266 CALVIN B. BRIDGES 



because of their favorable location in the chromosome. Purple 

 has an even higher interest because of its connection with the 

 development of several new fields in genetics and of principles 

 that are now made use of in every Drosophila experiment. 



ORIGIN 



In a stock which was supposed to be simply vestigial there 

 was found, February 20, 1912, a single male which had an eye 

 color much like that of the well-known double recessive ver- 

 milion pink. The color of the vermilion-pink eye is about that 

 of the pulp of an orange, and the early papers accordingly 

 referred to this double recessive as 'orange.' The new color 

 was seen to differ sHghtly from vermilion-pink in that it was of 

 a brilUant ruby-Uke transparency, and lacked the fiocculent or 

 slightly cloudy appearance of vermilion pink. This difference 

 seems to arise partly from a difference in the distribution of the 

 pigment. In vermilion pink the pigment looks as though it 

 were mainly in the spaces between the radially arranged om- 

 matidia with- a clearer zone just under the surface of the eye. 

 One sees in the vermilion pink eye a light fleck which travels 

 over the eye as it is turned. This seems to be due to a de- 

 ficiency of pigment in the deeper parts of the eye, and the light 

 fleck is this light center seen through the small group of facets 

 whose axes are in line with the eye. The pigment in the case of 

 the new eye color gave the appearance one would expect if it 

 were uniformly distributed or even in solution throughout the 

 eye. 



INHERITANCE 



This single male with the orange-like e3''e color was outcrossed 

 to a wild female, and in Fi gave only wild-type males and females 

 (wild-type 9 32, cf 33; reference no. Bl) which showed that 

 the color was recessive. In Fo the orange-like color reappeared, 

 but in addition the sex-linked eye color vermihon emerged, and 

 also a new eye color, 'purple,' which appeared equally among the 

 Fo females and males, and therefore was knoAvn to be an autoso- 

 mal (not sex-linked) character. It was now evident that the 



