Homozygous. B male B male X b female b male B male b female b male b male Barred female. Barred male. Heterozygous. This case is thus exactly similar to that of Abraxas grossulariata and A. lacticolor.
He also discusses the case of Abraxas grossulariata and its variety lacticolor, and other cases of sex-linked heredity, apparently with the idea that all such cases are similar to those of sexual dimorphism.
One example in the barred character of the feathers in the breed of fowls called Plymouth Rock. In this the female is heterozygous for sex as in Abraxas grossulariata, and the barred character is sex-linked. When a barred hen is crossed with an unbarred cock all the male offspring are barred, all the females plain.
It will be seen that although in the progeny of this mating all the grossulariata were males and all the lacticolor females, yet this case is by no means similar to that of sexual dimorphism in which the characters are normally always confined to the same sex. For the lacticolor character in the parent was in the male, while in the offspring it was in the female. Univ.
Bateson's explanation is that the female, according to the Mendelian theory of sex, is heterozygous in sex, the male homozygous and recessive, and that lacticolor is linked with the female sex-character, grossulariata being repelled by that character. Thus we have, the lacticolor character being recessive,
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.
The barred character like grossulariata is dominant, the unbarred recessive, and to explain the results it is necessary to assume that the female is not only heterozygous for the barred character, but also for sex, with the female sex-factor dominant.