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. The question remains, therefore, where are the factors of the somatic sex-characters? One suggestion which might be made is that the female characters are present in the _Y_, in this case female producing chromosome, or, if the female characters are merely negative, that the male characters are in the _X_ chromosome, but only show themselves in the homozygous condition, thus:-- FEMALE x MALE XY XX | \/ | | /\ | XX YX MALE FEMALE The male characters in the male, _XX_, would appear because present in two chromosomes, but would be recessive in the female because present only in one chromosome. The validity of this scheme, however, is disproved by the fact that males can transmit the female characters of their race, as in the case mentioned by Doncaster where a male _Nyssia zonaria_ when crossed transmits the wingless character of its own female.