Theories of Chemical Development 149 
peculiarity in a definite part of the organism, if it does not 
seem quite impossible, certainly seems difficult to con- 
ceive. It is true that these theories of the Spencer type 
can always bring up the objection that to a visible varia- 
tion of a certain group of cells there might possibly cor- 
respond similar variations in all the other cells of the 
organism, but always so small that they are not appre- 
ciable. But such an explanation of the especially inherit- 
able variations would be formal rather than actual. 
This applies equally well, it may here be said paren- 
thetically, to evolutionary theories without preformed 
germs, such for example as the theories which are called 
those of the chemical development of the egg. They start 
out usually with a heterogeneous germ substance, con- 
stituted by multiple and diverse chemical substances, from 
chemical interactions of which new chemical compounds 
are formed later, which give place in their turn,—in each 
cell as in a separate crucible independent of the others,— 
to new chemical reactions and consequently to new com- 
pounds different in the different cells, and so on up to the 
end of development. But one cannot conceive how each 
one of these components of the germ substance, which 
commences to exercise its chemical action upon the other 
constituents from the very first moment of development, 
even though it be the only point in which one germ differs 
from another, can bring about an alteration of the or- 
ganism limited to a single point rather than an alteration 
extended over the entire organism. 
The argument brought up by the partisans of pre- 
formistic germs, both epigenesists and preformationists 
properly so called, is then really weighty enough to force 
us to hold as inadmissible every biogenetic hypothesis 
which starts out from or is based upon a homogeneous 
