oue C2 (CLT PPLE 
contributed by the gametes which formed it, or these complexes 
separately.. The implant, on the other hand, is always treated 
as a combination of the factor complexes which it possesses, 
and has a single individuality differential which is the result of 
such a combination of complexes. 
The bearing of these matters upon the results with the tumor 
J.W.B. in the series here reported upon is found in the fact 
that the data given for the common race (N) shows that some 
of the factors contributing to the individuality differentials of 
the females are developed more clearly and begin to function 
with the onset of sexual maturity and its accompanying dif- 
ferentiation. Embryonic tissue or the tissue of the new-born 
may be supposed to have an individuality differential which is 
less clearly and distinctly defined, and which is simpler than 
that of the tissue of older animals. It discriminates less actively, 
therefore, against the individuality differential of the bit of im- 
planted tumor tissue. As age increases, the discrimination 
becomes more active and more clearly defined, and finally the 
implant is eliminated. 
The distinctness of this difference in tolerance between upper 
and lower age groups within the female sex suggests that the 
activity of the ovary is intimately concerned with the assump- 
tion of the full development and activity of the individuality 
differential. It may therefore follow that a form of sex limita- 
tion is involved in the activity of certain of the hereditary factors 
under consideration. The transmission of these factors through 
the male as in the case of other sex limited characters is certain.’ 
The (B.C.) series tabulated according to sex in table 7 gives 
distinct evidence of a new type of situation. The same prin- 
ciples of individuality differentials hold, but are somewhat 
modified by the presence within the race of the genetic factors 
possessed by Japanese waltzing mice. When those factors neces- 
sary to support continued growth of an implant of the J. W. B. 
tumor are present, a susceptible animal results. The ratio of 
these to non-susceptible animals does not need to be treated in 
2 Care should be taken not to confuse this with sex-linkage, of which no sign 
exists. é 
