FERTILITY AND STERILITY IN DROSOPHILA 191 



known in the beginning much labor could have been saved by 

 picking the eggs from mass cultures, although this would give 

 little insight into the total output of eggs from a single female. 

 The former plan allows us to get much closer to the problem in 

 hand. The results of Experiment IV are given in diagram C. 



Woods K ^WoodiK 



^ i'Tio eqqs iiolaiaoL. 



h- 7Vo etjqs haicheai 



Diagram C Effect on fertility of crossing truncate and Woods Hole stocks; 

 from table 15. 



This experiment served in a preliminary way to show that the 

 egg-picking process could be relied upon in general as it gives 

 results in harmony with the earlier breeding experiments. The 

 evidence seems to show conclusively that only one egg in four or 

 five of the truncate female, when fertilized by its own male, will 

 complete development. Moreover, it is shown that the Woods 

 Hole male can fertilize more than twice as many of the truncate 

 eggs than can her own male although it has been shown in earlier 

 experiments that he produces an abundance of fertile sperm. It 

 is interesting to note that only 77 per cent of the eggs of the 

 Woods Hole stock hatched. It was the expectation that this stock 

 would show a fertility of something like 100 per cent. At first 

 I was inclined to believe that this discrepancy was due to some 

 defect in the egg picking process itself, but the results of later 

 experiments together with the behavior of this stock does not 

 bear out any such conclusion. Since these experiments were 

 completed I have obtained a fertility of 96 per cent with two new 

 wild stocks. 



It seemed to me that the explanation for the low production of 

 the truncates was not far to seek. That the length of life is a 

 factor is not to be doubted, but more than that it is evident from 



