These results, almost incredible as they appear, are in harmony with the
relatively frequent occurrence of gynandromorphism in insects.[Footnote:
See Doncaster, _Determination of Sex_ (Camb. Univ. Press, 1914), chap.
ix.] One of the most remarkable cases of this is that of an ant
(_Myrmica scabrinodis_) the left half of which is male, the right half not
merely female, but worker--that is, sterile female, without wing. Cases in
Lepidoptera, _e.g. Amphidasys betularia_, have frequently been recorded.
Presumably not only the antennae and markings, but also the genital
appendages and the gonads themselves, are male and female on the two
sides. On the view that both sexes and the somatic sex-characters of both
sexes are present in each zygote, and that the actual sex is due to
dominance, we must conclude that the male primary and secondary characters
are dominant on one side, and the female on the other, and it is evident
that hormones diffusing throughout the body cannot determine the
development of somatic sexual characters here. Various attempts have been
made to explain gynandromorphism in insects in accordance with the
chromosome theory of sex-determination. These are discussed by Doncaster
in the volume already cited, but from the point of view of the present
work the important question is that concerning the somatic sex-characters.
According to Doncaster it has been found that in some Lepidoptera the
different sex-chromosomes occur in the female, not in the male as in other
insects. Half the eggs, therefore, contain an X chromosome, and half a Y,
while all the sperms contain an X chromosome. Doncaster has seen in
_Abraxas grossulariata_ ova with two nuclei both undergoing maturation.
If one of these in reduction expelled a Y chromosome, the other an X,
then one would retain an X and the other a Y. Each was fertilised by a
sperm, one becoming therefore XX or male and the other XY or female. It
may be supposed that as there was only the cytoplasm of one ovum, each
nucleus would determine the characters of half the individual developed.