No. 615] SHORTER ARTICLES AXD DISCUSSION 267 



The F 2 generation gave females all red and the males in equal 

 classes of red and white, which is the genetic behavior expected 

 for a sex-linked gene. To test whether this white was in the 

 same locus as the old white, a white male of this stoek was 

 crossed to a yellow-white female from the original stock. The 

 sons were yellow white and the daughters were white, not yellow, 

 since yellow is recessive and was not carried by the father. No 

 difference could be observed in eye color between either sex of 

 the new white, or the daughters compounded from the two 

 whites, and the males and females of the original white. It 

 seems reasonable to conclude then that the while gene has reap- 

 peared by a second mutation from the red gene. 



Second Origin of Gene for Rudimentary Wing 

 There appeared in a cross of an eosin miniature male to a 

 broad, vermilion, forked female (both from stock cultures, all 

 characters mentioned being sex linked) one son which was ver- 

 milion, forked like the mother, but which also had shortened 

 wings. This wing character was later shown to be rudimentary. 

 Crossovers in later generations showed that the maternal gene 

 for broad was also present, but its effect was obscured by the 

 rudimentary in all cases where both occurred together. This 

 male so obtained and bearing genes for broad, vermilion, rudi- 

 mentary and forked was outcrossed to a virgin wild type female 

 to test whether the new character was of a genetic nature. The 

 F, flies were normal in all respects. One pair of these produced 

 117 sons which were classified with respect to the characters ver- 



broad, which did show in certain crossovers where it was sepa- 

 rated from rudimentary. Out of 117 males. 3 were crossovers 

 between rudimentary and forked, which gave a percentage of 



Bridges 4 is 1.4 on the basis of a much larger number of flies. 

 There were 27 crossovers between rudimentary and vermilion, 

 which is a percentage of 22.2. while the above authors put it at 

 24.1. The nature of the crossovers obtained showed that the 

 gene for the wing character was between vermilion and forked, 

 which agrees with the assumption that it is a new appearance of 

 rudimentary. The crossover values obtained are sufficiently 

 near to expectation to justify this assumption in view of the 

 small number of flies. Crosses were made to the stock rudimen- 

 4 Carnegie Pub. Xo. 237, 1916. 



