192 KATHARINE FOOT AND E. C STROBELL. 



If, as stated above, we attempt to locate the spot factors in 

 the X chromosomes, we cannot expect these factors to be trans- 

 mitted through the male producing spermatozoon and therefore 

 if an FI female hybrid is fertilized by a pure E. variolarius, we 

 should expect to have a no more pronounced spot in the off- 

 spring than we obtain by matings of two FI hybrids. The facts, 

 however, demonstrate that the spot is transmitted through the pure 

 male E. variolarius far more intensely than it is through the F\ male. 



This is strikingly illustrated by a comparison of the male 

 offspring of an FI female and pure male variolarius with the 191 

 males we have succeeded in raising from seven pairs of the FI 

 hybrids. We have 18 males from the former pair and many 

 of them have the genital spot stronger than any of the 191 

 males from the F! parents. Further, none of these 18 males are 

 without any spot, whereas 84 of the 191 males of the F z generation 

 have no spot whatever. 



Our facts seem to have demonstrated two points: First, that 

 the spot is inherited through the female without the aid of the 

 Y chromosome, and second, that the spot is inherited through 

 the male without the aid of an X chromosome. We seem forced 

 then to admit that in this case neither of the so-called sex chromo- 

 somes is necessary to the inheritance of an exclusively male 

 character, the factors of which, it would seem, ought to be 

 contained in a chromosome which determines sex, if, in fact, 

 sex determining chromosomes exist. The spot in E. variolarius 

 is a part of the male genital segment and it is only logical 

 to assume that the factors which produce it are associated with 

 the factors which produce the male genital segment itself, 

 wherever or whatever those factors are. As the facts do not 

 seem to warrant the assumption that these factors are confined 

 to either of the so-called sex-chromosomes, we may re-examine 

 them in the light of placing these factors in some other chromo- 

 some or chromosomes. 



As the so-called male-producing spermatozoon of many forms 

 has no Y chromosome and therefore no male sex-chromosome, 

 it is obvious that if this spermatozoon is assumed to carry a 

 factor which produces sex, this factor must be placed in some 

 other chromosome, by those who believe that the chromosomes 



