No. 644] MUTANT CHARACTERS IN DROSOPHILA 221 



be heterozygous for the new factor, and it was found 

 that the character was also present in males in sister 

 cultures which had been used for stocks. 



Yelloiv {y) 



Description. -^In " yellow " flies the body, wings and 

 legs are deep yellow. The bristles and hairs are all yel- 

 lowish or bronze instead of black. In the latter respect 

 yellow differs from the yellow in Drosophila virilis which 

 has black or dark brown bristles and hairs. 



Origin. — A single yellow male appeared in a bottle of 

 scute rough stump stock. 



Yellow was found after the main part of this paper 

 was prepared for publication, and since the experiments 

 involving it have not added materially to the data given 

 in the tables they are omitted from the latter and are 

 given briefly here. 



The original yellow scute rough stump male was mated 

 to normal females giving a normal F^. The latter, inbred 

 in pairs, gave 1354 normal daughters and the following 

 classes of sons: normal 488; yellow scute rough stump 

 466 (non-crossovers 954) ; yellow scute 25, rough stump 

 23 (single crossovers in region two 48); yellow scute 

 rough 49, stump 46 (single crossovers in region three 95) ; 

 yellow scute stump 3, rough 2 (double crossovers involv- 

 ing regions two and three, 5). In addition, two yellow 

 rough stump males and one yellow stump male were ob- 

 tained. Of the former, one proved to be genetically scute 

 when tested and hence should be in the non-crossover 

 class. The other gave no progeny, but presumably was 

 also a non-crossover. The third fly likewise failed to 

 breed, but since it lacked rough as well as scute it pre- 

 sumably represents a double crossover in regions one and 

 three. It is this fact which leads to the tentative location 

 of yellow above rather than below scute on the map." 



* This is supported by subsequent data. 



