THE DETERMINATION OF SEX 



characters. Sometimes the demarcation is exactly 

 median, one-half being male and the other female. 

 Such forms are true gynandromorphs. (Fig. 91.) 

 There are cases, however, where the division may be 

 either dorso-ventral or antero-posterior, and still 

 others which show a patchwork of male and female 

 parts, these latter being mosaic or inter-sex individuals. 

 Examples of such sex-intergrades have been found 

 among moths as described by Goldschmidt and by 

 Banta among daphnids. 



Insect gynandromorphs do not necessarily have the 

 gonad of the corresponding sex in their respective 

 halves, showing that the soma is not moulded by sex- 

 hormones. 



The cause of gynandromorphism has been studied by 

 Boveri and by Morgan. Boveri claims to have found 

 in gynandromorph bees of crossed races that the male 

 half was maternal, and the female half hybrid. Obvi- 

 ously, if after the division of the egg-nucleus, a sperm 

 unites with one of the daughter nuclei that half will be 

 female, whereas the sister nucleus, developing partheno- 

 genetically, will form a male half purely maternal in 

 origin. 



This explanation certainly holds good for some cases 

 but Morgan finds in Drosophila that male portions of 

 gynandromorphs often bear paternal characters, genes 

 of which are in chromosomes other than the #-chromo- 

 some. He concludes, therefore, that at times an ^-chro- 

 mosome is lost during the meiosis of a female zygote, 

 leaving a nucleus that fails to get two ^-chromosomes, 

 which, consequently, develops into the male portion of 

 the gynandromorph. 



