NEW DATA. 



35 



The Fi males were sable like their mother. The evidence thus shows 

 that sable is a sex-Hnked recessive character. Our next step was to 

 determine the linkage relations of sable to certain other sex-linked 

 gens, namely, yellow, eosin, cherry, vermilion, miniature, and bar. 



Table 6. — Pi wild 9 9 X sable cf . Fi tvild-type 9 9 X Fi zuild-type cf & . 



' Wherever reference numbers are given, these denote the 

 pages in the note-books of Bridges upon which the original 

 entries for each culture are to be found. 



Table 7. — Pi sable 9 X wild cf cT. Fi wild-type 9 X Fi sable & 



LINKAGE OF YELLOW AND SABLE. 



The factor for yellow body-color lies at one end of the known series 

 of sex-linked gens. As already stated, we speak of this end as the left 

 end of the diagram, and yellow as the zero in locating factors. 



When yellow (not-sable) females were mated to (not-yellow) sable 

 males they gave wild-type (gray) daughters and yellow sons. These 

 inbred gave in F2 two classes of females, namely, yellow and gray, and 

 four classes of males, namely, yellow and sable (non-cross-overs), wild 

 type, and the double recessive yellow sable (cross-overs). From off- 

 spring (F3) of the F2 yellow sable males by F2 yellow females, pure stock 

 of the double recessive yellow sable was made up and used in the 

 crosses to test linkage. 



In color the yeltow sable is quite similar to yellow black, that is, a 

 rich brown with a very dark brown trident pattern on the thorax. 

 Yellow sable is easier to distinguish from yellow than is yellow black, 

 even when the flies have not yet acquired their adult body-color. 



Yellow sable males were bred to wild females and Fi consisted of 

 wild-type males and females. These inbred gave the results shown in 

 table 8. 



