590 CALVIN B. BRIDGES 



this cross is red females and males. Of the factors concerned, 

 pink of the female is in the third chromosome and black of the 

 male is in the second chromosome. Both white and miniature are 

 in the sex chromosome at a distance from each other of approxi- 

 mately 32 units (Sturtevant, '13 a). The normal F] female, 

 then, is heterozygous for four factors, white, miniature, black, 

 and pink. The Fi male is heterozygous for black and pink, but 

 is normal with respect to white and miniature, since his only 

 sex chromosome came from his mother, who was neither white 

 nor miniature. I had three cultures of Fi and they produced 

 in aggregate the expected red females and males to the number 

 of 251 and 305 respectively. But I found also three white mini- 

 ature males, one in each culture. Their fathers were white and 

 miniature, but these were not Pi males left oyer in the culture, 

 because they were very young (young flies are very light in 

 body color and show other characteristic differences from the 

 adult), and occurred after I had emptied the culture bottles sev- 

 eral times. Fortunately I bred one of these males to virgin ^ 

 sisters, which were heterozygous for white, miniature, black, and 

 pink. The results showed conclusively that the male had really 

 come from the cross and was not the result of any contamina- 

 tion, in that it gave in the next generation all expected classes 

 from the cross of an Fi female by a white miniature male hetero- 

 zygous for black and pink, that is, there appeared blacks and 

 pinks, males and females, whites and miniatures, in all the com- 

 binations and permutations expected. 



Since my interest was centered primarily in the white and 

 pink characters, and I did not at that time realize the importance ' 

 of the problem, I counted the offspring of the non-disjunctional 

 male only with respect to white and pink, although the occur- 

 rence of blacks and miniatures of both sexes was noted. ^ The 

 count approximated expectation : (4:3:1:4:3:1"^. 



white 9 (4) red 9 (3) pink 9 (1) white cf (4) red cf (3) pink^9 (1) 

 106 93 30 111 78 30 



^ For comparison I give the Fg from normal males by sisters such as those to 

 which I mated the patroclinous male. 



red 9 (6) pink 9 (2) white c? (4) red c? (3) pink c? (1) 

 733 196 354 340 75 



