442 Genetics of Sex Determination 



maphrodites with fertile ovaries and anthers (euhermaphrodites), 

 as opposed to the intersexes or, more correctly, andromonoecists, 

 which show all transitions from hermaphrodites to males. The Y^ or Y^ 

 hermaphrodites selfed produce females without Y and hermaphrodites 

 with Y^ or Y-. From this Westergaard concludes that the missing 

 left segment normally prevents the formation of female organs and con- 

 tains no important male determiners. In Y^ the other end of Y is 

 missing. Plants with Y^ are always rudimentary (sterile) males. From 

 this it is concluded that the "genes" contained in this segment control 

 the last stages of pollen formation without an e£Fect upon the female 

 organs. Thus the differential segment of the Y-chromosome is as- 

 sumed to have three diflFerent functions. Segment I exclusively has the 

 function of preventing the normal development of the female organs; 

 segment III contains the genes needed for complete development of 

 pollen; segment II, in between, "must" therefore contain the genes 

 controlling the formation of anthers, since, in the absence of the 

 entire Y, anthers are "never" formed. But Westergaard himself men- 

 tions spontaneous 2X hermaphrodites found by Akerlund, but dis- 

 misses them on the assumption that one X is really a rudimentary Y. 

 However, he should also have mentioned Strasburger's intersexual 

 females by Ustilago infection, which cannot be interpreted in such a 

 way. 



Actually, these facts lead to an interpretation which I consider to 

 be far superior to Westergaard's, because it fits the facts into the 

 general well-established system of sex determination by F/M balance, 

 instead of denying the proved method of sex determination in animals 

 on the basis of a single case, only slightly aberrant, and, in my opin- 

 ion, misinterpreted. In Drosophila, where the balance system has been 

 established beyond any doubt, the Y-chromosome also consists of 

 sections of different functions (Stern, 1929^?); some of them are re- 

 sponsible for "fertility," since their absence results in male sterility. 

 Westergaard considers this a proof of the presence of male factors in 

 the Y-chromosome after all! But Stern and Shen (see Shen, 1932) 

 showed that this "steriHty" is nothing but the absence of motility of 

 sperm. 



Since in both Drosophila and Melandrium a definite section of the 

 Y-chromosome is needed for the accomplishment of a comparable last 

 step in male gamete formation, the explanation is expected to be the 

 same. In both cases, without Y in Drosophila and without Y'' in 

 Melandrium, the sex is completely male in every respect. Wliat is 



