244 



Sturtevant. 



obtained. In fact, its absence furnishes another confirmation of the 

 general conceptions advanced in this paper. That trijjle crossing over 

 is possible, however, appears from the fact that one was obtained in 

 an experiment involving W, M, E and a fourth locus (containing the 

 gene for bifid mngs — see Morgan '12 f) between W and M'). 



Table V. 



"i_r 



"LTL 



Total 



numbers 

 percent 



1010 

 65-0 



13 

 0- 



460 

 29-6 



58 

 3-7 



1 

 0-1 



0-1 



10 

 0-6 





 0-0 



1554 



Chromosome 11: Single Crossing Over. 



The existence of linkage between two non-sex-liuked pairs of genes 

 in Drosophila was reported by Morgan and Lynch ('12), and it was 

 pointed out that, on the chromosome view, these genes must be considered 

 as lying in one of the autosomes. Further data on this case have been 

 published by Morgan ('12 d), and Sturtevant and Bridges ('14) have 

 reported another gene in the same chromosome. I shall consider these 

 three genes in this paper, and also two others which lie in the second 

 chromosome. The five loci, in the order of their positions in the chromo- 

 some, are as follows: 



B (black). The bb flies have black body color. The mutant was 

 first recorded by Morgan ('lid), and the gene was one of the two 

 first shown by Morgan and Lynch ('12) to lie in chromosome n. Its 

 linkage has also been discussed by Morgan ('12 d) and by Sturtevant 

 and Bridges ('14). 



Vg (vestigial). The vgyg flies have vestigial wings. The mutant 

 was described and the linkage of the gene reported by Morgan and 

 Lynch ('12). Linkage also discussed by Morgan ('12d). 



Cv (curved). The cvcv flies have curved wings. Mutant described 

 briefly and linkage of the gene reported by Sturtevant and Bridges ('14). 



Ba (balloon). The baba fHes have balloon wings. Mutant described 

 by Morgan ('lid). 



^) This case was mentioned in a footnote to my earlier paper ('13a, p. 52). Tiie 

 note was written hurriedly, and at a time when our system of nomenclature had just 

 been changed, so that I inadvertently stated that it occurred within the distance WM 

 (on the nomenclature used here) iustead of the distance WR, as it should have been. 



