NON-DISJUNCTION OF SEX CHROMOSOMES 597 



I continued tests of this line of females for three generations 

 •more as follows: From the fifteen non-disjunctional females I 

 selected three which I mated to four red brothers. If both the 

 females and males were heterozygous for pink I should get pink 

 females among the offspring and these in fact I found as follows : 



14 257 46 307 17 



*In addition to these red males there was a red eyed lateral gynandromorph, 

 which is being figured by Morgan in "Heredity and Sex." 



From among these fourteen matroclinous white females I mated 

 two to four of their red brothers. The results were: 



It is quite probable that only one of these flies was heterozygous 

 for pink, since theoretically, only half of the fourteen flies should 

 be heterozygous for pink. For they came from a cross of hetero- 

 zygous non-disjunctional female to a wild male (not-pink). 

 The five cases like the last sum up to: 



Expectation calls for fifteen red to seven pink among the ex- 

 ceptional males. I think that probably the non-appearance of 

 the pink males has no significance. 



Three more of the fourteen white females I now mated to red 

 males of wild stock. The results were 



19 230 175 



From the nineteen exceptional white females here produced, 

 I mated three to wild males and obtained : 



