226 KATHARINE FOOT AND E. C. STROBELL. 



chromosome because it is inherited through the female, and it is 

 transmitted without the aid of the X-chromosome because it is 

 transmitted directly from the male to his male offspring. Like 

 the genital spot, the intromittent organ fails to show dominance 

 in the Fj. generation, and fails to show a simple Mendelian ratio 

 in the F 2 generation; but the details demonstrating these facts 

 must be reserved for our full report of this work, in which it will 

 be possible to compare the inheritance of these two exclusively 

 male characters in every individual of the FI and F 2 generations. 

 As in the case of the genital spot, we are forced to conclude 

 that if the factors determining the inheritance of the intromittent 

 organ are carried by definite chromosomes, they must be in 

 at least a pair of diploid chromosomes, and as in the case of the 

 genital spot, we are further forced to conclude that there are 

 factors in the cell, outside the chromosomes, which determine 

 just how many of the factors determining the character of 

 intromittent organ shall find expression in the first and second 

 generations of hybrids. The facts show, as in the case of the 

 genital spot, that this cannot be accomplished by the assumed 

 mechanism of division of the chromosomes, but is dependent 

 upon hypothetical factors outside the chromosomes, and thus 

 the distribution of unit factors through the mechanism of chromo- 

 some division seems to be an unnecessary assumption. If the 

 factors essential to produce these two exclusively male characters 

 are confined to one chromosome they can be in the Y-chromosome 

 alone, for according to the mechanism of the two maturation 

 divisions this is the only chromosome that can be in all the so- 

 called male-producing spermatozoa. The facts, however, demon- 

 strate that not only the genital spot, but the intromittent organ, 

 can be transmitted without the aid of the Y-chromosome. If, 

 as the facts demand, the factors for these two exclusively male 

 characters cannot be in less than a pair of chromosomes, there 

 seems no adequate reason for confining them to a single pair, 

 or even to the chromosomes at all, for if factors outside the 

 chromosomes and outside the mechanism of the division of the 

 chromosomes, are responsible for the exact expression or total 

 suppression of these characters, this deprives the chromosomes 

 of a most important function which has been attributed to them, 

 based on the mechanism of their division. 



