592 CALVIN B. BRIDGES 



nally derived carried white and the paternally derived carried 

 eosin. The peculiarity of this combination in the female is that 

 in color it looks like an intermediate between white and eosin, 

 hence the name white-eosin compound. Several cultures of the 

 type described above produced in aggregate 2073 white-eosin 

 compound pink females heterozygous for vermilion, and 2037 

 white pink males. But in addition there were nine white females 

 and two males of a grade of color corresponding to eosin ver- 

 milion pink, that is, to the color of the fathers. These two 

 males were sterile so I could not test the correctness of my 

 classification. 



With the matroclinous females however, I made the following 

 tests. One of them I mated to her white brothers, and in the 

 next generation got 51 white females and 60 white males. This 

 test only shows that my classification of the female as white was 

 correct, for she gave no eosin sons, as did her ordinary sisters 

 mated to the same males. 



Another of these white females I mated to a double recessive 

 male, namely vermilion pink. All the ordinary sisters were 

 heterozygous for vermilion, but if my hypothesis is correct, then 

 the non-disjunctional female should be the exact counterpart of 

 her mother not only in being white, (as the first test showed she 

 was), but also in being pure for not-vermilion, although her 

 father was vermilion. If she were heterozygous for vermilion, 

 it would show in that half of her sons and daughters would be 

 vermilion. As a matter of fact none of her daughters were ver- 

 milion and all of her sons were white, with one exception. She 

 was, then, the exact counterpart of her mother as far as all sex 

 chromosomal characters were concerned. The one exception, a 

 vermilion pink male, was likewise an exact counterpart of his 

 father. The actual offspring of the second white female by the 

 vermilion pink male of unrelated stock were: 



white (pink) 9 pink 9 white (pink) cT verm, (pink) d' 

 2 52 54 1 



All the flies are pink because pink entered from both sides. 

 The presence of the one vermilion pink male and the two white 



