THE DETERMIXATION OF SEX 333 



be of the homogametic sex while the other side would necessarily 

 be of the opposite sex, since it could not have more than one 

 allosome. 



Mosaic gynandromorphs in which the characters of the two 

 sexes are distributed at random through the body arc baffling. 

 The one valid conclusion to be derived from them is found in 

 McClung's statement that ''like other bodily functions ... sex 



Fig. 189. — A gynandromorph of PapUio turnus Linn. The left half of the 

 insect is of the normal yellow male sex while the right half is of the black 

 female form glaucus. (Through the courtesy of the Philadelphia Academy 

 of Sciences.) 



is a matter of cell activity, and must ultimately be explained in 

 terms of cell performance." 



The known facts concerning gynandromorphs have led to the 

 conclusion that in insects at least, the secondary sexual characters 

 are determined directly by genes. Any allosome, however, may 

 contribute definitely to the determination of either sex. The 

 chromosomal difference between the sexes is quantitative, as has 

 already been pointed out, unless we conclude that the y chromo- 

 some is an active determiner of sex and such a conclusion is not 



