10 



CALVIN B. BRIDGES 



'repulsion' experiments. The data presented in this paper 

 bring this total up to 11,353 flies and make the amounts for 

 'coupling' and 'repulsion' almost exactly equal, as shown in table 

 10. 



TABLE 10 

 Ldnkage of black and curved {Ists) with balanced viability 



The last case on which I can now present data for the second 

 chromosopie is that of streak and morula. Streak is a domin- 

 ant mutation which occupies a chromosome position far from 

 black in the opposite direction (left) from the loci occupied by 

 the other mutants so far treated. Morula occupies a locus 

 likewise veiy far from black but in the opposite direction (to 

 the right) so that a great section of the chromosome extending 

 beyond the black curved section in both directions is tested b}^ 

 this experiment. Here also the single case so far tested showed 

 a fall (table 11). 



TABLE 11 

 Pi streak 9 X morula <f . B.C. Fi streak ? X morula (^ d* 



NON-CROSS- 

 OVERS 



CHOSSOVEBB 



1 Streak 



Morula 



I Streak- 

 I morula 



Wild 

 type 



82 

 82' 



50 

 50 



47 

 31 



40 

 26 



31 



24 



I PER CENT OF 

 I CROSSOVERS 



168 

 131 



42.3 



38.1 



-4.2 



In table 12, I have summarized by tables the cases for the 

 second chromosome. Of the sixty tests, forty-nine showed a 

 decrease from first to second broods. This decrease appeared 

 uniformly in each experiment. 



A more satisfactory method of summarizing the data is that 

 of table 13, wherein the data have been collected according 

 to the hnked pair of gens tested. The relative number of 



