8 THE ORIGIN OF GYNANDROMORPHS. 



("short" type) . The mother had one sex chromosome with the dominant 

 gene for notch and another sex chromosome that had the normal allelo- 

 morph of notch and also a gene for eosin eye-color. The gynandromorph 

 was male on one side, with an eosin eye (with a red fleck in it), a sex- 

 comb, and a short wing on that side, and female on the other side with a 

 red eye, no sex-comb, and a longer wing. The genitalia were male. 

 The gynandromorph arose by the fertilization of an egg containing the 

 sex chromosome bearing the eosin eye-color (because had the other 

 maternal X chromosome been present one of the wings, or both, would 

 have shown the notch character). In this case it was the X chromo- 

 some from the father that was eliminated, since the male side shows 

 the eosin eye-color of the maternal sex chromosome. Boveri's ex- 

 planation will not fit this case, even though the male side shows a 

 maternal character, viz, eosin eye, because that side is dichsete, hence 

 contains dominant factors from the paternal autosome. Morgan's 

 hypothesis of polyspermy will not fit this case, for the male side should 

 have red instead of eosin eye-color, since red was brought in by the 

 sperm. On the hypothesis of elimination, it is apparent that one of 

 the daughter halves of the normal X chromosome was lost; the cells of 

 both sides got the regular autosomal groups, for dichaete came from the 

 father. The father was heterogyzous for star, and it must have been 

 one of his gametes without star, but with dichsete, that fertilized the egg. 

 Here again neither of the earlier explanations fits the case, but the 

 third hypothesis covers it. 



Another gynandromorph was described in "Mosaics and Gynandro- 

 morphs in Drosophila" in 1914. It was the first case discovered in 

 which the presence of an autosomal factor made it possible to decide 

 which of the three explanations was the correct one. A yellow white 

 female was crossed to a male that carried a recessive autosomal gene 

 for ebony body-color. The gynandromorph was preponderantly male 

 on one side and female on the other. Both eyes were red and the 

 body-color was gray (or possibly heterozygous ebony) on both sides. 

 Here Boveri's explanation fails, because the male side should have 

 been entirely maternal, therefore yellow and white; and Morgan's 

 earlier explanation fails, because the male side was not ebony. On 

 the elimination hypothesis a maternal yellow white daughter chromo- 

 some was lost; hence both sides had red eyes and not yellow body-color, 

 and both sides received the same normal autosomes. This cross, 

 in which a yellow white female was mated to an ebony male, was 

 carried out extensively (January to May 1914) and 6 more gynandro- 

 morphs were found. However, in order to discriminate between 

 partial fertilization and polyspermy on the one hand and elimination 

 on the other only those cases are diagnostic in which the male parts 

 come from the father and show at the same time autosomal parts from 

 the mother. 



