496 
Katharine Foot and E. C. Strobel! 
by a pure E. variolarius, we shoukl expect to liave a no more pronoun- 
ced spot in the offspring than we obtain by matings of two Fj hybrids. 
The facts, however, demonstrate that the spot is transmitted 
through the pure male E.variolariiis far more intensely 
than it is through the Fi male”. 
This is strikingly iUustrated by a comparison of the male offspring 
of an F 1 female and pure variolarius male t\*ith the 204 males tve have 
succeeded in raising from seven pairs of the F^ hybrids. "We have 18 
males from the former pair and the proportion with a strong variolarius 
spot is 14 out of the 18, whereas in F 2 generation the proportion is 18 
out of 204. Further, none of these 18 males from this back cross are 
without any spot, whereas 84 of the 204 males of the F 2 generation 
have no spot whatever. 
Our facts seem to have demonstrated two points: First, that the 
spot is inherited through the female without the aid of the Y chromo- 
some, and second, that the spot is inherited from the male without the 
aid of an X chromosome. IVe seem forced then to admit that in this case 
neither of the so-called sex chromosomes is necessary to the inheritance 
of an exclusively male character, the factors of which, it would seem, 
ought to be contained in a chromosome which determines sex, if, in fact, 
sex-determining chromosomes exist. The spot in E. variolarius is a part 
of the male genital segment and it is only logical to assunie that the fac- 
tors which produce it are associated with the factors which produce the 
male genital segment itself, wherever or whatever those factors are. As the 
facts do not seem to warrant the assumption that these factors are confined 
to either of the so-called sex chromosomes, we may re-examine them in the 
light of placing these factors in some other chromosome or chromosomes. 
As the so-called male-producing Spermatozoon of many forms has 
no Y” chromosome and therefore no male sex chi’omosome, it is obvious 
thai if this Spermatozoon is assumed to carry a factor which produces 
sex, this factor must be placed in some other cliromosonie, by those who 
bclieve that the chromosomes are the vehicles of such factors. Realizing 
this Mokgan (’ll) 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 scheine. 
Gametes of female — XAI — XM 
Gametes of male — XAI — M. 
A glance at text fig. 2 will show that placing the male factors in an 
homologous pair of chromosomes (in A and B of fig. 2 for example) ne- 
