No. 600] EXPERIMENTAL INTERSEXUALITT 707 



into the other, or are they nothing but limiting points of 

 a series, which might approach each other or even become 

 interchanged? These and many other questions can only 

 be approached by experimental modifications of the 

 normal sex conditions. There is one road towards this 

 goal, the application of the well-known influence of the 

 internal secretion of the sex-glands upon the sex-char- 

 acters in castration- and transplantation-experiments, 

 as well as the study of analogous experiments by nature. 

 Another approach is rather an unexpected one ; this has 

 been followed in my experiments, an account of which I 

 now have the pleasure of giving you. 



Insect-breeders have long known that in crosses of 

 species as well as of geographic varieties a comparatively 

 high percentage of sexual abnormalities are produced. 

 Furthermore, any collector of moths knows that similar 

 abnormalities, usually called gynandromorphs or hermaph- 

 rodites, appear occasionally in nature and one of the 

 moths in which these occur is the gipsy-moth. Since this 

 moth has a very wide range of geographic distribution 

 through very different climates a considerable differ- 

 ence of geographic varieties is to be expected. Fur- 

 thermore, as is well known, the sexes are extremely 

 dimorphic. Therefore, seven years ago I began hy- 

 bridization experiments of European and Japanese 

 gipsies. I was rather fortunate in striking the right 

 forms which gave, from the outset, the most interesting 

 results. 



The first result was that crosses of Japanese females 

 with European males yielded normal offspring, whereas 

 m the offspring of the reciprocal cross, European female 

 X Japanese male, all males were again normal, but all 

 females showed in all parts of their bodies admixtures 

 of male characters. I first called these animals gynan- 

 dromorphs. But as this term is usually applied to 

 animals with bilateral or antero-posterior or similar 

 mosaic of the two sex-characters, it seems advisable to 

 use another term for these forms, which in general repre- 



