by males but would not court. Two testes 

 with ripe sperm. 



Explanations. — Elimination of a maternal X chromosome explains the 

 results. 



No. II. F. N. Duncan. Plate 3, figure 5 (colored drawing). 



Parentage. — The male grandparent was cherry club vermilion, the female 

 wild-type. The mother was heterozygous for the above genes. The father 

 was wild-type. 



Description. — The fly had a cherry left eye and red right eye. Sex-comb 

 on left foreleg only. Right wing shorter than left. Abdomen largely 

 female, more female left, more male right. Contained two testes with 

 immature sperm. 



Explanations. — An egg containing a cross-over cherry X was fertilized by 

 an X sperm. Elimination of a paternal chromosome followed by an irregular 

 distribution of the nuclei with one sex chromosome explains the results. 



No. III. F. N. Duncan. 



Parentage. — Same origin as No. II. 



Description. — The fly had red eyes and sex-combs, left wing longer, abdomen 

 male. Genitalia half male, half female. Was courted but would not mate. 

 Two ovaries with ripe eggs. 



Explanations. — EHmination of either a maternal or a paternal X chromosome 

 will explain the result. 



No. IV. F. N. Duncan. 



Parentage. — Same origin as No. II. 



Description. — Both eyes red, no sex-combs, wings same length. Abdomen 

 and genitalia male on one side, female on other. Was courted. Two testes 

 with mature sperm. 



Explanations. — It is not possible to determine which X chromosome was 

 eliminated. 



No. I. 1915. Hyde and Powell. Genetics, I, 1916, p. 580 (colored diagram). 



Parentage. — The mother was pure for blood, an allelomorph of white. 

 The father was eosin, another allelomorph of white. 



