330 Dr. E. A. Cockayne on 



One was bred at Wiesbaden and is described by Schultz, 

 right side male and left side female; another was described 

 and figured by Birchall. Neither of these had ova in the 

 abdomen, though the female side was fuller than the male 

 side. 



Two others were bred from the same parents by Mr. 

 Sydney Whicher : one has been described in the previous 

 part of this paper, the other is figured in the Entomologist, 

 1915. In these both sides show both maternal and paternal 

 characters. 



In heterochroic gynandromorphs the one side or part 

 is of one sex and shows a colour variation often a Mendelian 

 dominant, which is not sex-linked, and the other side or 

 part shows the corresponding Mendelian recessive colour 

 and is of the opposite sex. Many of these are known, but 

 the exact parentage has been recorded but seldom. Four 

 were obtained in one brood of Hemerophila abrwptaria by 

 Simmons, from a cross between a light and a dark parent. 



1. Right side male and ab. brunneata, Tutt. (melanic), 



left side female and typical. 



2. Right side male and ab. brunneata, left side almost 



entirely typical and female. 



3. Right side female and ab. brunneata, left side male and 



typical. 



4. Right side male and ab. brunneata, left side female and 



typical. 



The melanic ab. brunneata is dominant over the buff- 

 coloured typical form, and the parents must have been a 

 homozygous recessive and a heterozygous dominant for 

 colour. The combinations of colour and sex in these 

 gynandromorphs could not have arisen except by both 

 sides having received characters from both parents. 



The suggestion put forward by Doncaster that a gynan- 

 dromorph arises from the fertilisation of an ovum possess- 

 ing two nuclei by two spermatozoa is possible, and would 

 explain the occurrence of heterochroic insects, simple 

 gynandromorphs and heterochroic gynandromorphs. Don- 

 caster has demonstrated the existence of such ova and 

 shown that both nuclei can be fertilised independently. 

 It is, however, very improbable that the two nuclei of 

 such an ovum would be different in constitution, and unless 

 this were the case heterochroic gynandromorphs like the 



