Sex Dctcrwiuation iqq 



fundamental facts in dilYcrcnt tcnns or by the use of 

 different indices; (3) the chiim that both are true hut 

 cover different territories, that one of tJiem cxphiins 

 certain types of cases and the other explains other t>'])cs 

 of cases. 



Until very recently the tJiird alternative seemed the 

 most acceptable, inasmuch as the two t\7)es of sex deter- 

 mining mechanism had never been clearly identiticd in 

 the same organism. The recent work of Hkiugk.s (6, 7), 

 however, sways opinion to the second of the foregoing 

 alternatives, for it harmonizes the two contradictory 

 views on sex determination to a degree that would hardly 

 have seemed possible. 



An unexpected distribution in inheritance of known 

 factors, which are located on the second and third chro- 

 mosomes of the fruit fly, was explainable on the assump- 

 tion that the female parent was triploid with respect to 

 these chromosomes. Cytological examination proved 

 that this was actually the case. The same grouj) of 

 flies also exhibited some remarkable irregularities in 

 their sex condition. A considerable group of intersexes 

 occurred, as evidenced by the secondary sex characters 

 and the condition of the gonads as well. (This was 

 apparently a bimodal group , some of the intersexes being 

 of a more '^female" t>pe and others of a more "male" 

 t}T3e.) Cytological examination of these indi\iduals 

 revealed that the second and third chromosomes were 

 regularly present in a triploid condition, that the fourth 

 chromosome was either diploid or tri])loitI, and that two 

 X chromosomes were regularly present (witJi or without 

 a Y chromosome). The situation is interpreted as 

 follows : 



