THE INFERTILITY OF RUDIMENTARY WINGED 

 FEMALES OF DROSOPHILA AMPELOPHILA 



PROFESSOR T. H. MORGAN 

 Columbia University 



While the infertility of the females of the mutant stock 

 of Drosophila called rudimentary, was apparent from the 

 beginning, the cause of the infertility was uncertain. Many 

 rudimentary females bred to males of their own kind gave 

 no offspring. The males with rudimentary wings, on the 

 other hand, were perfectly fertile with wild females and 

 with females of other stocks. The results might seem to 

 show that sperm bearing the factor for rudimentary could 

 not fertilize the eggs carrying the same factor. But that 

 this was not the entire explanation was evident : for, he- 

 terozygous females fertilized by rudimentary males gave 

 rudimentary females and males as well as long winged 

 flies. In the heterozygous females, however, the egg, up 

 to its maturity, has developed under the influence of the 

 normal allelomorph of rudimentary, as well as of the rudi- 

 mentary factor. I suggested, 1 therefore, that, due to this 

 difference during the ripening period, the rudimentary 

 bearing egg of the heterozygote could be fertilized by the 

 rudimentary sperm, although the egg of the rudimentary 

 female itself could not succeed in this combination, but I 

 have never felt satisfied with this tentative explanation; 

 for, there were other possibilities, not sufficiently studied, 

 that might affect the result. For instance, it was not 

 actually observed that the rudimentary males copulate 

 successfully with females of their own kind, although it 

 was known that they could mate with any other females. 

 This question had first to be settled by direct observation. 



Rudimentary winged females were isolated for three 



i Morgan, Zeit. f. indulct. Abs. und Vererb., VII, 1912. 



