FERTILITY AND STERILITY' IN DROSOPHILA 



367 



Diagram H Showing the fertility of the extracted longs when mated together 

 and when crossed with each" other. 



crossed to the truncate male; and that in the reciprocal cross 

 there is shown not only no rise in fertility but an actual in- 

 compatibility (diagrams A and B). 



It has been shown that the fertility of the truncates is raised 

 from about 25 per cent to 50 per cent by crossing out to a wild 

 stock and extracting. It must be remembered, that the fertility 

 of the wild stock from which the truncates were extracted was far 

 below 100 per cent. It seems altogether probable that had a more 

 fertile stock been used the fertility of the extracted truncates 

 would have been still higher. 



FERTILITY OF THE LONG-WINGED BROTHERS AND SISTERS 

 OF THE EXTRACTED TRUNCATES 



The question still remains as to how the long-winged brothers 

 and sisters of the extracted truncates behave in respect to fertility 

 when tested together. The data recorded shown in table 7 gives 

 an answer to the question. 



The results of this experiment as expressed in diagram H show 

 that the long-winged brothers and sisters of the extracted trun- 

 cates are more fertile than the extracted truncates (in this case 

 by over 25 per cent). It would seem from this that while it is 

 possible to put a certain amount of fertility into the gametes of 

 the truncates, yet a certain degree of incompatibility remains 

 with the truncate wing as evidenced by the fact that their long- 

 winged brothers and sisters give a higher degree of fertility. It 

 is to be noticed in this case that there is no rise in fertility on 

 crossing. The fertility in the crosses is practically the same as in 

 the controls. 



