108 J. -M. ESSENBERG. 



nishings of the male within four to five months. Castrated hens 

 with implanted testes acquire male furnishings and if the trans- 

 plantation is successful, the graft produces active spermatozoa. 



From these and other experiments of similar nature which he 

 has carried on with mammals, Zawadowsky concludes as follows: 

 "Aus meinen Versuchen bin ich geneigt Hinweise darauf zu 

 ersehen, dass hinter den Symbolen der ' Geschlechtsgene ' F 

 (female) und f (male) die geschlechts hormonen- Feminism und 

 Masculinisin zu suchen sind." 



With the above statement the present writer is in full accord 

 and wishes to add that with the replacement or substitution, 

 if you please, of feminisin or the female hormone for the gene- 

 anatomy represented by X and masculinisin or male hormone 

 for the qualities of Y, the problems of sex are brought in accord 

 with present knowledge of bio-chemistry and endocrinology. 

 By so doing we not only gain an insight into the mechanics of 

 the various types of hermaphrodite, of "intersex," and sex- 

 reversal cases, which thus far have been a source of puzzle and 

 speculation, but we also gain a better understanding of the 

 science of genetics. 



In conclusion, it may be said that there is no particular disease 

 associated with sex-reversal. Any adverse condition be it 

 extrinsic or intrinsic, acquired or inherited, which tends to reduce 

 the capacity for hormone production beyond a certain limit may 

 automatically become the immediate cause in sex-reversal in the 

 female of Xiphophorus helleri. 



VI. SUMMARY. 



1. Two cases of complete sex-reversal, from female to male, 

 in adult Xiphophorus helleri have been described. 



2. It is definitely known that both fish gave birth to normal 

 young prior to sex- reversal. 



3. It is also definitely known that both fish fertilized virgin 

 females which gave birth to young with sex-ratio typical of 

 the species. 



4. The transformed fish is indistinguishable from a "normal" 

 male except body form which is that of a female. 



5. The entire ovary disintegrates except the epithelium of the 



