RESULTS OF CROSSING TWO HEMIPTEROUS SPECIES. 473 



Mendelism,j9i^i«s (1) the assumption of gametic purity, p/ws (2) the assumption 

 o£ factorial constancy," plus (3) the assumption of factorial multiplicity " 

 (Castle, '14 a). 



Results from backcross. Fi hybrid female (from E. variolarius ? 

 X E. servus c?) by pure E. variolarius male. 18 males, photos &2-&Q. 



This backcross was undertaken to obtain evidence as to whether the so- 

 called male- and female-producing spermatozoa differ in their function in the 

 transmission of the exclusively male character — the genital spot (Foot and 

 Strobell, '13 & '14). We shall briefly re-state this evidence here in order 

 to show that the original results are duplicated by the facts demonstrated in 

 this paper as to the method of transmission of a second exclusively male 

 character — the intromittent organ. 



First, the so-called male-producing spermatozoon can transmit the o-enital 

 spot. This was proved by the fact that the genital spot in the 18 males from 

 this backcross is inherited much more strongly from the pure variolarius male 

 than from the Fi hybrid males, and therefore this variolarius character was 

 transmitted directly from the male to its male offspring, and must, accordino- 

 to the hypothesis, have been transmitted by the male-producing spermatozoa *. 

 This evidence is repeated in the case of the intromittent organ, for the mean 

 length of the intromittent organ of these 18 males is 113"47mm., while the 

 mean length of the organ of the Fg generation is 124-42 mm. — the measure 

 therefore of the influence of the pure variolarius male in reducing the lenoth 

 of the intromittent organ ma}- be expressed as 10'95 mm. 



Second, this backcross demonstrated in the case of the genital spot that the 

 servus character — the absence of spot — was transmitted by the so-called 

 female-producing spermatozoon ; and this evidence of the transmission of an 

 exclusively male character by the female-producing spermatozoon is repeated 

 in the case of the intromittent organ, for the length of the intromittent organ 

 in these 18 males has been increased by the inheritance from servus. This is 

 demonstrated by the fact that the mean length of the intromittent organ of 

 the 18 males from this backcross is 113"47 mm., while that of the organ 

 of the Q2 pure variolarius males is 96"70 mm. The two servus characters — 

 absence of spot, and increased length of intromittent organ — must have been 

 transmitted (according to the hypothesis) by the so-called female-producing 

 spermatozoon of servus to the pure variolarius ? of the first cross, throuolj 

 which it was transmitted to her daughter, the F^ ? of this backcross. 



The demonstration that the so-called sex-determining spermatozoa do not 

 differ functionally in the transmission of such an exclusively male character 



* In making these deductions it is of course necessary to accept, for the sake of the 

 argument, the assumption of male- and female-producing spermatozoa, an assumption 

 which we belieA^e is still far from proved. 



LINN. JOURN. — ZOOLOGY, VOL. XXXII. 38 



