FERTILITY AND STERILITY IN DROSOPHILA 



207 



more offspring than their truncate brothers and sisters is borne 

 out by table 24, in which the F2 generation of the longs as thrown 

 by the truncates are tested in pairs. In this experiment they 

 gave an average of 92 offspring per pair, while 34 pairs of truncates 

 used for control gave an average of 47 offspring per pair. (Table 

 1, F45.) 



I have pointed out that the number of offspring produced by 

 a pair of flies is not an infallible guide to the fertilizing power of 

 their gametes. That the fertilizing power of the egg and sperm 

 of the long-winged forms is greater than that of the truncate flies 

 is supported by the foHowing experiment, in which the eggs were 

 isolated and 37 per cent hatched. Since I have never been able 

 to obtain more than 24 per cent of fertile eggs from the truncates 

 I conclude that this difference when taken in connection with the 

 other evidence is significant. Attention is called to No. 31, table 

 14b, in which the fertility of a long-winged female is 38 per cent, 

 or 14 per cent greater than her truncate sisters. 



The data recorded in table 25 are too small upon which to base 

 any very definite conclusion in regard to this obscure phenomenon, 



TABLE 23 



This table shows the result of testing in pairs the long-winged brothers and sisters of 



the truncates. For testing of truncate brothers and sisters to these, 



see table 1. — F 44- 



Sterile. 



