No. 580] 



INFERTILITY OF DROSOPHILA 



2-4.". 



four males that fall into these two classes. There is one 

 female in the second table, that is red, long, round. She 

 must have resulted from a cross-over gamete, a long, 

 round egg being fertilized by a female producing sperm 

 of the rudimentary male. 



Still another experiment like the last one was made, but 

 vermilion-eyed flies instead of bar-eyed flies were added. 

 The virgin rudimentary females that were used were not 

 allowed to mate first (as before) with rudimentary males, 

 in order to meet a possible objection to the preceding ex- 

 periment, namely that the sperm athecse, if first filled with 

 sperm from the rudimentary males, might be incapable of 

 filling again with sperm when another male of a different 

 stock is added. The vermilion (long-winged males) would 

 give, with their own females, flies with vermilion eyes, 

 while the vermilion males that mated with the rudimen- 

 tary females should give red-eyed, long-winged females 

 and rudimentary red-eyed males. In the following table 

 the number of rudimentary females tested in each culture 

 is given in the top line ; in the second, central, line the 



square above ; and in the lowest line a record of the num- 

 ber of vermilion offspring given by the flies in the culture 

 under observation. 



only nine red-eyed daughters were produced (if we ex- 

 clude one culture in which five red long females and three 

 red-eyed males appeared which must be due to error or to 

 contamination). Of the nine offspring seven came from 

 one culture, and possibly from one female in that culture 

 that laid an exceptionally high number of eggs. The 

 complete absence of rudimentary males may be explained 



