280 



CALVIN B. BRIDGES 



TABLE 51 



^ This table and the next (table 6) were included by Morgan in his paper on 

 "No crossing over in the male of Drosophila . . . .," Biol. Bull., April, 1914, 

 pp. 200 and 201. 



The question of crossing over in the male was the first point 

 attacked. Complementary Pi matings were made (June 13, 

 1913) by crossing purple vestigial to wild ('coupling') and by 

 crossing purple to vestigial ('repulsion'). Fi males from these 

 matings were back crossed singly to purple vestigial females 

 from the stock. The parents were in several cases transferred 

 at the end of ten days to fresh culture bottles and second broods 

 then raised. 



The offspring from the 'coupling' experiment (table 5, 5 pairs, 

 both broods) gave a total of 1071 flies, not one of which was a 

 crossover, and the 'repulsion' experiment (table 6, three pairs, 

 both broods) added 704 more (total 1775), not one of which was 

 a crossover. Since these were back-cross experiments, there was 

 no masking of results possible, and crossover gametes had every 

 opportunity to reveal themselves had any been formed. There- 

 fore, each fly recorded above is a true non-crossover. While the 

 total absence of crossovers in these repetitions of the male test 

 cannot prove that the apparent crossovers in the original test 

 were not genuine crossovers, it added to the already large body 

 of evidence which showed that they were aberrations from the 

 normal condition. 



