REPRODUCTION AND HEREDITY 133 



linked, and are due to the absence of one .r-chromosome in 

 the cells producing those parts of the body which show 

 male features. It follows from this that the gynandro- 

 morph must be considered as originally a female with the 

 two ;c-chromosomes ; if in the repeated cell-divisions 

 leading to development one of these be accidentally 

 " dropped out," male features will appear. It is note- 

 worthy, however, that in a bilateral g\^nandromorphic 

 Drosophila only the outward male characters are present. 

 Internally there are right and left ovaries. Where the 

 distribution of the two sex-characters in a gynandromorph 

 Drosopliila is mosaic and irregular, the female areas always 

 predominate ; this confirms the conclusion that the cell 

 division or divisions in which one of the .y- chromosomes 

 " dropped out " came later in development than the 

 primary division of the egg, and it also confirms the 

 originally female nature of the gA'nandromorph. 



Various abnormal hybrid moths afford examples of a 

 mixture of male and female characters which differ in more 

 important respects from the cases hitherto mentioned, as 

 the most remarkable forms show a tendency to trans- 

 formation from one sex to the other ; it is therefore con- 

 venient to distinguish them from g\'nandromorphs, and 

 they have become generally known in recent years as 

 " intersexes." The best known work on such insects is 

 that of R. Goldschmidt (1916-17, 1923), who has made 

 extensive breeding experiments with various races of the 

 Gipsy Moth {Porthetria dispar). As is implied in its 

 specific name, this insect shows very marked sexual differ- 

 entiation, the female having whitish wings with black cross- 

 markings and feebly pectinate feelers, while the male's 

 feelers are strongly pectinate and his wings show a dark 

 brown ground colour on which the black banding is 

 relatively inconspicuous. The species has a ver^^ wide 

 range from Western Europe to Japan (the indigenous 

 British race is extinct), and shows well-marked geographical 

 forms. In Goldschmidt's experiments, various Japanese 

 varieties were cross-bred with the European forms of the 



