160 EVIDENCE OPPOSED TO 



Presumably not only the antennae and markings, but 

 also the genital appendages and the gonads them- 

 selves, are male and female on the two sides. On 

 the view that both sexes and the somatic sex-char- 

 acters 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 develop- 

 ment of somatic sexual characters here. Various 

 attempts have been made to explain gynandro- 

 morphism in insects in accordance with the chromo- 

 some theory of sex-determination. These are dis- 

 cussed by Doncaster in the vohime 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, con- 

 tain an X chromosome, and half a 7, 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 X Y or female. It 

 may be supposed that as there was only the cyto- 

 plasm 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 



