COMPLETE SEX-REVERSAL IN VIVIPAROUS TELEOST. 



sex-reversal in the domestic fowl is described by the writer 

 (1926) in which no disease whatever is discovered. From the 

 above fact the conclusion is warranted that disease is not a 

 necessary precursor of sex-reversal. 



It seems unquestionably true that the factor or factors which 

 determine and control sex must also determine and control 

 sex- reversal. It seems equally true that such factor or factors 

 are of labile rather than fixed nature. 



The chromosome theory has been considered as an adequate 

 explanation of sex determination and control. It is assumed 

 that sex is determined at fertilization at which the zygote receives 

 the male or female constitution which it maintains for life. 



In the light of data accumulated for such studies as hermaphro- 

 dites, intersexes and particularly from cases of complex sex- 

 reversal, the chromosome theory seems to have reached the 

 limit of flexibility. It is difficult to see how a definite chromo- 

 some composition which determines and controls sex can be 

 completely overridden and still remain as a sex-controlling 

 mechanism. The inadequacy of the chromosome theory finds 

 expression in the often reiterated statement that "sex is not 

 irrevocably decided by the sex-chromosome constitution." It 

 seems logical to expect that there must be something that does 

 decide sex and possibly the 'sex-chromosomes.' 



Proof that maleness and femaleness depends upon the secre- 

 tions of the testes and ovary has been supplied by a number of 

 investigators. Perhaps the clearest cut data have come from 

 castration and transplantation experiments, particularly from 

 the work of Zawadowsky (1922). This author finds that 

 after a total castration of a young cockeral he loses his voice, 

 sex instincts, and head-furnishings and thus assumes an asex- 

 ual or generic appearance. However, if an ovary is success- 

 fully implanted into such castrated male, it will not only assume 

 the appearance of the hen but the graft produces ovocytes as 

 well. In case a young hen is castrated, she will acquire cock- 

 feathers and spurs after the first molting. If however, the 

 castration is incomplete, and the ovary has the chance to re- 

 generate, the bird regains its female furnishings. Hens with 

 total removal of ovary, develop testes as well as external fur- 



