230 
an efFect of non-genetic factors is possible because of the cxperi- 
ments of Tower. But in such a case it is very improbable that 
the falling-out of a genetic factor should produce an effect on 
the taillength rather than on the colour or on the form of the 
animaPs humerus or anything eise. 
It is very far from probable that the mice, whose taillength 
is modified by Przibram by subjecting them before or after birth 
to a different temperature, will produce offspring with longer 
tails than normal mice, on condition that these young will not 
themselves be either before or after birth subjected to the changed 
non-genetic factors for taillength. Hitherto the alleged cases of 
the inheritance of modifications are all based on a play of words, 
reckoning the new generation to begin at birth, instead of at 
the formation of the Zygote, so that the effects of non-genetic 
factors on an unborn individual can be attributed to the modifi- 
cations of its mother. A beautifull example of this is seen in 
the recent experiments of Kammerer. He found that a certain 
lizard, in a high temperature changed the white colour of its 
abdomen into red. He found that the young born from such a 
lizard had the colour of their mother. When this was red through 
high temperature, the young born were red, when the mother 
had lost its red colour after being brought back into a lower 
temperature, the young born were normal. He now found, that 
when he brought back the mother to a low temperature before 
the birth of the young, these young, when born sufficiently early 
after the change of temperature, were still red. He concludes 
from these facts that the effect of the temperature is transmitted. 
In a certain sense it is, for, as the young are inclosed in the 
body of the mother, they can only receive the additional heat 
through the intermediary of the tissues of the heated mother. 
Of course it is wordplay to call such a process by the name of 
heredity. One could as well say, that, as the offspring of heated 
lizards are born hot in a high temperature, this temperature was 
inherited. The fact that the young lizards, born after the mother 
has had time to cool off are born cold but still redbellied only 
shows that the red colour resulting from a hot environment 
persists longer than the body-temperature itself. 
As to the development of each individual of a strain coope- 
rate about the same set of non-genetic factors, and as the 
reaction of the development on these factors is always essentially 
