GROWTH OF A TRANSPLANTABLE TUMOR IN MICE 323 
this paper. Their presence, however, would mean a certain 
number of mice which showed growths in all of the observations 
taken, in addition to those animals which were merely showing 
temporary growth. The curve in figure 1 coming to a constant 
level at about 13 per cent shows the presence of such susceptible 
animals. 
The interesting fact shown by table 2 is that the mice which 
were twenty or more days old at inoculation show a much higher 
percentage of growth than do albinos of the same age. ‘The 
number of eighteen- and of sixteen-day mice are small, but if 
they are lumped together in order to get more reliable numbers 
it is found that their growth percentage is also higher than the 
corresponding classes of common mice; being 23.5 as against 11.2. 
The result is seen in table 5, where the lower age group of the 
(B.C.) generation has a growth percentage of 13.77 +1.05—a re- 
sult practically the same as the 12.87+0.6 per cent of the simi- 
lar age group of common mice. The higher age group of the 
(B.C.) generation, however, has a growth percentage of 21.58 + 
1.28 and differs from the lower group of the same generation by 
4.6 times the probable error and from the higher age group of 
the common (N) series by more than eight times the probable 
error, 
It is obvious that there are here some new conditionsnot found 
in the (N) series. The factors of the Japanese mouse complex 
carried by certain animals of the (B.C.) generation furnish the 
explanation. Producing by their united action permanent pro- 
gressive growth of the tumor, certain of the factors of the J.W. 
complex, even when separated, must in some cases exert a favor- 
able and active influence upon the temporary growth of the tumor. 
This influence will not be felt until they become active agents 
in the individuality complex of the animal possessing them. 
Just as the female mice of the higher age group of the non-sus- 
_ ceptible (N) series common mice developed with the oncoming of 
sexual maturity, their individuality differential of unfavorable 
characters resulting in elimination of the implant, so the females 
of the higher age group of the (B.C.) generation may be ex- 
pected at a similar point to develop in an active condition certain 
