No. 578] DROSOPHILA AMPELOPHILA 



103 



were removed. One red and one pink of these females 

 were put into each of seven bottles. In this way the same 

 environmental conditions were secured for the eggs of 

 both. Five days later they were allowed to mate again 

 (not by the same males) and placed in a second set of 

 bottles. The same two females that were together in the 

 first set were also together in the second. There they 

 remained five more days. Counts of the flies that hatched 

 were made from day to day, and the bottles were emptied 

 as long as they continued to yield. The results are given 

 in Table V. 



The records of these flies show several interesting and 

 suggestive facts. It will be noted, in the first place, that 

 the length of larval life varies through wide limits. Each 

 bottle contained eggs which were deposited during a 

 period of no more than five days. The hatching periods, 

 however, extended through eleven days in the first set of 

 bottles (April 25-May 6) and twelve days in the second 

 set (April 30-May 12). The flies which emerged first 

 consumed but ten days for development; those which 

 emerged last took at least sixteen days. This phenom- 

 enon was more marked where the number produced was 

 larger, suggesting that crowding may retard the devel- 

 opment of some individuals. 



Of equal interest is the fact that the pink flies invariably 

 began to hatch from 24 to 48 hours later than the red. This 

 was true in the second set of bottles as well as in the first, 

 which proves that it was not due to late maturity of the 

 parents, for, at the time of transfer, they were in the 

 midst of their productive period. 



Another point of interest is to be found in the fact that 

 the pink stock was, on the whole, less fertile than the red. 

 In the two bottles V and ' g' where the productivity of the 

 two was about equal the red, like the pink, were also low- 

 producers. This is significant, and will be referred to 

 later. 



In order to test the above-mentioned facts, the follow- 

 ing experiment was performed. F a hybrids were mated 



