LYMANTRIA DISPAR 39 



M is greater than F, so that in spite of the fact that this 

 individual is XY in sex-chromosome constitution, that is, 

 genetically a female, it will be intersexual; in fact, according 

 to the argument it will be a genetical female completely 

 transformed into, and functioning as, a male. Individuals 

 M4M2F3 are normal males, whilst those which are M^mFj 

 are genetically females, but nevertheless are females trans- 

 formed into males. 



A survey of the Central European and Japanese races of 

 Lymantria has provided Goldschmidt with different strains 

 which possess all kinds of combinations of 'strong' and 

 *weak' male-determining factors, with 'weak' and 'strong' 

 female- determining factors, and by the use of them he was 

 able to produce any percentage of intersexual forms and 

 any grade of intersexuality, either male or female, at will. 

 Whilst in Japan Goldschmidt was enabled to distinguish 

 eight different strains of Lymantria, and an elaborate series 

 of breeding experiments permitted him to arrange them in 

 a series of decreasing strength. The differences between the 

 extremes of this series were greater than those between the 

 European dispar and the L. japonica which he first used. 

 Indeed, it was so great that when a 'strongest' father was 

 mated with a 'weakest' mother, the progeny consisted solely 

 of males, half of these being chromosomally males MgMgF, 

 whilst the rest were really females MgmF in which the 

 male- determining factor, introduced from the strong race, 

 had overwhelmed the female-determining factor of the 

 weaker. The 'strength' or 'valency' of the sex factors differed 

 for each race; but in each race it was fixed. Goldschmidt 

 holds the view that this fixity is really quantitative, depend- 

 ing upon definite amounts of the sex-determining material 

 present in any case. He has satisfied himself that the differ- 

 ent degrees of strength and weakness of these sex-deter- 

 mining factors reveal the existence of a series of multiple 

 allelomorphs, but, more recently, he has been forced to the 

 conclusion that in the case of the mating 'strong' Japanese x 

 'weak' European a pair of autosomal allelomorphic modify- 

 ing genes is involved which affects the expression of male 

 intersexuality. Goldschmidt's results show that the different 



