LINKAGE VARIATION IN DROSOPHILA 



11 



TABLE 12 

 Cases oj change of linkage in the second chromosome, from, tables 1, 2, 5, 6, 7 and 11 



TABLE 13 



Change for each linked pair of gens 



PURPLE 

 VESTIGIAL 



Decrease. 

 Increase. 



13 

 1 



PURPLE 

 CURVED 



STREAK I 

 MORULA ! 



Percentage of decrease 32.3 



12.7 



22.2 



10 



21.5 



1 







10.1 



49 

 11 



cases of decrease and of increase for each pair is shown (table 13). 

 The percentages of crossing-over calculated from the totals 

 of the first broods and of the second broods for each pair of gens, 

 have shown in every case a fall which is considerable in amount. 

 Table 13 (last line) gives this decrease in amount calculated as 

 a percentage fall from the value given by the first broods as a 

 standard, as was done in tables 4 and 8. All of these methods 

 show the same real change in the amount of crossing-over 

 between second chromosome gens in the second brood as com- 

 pared with the first brood from the same female. 



THE SEX CHROMOSOME DATA 



Although in the case of the first, or sex chromosome, the data 

 are not as great in amount as for the second, the conclusion 

 is quite certain that here there is no change in the amount of 

 crossing-over with second broods (table 14). 



Between vermilion and fused ('fused' is at the extreme right 

 end of the known plotted chromosome) there is a large amount 

 of crossing-over, and the totals show that the value for the 

 second broods is practically identical \vith that of the firsts. 

 The five females tested showed a faU in three cases, balanced by 



