THE FACTORS OF ORGANIC EVOLUTION. 105 
reasoning from the tissue cell to the egg cell in order 
to see that there is no escape from the conclusion that 
the whole course of developmental phenomena must be 
referred to organization of some sort. Development, 
no less than other vital phenomena, is a function of 
organization.” 
3. A study of the phenomena of development, as 
well as.the principle of causality, make it certain that 
all the characters of the species are pre- 
Inherited charac- determined within the protoplasm of the 
ters predeter- fertilized egg cell. From a frog’s egg 
mined in struc- f : 
rare of eermicell: only a frog will develop, from an echino- 
derm egg only an echinoderm, and the 
course of the development is, under normal circum- 
stances, definitely marked out in each case, even down to 
the minutest details. All the results of experiment, as 
well as observation and induction, only serve to render 
this conclusion the more certain. It should be observed 
that to affirm that characters are predetermined is a 
very different thing from saying they are preformed. 
The one merely asserts that the cause of the transforma- 
tions which lead from one step to another in the devel- 
opment is determined by the initial conditions of the 
fertilized egg cell; the other affirms that those trans- 
formations have already taken place. 
'The absolute determinism of development depends 
primarily upon the constant structure of the egg cell, 
but also to a certain extent upon a definite relation to 
extrinsic factors. Since, however, these extrinsic fac- 
tors may be exactly the same in two cases, and yet the 
result of development be very different (e.g., the egg 
of the starfish and that of the sea urchin), we can only 
conclude that while ontogenetic differences may be 
caused by a disturbance of the extrinsic factors, inherited 
characters are always the result of a definite structure of 
