No. 642] VARIATION IN SEX CHARACTERS 63 



intersexes result from an intermediate ratio of X to auto- 

 somes because the X has a net female tendency, then it 

 might be expected that by increasing the ratio of X to 

 autosomes a superfemale would be produced, and con- 

 versely, a supermale by increasing the relative number of 



autosomes. Diploid individuals with an extra X-chromo- 

 some (2n plus X) have now been identified among the 

 progeny of certain strains of high non-disjunction, among 

 the offspring of triploid females and elsewhere. These 

 flies resemble females ])ut are very inviable and form a 

 distinct character tvpe. They are sterile and sections of 

 the gonads show abnormal ovarios. These differences 

 all result from the unbalance within the X, and are there- 

 fore of the sexual-sex-limited category. That these dif- 

 ferences are not greater is partly due to the same high 

 internal balance of the X that we met with in analysing 

 males and intersexes, and is partly to be explained on the 

 ground that for many of the characters the overbalance 

 is not vet great enough to pass a second critical point. 



Conversely, individuals with one X-chromosome and 

 an extra set of autosomes have been identified among the 

 offspring of triploid females. These are males distmctly 

 different from normal males and sterile. 



If there were time, it would be interesting to supple- 

 ment and inodil'v tin- view jnst prcsi ntcd l)y comparisons 

 ,,.;^iwV,. ,»".t,„-iMl< rUrxvhwiK nn.l ix'fhaps to specu- 



