508 
Katharine Foot and E. C. Strobell 
calls for a satisfactory explanation by tliose ^Yho believe in sex-detcr- 
mining chromosomes, and oiir results cannot be cancelled by a dogmatic 
assertion that they liave no bearing on the subject. 
^loRGAX treats the facts with more consideration and attempts to 
give an explanation of them, tliough his explanation appears to ns more 
as an attempt to excuse the facts than to explain them. Part of his 
explanation is merely a restatement of oiir conclusions and the remainder 
is not in harmony with the facts. 
We concluded that our results demonstrate that the spot can be 
transmitted without the X or the Y chi'omosome and Morgan accepts 
this as follows, “these results may be explained on the assumption that 
the factors lie in other chromosomes than the sex-chronio- 
somes”. 
"We concluded that if one assumes (for the sake of the argument) 
that the spot factors are in a diploid pair of chromosomes, it becomes 
necessary to assume other factors outside the chromosomes. called 
such hypothetical factors ‘‘inhibiting factors” and we said of them — 
“We are forced to aclniit that inhibiting factors — whatever they are — 
must be located outside the chromosomes — in the region of pure hypo- 
thesis.” 
Morgan appears to accept this, calling such hypothetical factors 
“things in the cell”, and symbolizing them as A.B.C. He says “the 
result (or character) that a factor produces depends on its relation to 
other things in the cell, (here A.B.C.)” and he adds, “We are dealing, 
then, not with the relation of X to S alone, but this relation in turn 
depends on the proportion of both X and S to A.B.C.” 
In the above quoted paragraph he includes in his explanation the 
assumption of a relation between the spot factors and the X chromosome 
and this we believe is a part of his explanation which is not sustained 
by the facts. The spot can be transmitted directly front the male to 
his male offspring — and therefore this must be by the male-producing 
Spermatozoon — (if there is such a thing) and the so-called male-pro- 
ducing Spermatozoon has no X chromosome. It is impossible to believe 
that in such cases the inheritance of the spot is depcndent upon the 
relation of the spot factors of the sperm to the X clmomosome in the 
egg, especially if the cross is made with a pure semis egg. Morgan 
evidently thinks this is possible, however, for in his explanatory diagram 
he illustrates a cross between E. serms $ x £. variolarnis (J, a cross 
which we explaiiied we were unable to attempt on account of scarcity 
of material. 
