SEX INHERITANCE 121 



or abdominal region may be due to the shifting of 

 nuclei in embryonic development. 



Previous explanations of gynanders have involved 

 the use of whole nuclei, and have postulated that 

 the male parts are haploid, and the female parts 

 diploid. The gynanders of Drosophila have been 

 explained by the behavior of an intra-nuclear 

 element — the X chromosome — and the celjs of 

 both sexes remain diploid for the autosomes. That 

 both maternal and paternal autosomes were present 

 in both male and female parts of the Drosophila 

 gynanders was decisively proved in certain cases 

 by the introduction of autosomal characters as well 

 as sex-linked characters. In the gynanders that 

 arose in such crosses both sex-regions showed the 

 same condition with respect to these autosomal 

 characters. 



There are a few gynanders in Drosophila that 

 can not be explained by simple elimination; but 

 another explanation appears to cover such cases, 

 namely that two nuclei were present in the egg 

 before fertilization. If one of these nuclei was 

 fertilized by an X-sperm and the other by a Y- 

 sperm the two halves of the resulting embryo may 

 be of different sexes, and even display different sex- 

 linked characters according to the constitution of 

 the two nuclei. The two interesting gynanders 

 described by Toyama in tlie silk- worm moth 

 (Fig. 36/) call for Ihis type of explanation 

 (Fig. 36 ./). In this connection it is interesting 

 to note that Doncaster has found binucleated eggs 



