132 C. L. TURNER. 



A. PRELIMINARY EXPERIMENTS. 



Using the white-eyed and brown-eyed specimens with unknown 

 genetic constitution from the mass culture preliminary crosses 

 were made for the purpose of getting some information as to the 

 heritability and possibly the method of inheritance of the mutation 

 in case it proved to be heritable. 



a. White-eyed by White-eyed Crosses. 



Sixteen crosses of white-eyed by white-eyed specimens were 

 made, the specimens being isolated at the time of their emergence 

 to insure virgin stock. From all these crosses 731 individuals 

 were obtained and all were white-eyed. The eyes and Mal- 

 pighian tubules of all showed a total lack of pigmentation. The 

 question as to the heritability of the mutation w r as thus answered 

 while the completeness and the permanence of the mutation has 

 subsequently been established by maintaining pure strains of 

 white-eyed flies up to the present time. 



b. Brown- eyed by Brown-eyed Crosses. 



Brown-eyed flies were isolated from the mass culture in a very 

 young stage and 163 crosses were made, 91 of which were suc- 

 cessful. In some cases all of the resulting progeny were brown- 

 eyed. For example, culture number 138 produced three brown- 

 eyed males on the ninth day, fifty-three more on the tenth day 

 and during the following four days twenty-two brown-eyed males 

 and forty-seven brown-eyed females. 



In a few cultures some white-eyed specimens appeared. All 

 such cultures showed a comparatively large number of brown- 

 eyed specimens but the ratio was variable. It was important, 

 however, to have obtained while-eyed specimens from a brown- 

 eyed by brown-eyed cross since it indicated that the brown-eyed 

 condition was probably dominant and the white-eyed condition 



recessive. 



c. Brown-eyed by White-eyed Crosses. 



Twenty-eight matings were made using brown-eyed males and 

 white-eyed females and twenty-four using brown-eyed females 

 and white-eyed males. Both types of crosses produced the same 

 result thus demonstrating that there was no sex linkage. Of 

 these matings thirty-two were successful. In six lots of progeny 



