FERTILITY AND STERILITY IN DROSOPHILA 



361 



about 600. A comparison of tables 1 and 2 where the egg pro- 

 duction of the extracted truncates is given with table 3 and the 

 many tables in Part II where the total output of eggs of the 

 original truncates is represented will show that the above con- 

 clusion is warranted. 



TABLE 4 a 



Showing the result of breeding together 

 the extracted truncates. A9 X Ac? 

 (Fn truncates extracted from truncate 

 grandmother) 



TABLE 4 b 



1 



2 

 3 



4 

 6 



7 

 8 

 14 

 15 

 16 

 17 

 18 



TOTAL NO. OFFSPRING 



336 



295 

 408 

 330 

 364 

 no offspring 

 299 

 250 

 271 

 265 

 211 

 228 



B9 X Bd' {Fi truncates extracted 

 from truncate grandfather) 



FERTILITY OF THE EXTRACTED TRUNCATES BACK-CROSSED 



TO THEIR GRANDPARENTS, THE ORIGINAL TRUNCATE 



STOCK AND THE WOODS HOLE STOCK 



The foregoing pages have demonstrated the marked difference 

 in fprtiUty that exists between truncates and extracted truncates. 

 I wish here to consider the effects on fertiUty when the extracted 

 truncates are back-crossed to their low-producing grandparents 

 (truncates) and their high-producing grandparents (Woods Hole) . 

 I shall consider first the evidence that bears on the effect on. fer- 

 tility of back-crossing extracted truncates with truncates. This 

 experiment was carried out at the same time as experiment I in 

 this paper. The facts are recorded in table 5. 



