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 cells 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 ‘the silk-worm moth 
(Fig. 367) call for this type of explanation 
(Fig. 36 J). In this connection it is interesting 
to note that Doncaster has found binucleated eggs 
