CROSSING TWO HEMIPTEROUS SPECIES. 231 



ing and female-producing), but each of these groups can again 

 be separated into two types, in relation to their autosome content 

 one type containing the autosomes A, C, E, and the other type 

 the autosomes B, D, F. As we are discussing the transmission 

 of the testes, the factors for which are presumably carried by 

 the male-producing spermatozoa, we shall consider the two types 

 of these spermatozoa only those with A, C, E, Y, and those 

 with B, D, F, Y. 



Our problem, as stated above, is to determine whether it is 

 possible to place the factors which determine the testes of these 

 insects in one of the autosomes. 



A glance at text Fig. i shows that each of the autosomes is in 

 only half the male-producing spermatozoa, and is also in half 

 the female-producing spermatozoa. If, for example, we assume 

 that autosome A carries the factors for determining the testes, 

 and the X-chromosome carries the factors for determining the 

 ovaries, we shall have all the female-producing spermatozoa 

 carrying the factors for determining the ovaries, and in addition 

 to this, half of these spermatozoa will carry the factors for 

 determining the testes, as half of them have the A autosome. The 

 male-producing spermatozoa, on the contrary, will not only 

 carry none of the factors for determining the ovaries, but only 

 half of them can carry the factors for determining the testes, 

 as only half of them have the A autosome. 



These conclusions, forced by an analysis of the chromosomes, 

 are by no means in harmony with the demands of the chromo- 

 some sex-determination theory thus it is quite as impossible to 

 confine the factors for the testes to a single autosome, as we have 

 shown is the case with the other two exculsively male characters 

 the genital spot and the intromittent organ. We might avoid 

 this difficulty by assuming that the maturation divisions of one 

 pair of the autosomes is like that of the XY-chromosomes, and 

 that the factors for the testes are carried by one member of this 

 pair. This involves, however, the further assumption that this 

 autosome must follow the lead of the Y-chromosome or it might 

 arrive in the female-producing spermatozoon. Unless we are 

 willing to make some such unwarranted assumptions, it does not 

 seem possible to make the association between the testes and 



