LINKAGE OF THE FACTOR FOR BIFID \VIXG. THE 

 BIFID \VIXG AND OTHER SEN-LINKED 

 FACTORS IN DROSOPHILA. 



ROBERT CHAMBERS, JR. 



The experiments described in the following pages were made 

 primarily in order to test whether crossing-over of factors has 

 any subsequent effect on the linkage relations of the factors 

 involved. For instance, if a red eyed fly with bifid wings is 

 crossed to a white eyed fly with normal wings there will appear 

 in Fo the non-crossover classes, red bifid and white normal, 

 and also some crossovers white bifid and red normal. These 

 cross-overs (white bifid) were then used to determine whether 

 the same linkage values would reappear in their grandchildren; 

 in other words, whether a crossover in a particular place pre- 

 disposes to more frequent crossing-over in the same place. 



I wish to take this opportunity of acknowledging my indebted- 

 ness to Professor Morgan and to Mr. Bridges for their advice 

 and suggestions. 



The term "bifid" was given to a type of wing in which the 

 second inner vein fails to reach the margin, often producing a 

 bifid or forked wing. 1 The forked condition is variable. A 

 constant feature, however, which the forked condition frequently 

 accompanies, is a fusing of the wing veins at the base of the wing. 

 Flies possessing this characteristic cannot fly. 



The following abbreviations are used in the tables to denote 

 the factors taken account of in the flies studied: 



For eye color R = red, V = vermilion, W = white; 



For body color Gr = Gray, Y yellow ; 



For wing shape L = : long, Bf = bifid; 



N = factor to which sex linked factors are linked; 



= gamete not possessing X-factor. 



The factors R, V, Gr and Bf are in association with the X-factor 

 which is duplex in the female and simplex in the male. 



1 Morgan, Science, Vol. 35, March 12, 1912. 



