RESULTS OF CROSSING TWO HEMIPTEROl's SPECIES. 



are the vehicles of such factors. Realizing this Morgan ('n) 

 concluded that "the factors for producing the male must be 

 located in some other chromosome" and he places these factors 

 in a pair of homologous chromosomes, as shown by his scheme. 



Gametes of female-- X M X M 

 Gametes of male - -X M M. 



A glance at text-fig. I will show that placing the male factors 

 in an homologous pair of chromosomes (in A and B of Fig. I for 

 example) necessitates their presence in all the spermatozoa of 

 both sexes, thus giving to the so-called female-producing sper- 

 matozoon the male-producing factors in addition to the female- 

 producing factors. The female-producing spermatozoon is 

 therefore heterozygous for sex and the male-producing sper- 

 matozoon homozygous for sex and this seems to involve a denial 

 of the assumption that has been the basis of so much experi- 

 mental analysis, namely, that the female is homozygous for sex. 

 How can the female be homozygous for sex when the so-called 

 female-producing spermatozoon has conveyed to her "the factors 

 for producing the male"? 



If we assume with Morgan that both members of a definite 

 diploid pair of chromosomes contain the factors for producing a 

 male, this must hold for the same diploid pair in both the female 

 and the male, and if the factors producing exclusively male 

 characters are linked with the factors for maleness, then each 

 member of this diploid pair should contain the factors for pro- 

 ducing the spot, which in E. variolarins is an exclusively male 

 character. 



As this diploid pair is in the female as well as in the male, it 

 would seem necessary to assume that in E. variolarius the female 

 carries an inhibitor of such exclusively male characters. But 

 one is embarrassed in considering where to place this inhibitor- 

 if we locate it in both members of an homologous pair of chromo- 

 somes, then it would be in the male as well as in the female. 

 If we place it in only one member of an homologous pair (in A t 

 for example, of text-fig, i), this would involve selective fertili- 

 zation, for if the female is fertilized by the so-called female- 

 producing spermatozoon that is without the A, and she has by 



