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THE AMERICAN NATURALIST [Vol. XLIX 



Evidently then the rudimentary females had been fertil- 

 ized by a long-winged brother before isolation, as well as 

 by the rudimentary male later. No offspring were pro- 

 duced by a third mating, to bar males. 



A third and similar experiment was made. Of twelve 

 females, none gave any rudimentary offspring, two gave 

 three bar daughters apiece, but no rudimentary sons. 



In a fourth experiment thirteen rudimentary- winged 

 females were isolated from stock. They were not neces- 

 sarily virgins. One gave a rudimentary- winged son ; an- 

 other gave two rudimentary daughters and six such sons. 



If only a single pair of flies is present in a culture and 

 few or no larva) are produced, the banana generally decays 

 instead of fermenting. It might happen under these con- 

 ditions that the few larva; from rudimentary females 

 might fail to develop, and the rudimentary sons might 

 also suffer, even when some of their long-winged sisters 

 (the father being a normal male) succeed in developing. 

 To make conditions favorable in this respect I proceeded 

 as follows: A red-eyed rudimentary female was kept at 

 first with a red-eyed rudimentary male for three or four 

 days. Then a few old white bar females and males were 

 added and fresh food given. The presence of these flies 

 and their progeny would serve to keep the food in good 

 condition. Moreover if the rudimentary female had been 

 fertilized by the rudimentary male she would produce ru- 

 dimentary daughters and sons. If she were subsequently 

 fertilized by the white bar males she would also give red 

 (heretozygous) barred daughters, but these could not be 

 distinguished from the daughters that the white-bar fe- 

 male would give were she fertilized by the red rudimentary 

 males. Nevertheless all of the sons of a rudimentary fe- 

 male would be rudimentary round-eyed males, regardless 

 as to which male was their father, and their presence 

 would show to what extent the rudimentary females were 

 fertile. The experiment was varied and simplified by 

 removing the rudimentary males, when the white bar 

 males and females were added. 



