FERTILITY AND STERILITY IN DROSOPHILA 



153 



females were capable of transmitting the defect. The control 

 shows that family No. 151 of the inbred stock was the least 

 affected, and it is to be noted that sterility reappears among the 

 grandchildren of this family in less intensity than among the 

 grandchildren of the other two families. This fact seems to 

 indicate that the intensity to which the sterility reappears in the 

 F2 generation bears a causal relation to the intensity in which it 

 entered the cross. 



Crosses between inbred, truncate and Woods Hole stock 



In the sixth generation of the inbred stock, when the sterility 

 of the females appeared in its greatest intensity (50 per cent; 

 table 2), crosses were made with the Woods Hole stock and also 

 with the truncate stock. The truncate stock was also crossed 

 with the Woods Hole stock, and since the truncate stock at this 

 time was a relatively fertile stock, it serves as an excellent control 

 for the female sterility of the inbred stock. This experiment 

 then consisted of three crosses, together with their reciprocals 

 and controls: (1) The inbred stock by the Woods Hole stock; 

 (2) The inbred stock by the truncate stock; (3) The truncate 

 stock by the Woods Hole stock. 



The control on the Woods Hole stock used in this experiment 

 shows that one sterile male occurred in 58 pairs (table 12, Lot A). 



TABLE 14 a 



Crosses between the inbred stock and the Woods Hole stock, showing the behavior of 

 sterility in the Fi and F^ generations. Woods Hole 9 X inbred cf No. SI 



* Sterile cf 



