230 SABRA COLBY TICE. 



Pi VERMILION NARROW BARRED 9 (HoMOZYGOUs) BY VERMILION BARRED d*. 

 FI Vermilion Barred $. Vermilion Barred cf. 



246 67 72 



247 30 39 



248 52 46 

 250 42 37 



253 43 50 



254 48 46 



Total 282 290 



VIABILITY. 



In the foregoing experiment where an equality of barred and 

 normal was expected, it is evident that the mutant character is 

 almost as viable as the normal. For this reason it should prove 

 valuable for further work on linkage. In the experiments in 

 which no linkage is involved, there are 4,671 barred among 

 9,578 flies. The percentage of barred is 48.7 where 50 is ex- 

 pected. Where the experiments involving linkage are included, 

 the barred flies total 9,767 out of 20,240 and the percentage is 

 zi 8. 2. The relative viability of white and barred appears in 

 those experiments in which both were raised under the same 

 conditions as 45.4 per cent, to 49.9 per cent. The relative 

 viability of vermilion and barred was 51.7 per cent, to 46.8 per 

 cent. 



CONCLUSION. 



Barred eye a new sex-linked character appeared in Droso- 

 phila in a single red-eyed male fly and its dominance is constant 

 over the normal eye. The broad bar of the heterozygous 

 females distinguishes them from the homozygous ones w y ith a 

 narrow bar. The viability of the stock makes it valuable for 

 linkage experiments. 



By taking the percentage of cross overs as an indication of 

 distance on the chromosome, we can place the factor for barred 

 approximately at 56. 



ZOOLOGICAL LABORATORY COLUMBIA LTNIVERSITY, 

 October, 1913. 



