Theoretically Conceivable Kinds of Epigenesis 107 
sequence of the reciprocal action of the different parts 
of the organism upon one another. 
We will call the first of these processes epigenesis 
with preformistic germs, the other, epigenesis without 
preformistic germs, or epigenesis proper. 
Further, each of these two processes can, theoretically, 
be divided again into the two following categories. 
One can conceive of the reciprocal action of the dif- 
ferent parts of the organism upon one another, as such 
that no part whatever should ever be considered different 
in any way, in so far as its formative action on the other 
parts is concerned, from these other parts, but rather all 
are to be regarded as equally necessary and of equal 
value in this respect. Or, on the other hand one can 
suppose that among all the parts there is one whose action 
upon the other parts differs through some peculiarity 
from the corresponding action of all other parts, so that 
it acquires in comparison with the latter much greater 
importance. 
We shall designate the first process with the name 
“simple epigenesis,” or briefly “epigenesis,” which would 
be equally possible either with or without preformistic 
germs, and we shall call the second in which the form- 
ative action would on the contrary become specially local- 
ized in a definite zone of the organism, by the name of 
“localized or centralized epigenesis,”’ or briefly ‘“centro- 
epigenesis.”” Practically it would be conceivable only 
without preformistic germs. 
Finally, in all the different theories without pre- 
formistic germs, one could conceive of the germinal sub- 
stance as formed of a single homogeneous substance (or 
a homogeneous mixture of different chemical substances), 
or of a material which though not consisting of pre- 
