CROSSING TWO HEMIPTEROUS SPECIES. 225 



Thus the type of intromittent organ characteristic of the species 

 is transmitted through the female to her male offspring, and also 

 directly by the male, and we may acid that this is further proved 

 by the back cross (Fi 9 X pure variolarius cf). Thus the mode 

 of transmission of this second exclusively male character is like 

 that of the genital spot both of these exclusively male characters 

 being transmitted through the female as well as directly from the 

 male neither of these characters therefore being sex-linked. 



Photos 13 to 20 show eight typical intromittent organs from the 

 F2 generation, these eight varying in length between 85 5 mm. and 

 140 mm. A few of these specimens (photos 13-15) show that 

 the factors which determine the genital spot and those which 

 determine the intromittent organ are not linked in inheritance 

 (see below). 



In our study of the transmission of the genital spot of vario- 

 larius (Foot and Strobell, '140) we divided the hybrids into three 

 groups those having a genital spot like that of pure variolarius, 

 those without a spot like servtts, and those with a spot inter- 

 mediate between these two extremes. In order to compare the 

 results from the study of the two exclusively male characters 

 the genital spot and the intromittent organ we have again 

 grouped the hybrids into three classes, those having a length 

 of intromittent organ like that of variolarius, those with a length 

 of organ like that of servtis, and those with a length intermediate 

 between these two extremes. 



By this grouping it is possible to compare the genital spot of 

 each individual hybrid with the type of intromittent organ of 

 the same hybrid, in order to determine whether these two 

 exclusively male characters are linked in inheritance to deter- 

 mine to what extent the two are associated in their transmission. 

 Before discussing this point we shall summarize the points of 

 agreement in the inheritance of the two characters. 



The intromittent organ like the genital spot is not sex- 

 linked, this being shown by the facts that it is transmitted 

 through the female, and also directly from the male to his male 

 offspring. The intromittent organ like the genital spot is 

 transmitted without the aid of either of the so-called "sex- 

 chromosomes." It is transmitted without the aid of the Y- 



