Embryology. i 
absolute. As in the case of sexual propagation, so 
in that of karyokinesis, processes which are common 
to all the Metazoa are not wholly without their fore- 
shadowings in the Protozoa. And seeing how greatly 
exalted is the office of egg-cells—and even of tissue- 
cells—as compared with that of their supposed ancestry 
in protozoal cells, it seems to me scarcely to be 
wondered at if their specializations of function should 
be associated with corresponding peculiarities of 
structure—a general fact which would in no way 
militate against the doctrine of evolution. Could 
we know the whole truth, we should probably find 
that in order to endow the most primitive of egg-cells 
with its powers of marshalling its products into a 
living army of cell-battalions, such an egg-cell must 
have been passed through a course of developmental 
specialization of so elaborate a kind, that even the 
complex processes of karyokinesis are but a very 
inadequate expression thereof. 
Probably I have now said enough to show that, 
remarkable and altogether exceptional as the pro- 
perties of germ-cells of the multicellular organisms 
unquestionably show themselves to be, yet when these 
properties are traced back to their simplest beginnings 
in the unicellular organisms, they may fairly be re- 
garded as fundamentally identical with the properties 
of living cells in general. Thus viewed, no line of real 
demarcation can be drawn between growth and repro- 
duction, even of the sexual kind. The one process is, 
so tospeak physiologically continuous with the other ; 
and hence, so far as the pre-embryonic stage of life- 
history is concerned, the facts cannot fairly be regarded 
as out of keeping with the theory of evolution. 
