34 SEX-DETERMINATION 



among the offspring of the mating of European Lymantria 

 females and Japanese Lymantria males. This mating gave 

 normal sons and individuals showing a mixture of male, 

 female and intermediate characters. 



It has long been known to entomologists that crosses 

 between different geographical varieties of the Gypsy moth 

 sometimes yield these sexually aberrant forms. This inter- 

 sexuality is in no way associated with any corresponding 

 abnormality in respect of chromosome number or be- 

 haviour. The female is the heterogametic sex. Goldschmidt 

 (1920, 1 93 1, 1934) was able to classify the intersexes 

 according to their characterizations into two main types, 

 male intersex and female intersex, the former being an XX 

 individual which exhibits female as well as male characters, 

 the latter an XY individual with both female and male 

 characters. The intersex is a sex mosaic. The female inter- 

 sexes range from the unexceptional female, through 

 increasing grades of intersexuality — i.e. with increasing 

 degrees of maleness — to complete sex-reversal — i.e. an XY 

 individual that is a functional male. A corresponding series 

 of male intersexes ranges from complete maleness to 

 complete femaleness. 



A careful examination of great numbers of intersexual 

 individuals permitted Goldschmidt to conclude that there 

 was indeed a time seriation of events in the development of 

 the sex-characters — that is to say, that all the structures of 

 the sex equipment were not differentiated at any one time 

 but that one structure of this equipment appeared before 

 another, and so on, and that the grade of intersexuality was 

 determined by the relative number of these structures that 

 were male and female in type respectively. It appeared that 

 the last structure of the sex-equipment to become differ- 

 entiated in the life history of the individual was the structure 

 most commonly affected in this process of intersexuality, 

 and that a greater number of these structures became 

 affected with each increasing grade of intersexuality. 



The original matings on the results of which Gold- 

 schmidt's hypothesis is founded were as follows: 



