234 



THE SECOND-CHROMOSOME GROUP 



ments, which should be the case to secure the most perfect balancing of 

 the inviability (tables 80, 81, 82, and 83). 



The grand totals for these four complementary back-cross experi- 

 ments furnished 6,794 flies, of which 3,469 were non-cross-overs, 2,791 

 cross-overs between black and arc, 374 cross-overs between arc and 



TABLE 81. PI, black arc morula cf X wild 9 ; B.C., 

 black arc morula cf of stock. 



wild-type 9 X 



TABLE 82. PI, black morula d" X arc 9 ; B.C., 



arc morula cf of stock. 



wild-type 9 X black 



TABLE 83. PI, black 9 X arc morula d"; B.C., 

 arc morula cf , from stock. 



wild-type 9 X black 



