Embryology. 125 
in a singularly forcible manner. On this account, 
therefore, and also because the facts will again have 
to be considered in another connexion when we come 
to deal with Weismann’s theory of heredity, I will 
here briefly describe the processes in question. 
We have already seen that the young egg-cell mul- 
tiplies itself by simple binary division, after the 
manner of unicellular organisms in general—thereby 
Fic. 33.—Stages in the formation of the polar bodics in the ovum of a 
star-fish. (After Hertwig.) g.v., germinal vesicle transformed into a 
spindle-shaped system of fibres ; Z.’, the first polar body becoming ex- 
truded; ., ., both polar bodies fully extruded; ffz., female pro- 
nucleus, or residue of the germinal vesicle. 
indicating, as also by its amcebiform movements, its 
fundamental identity with such organisms in kind. 
But, as we have likewise seen, when the ovum ceascs 
to resemble these organisms, by taking on its higher 
degree of functional capacity, it is no longer able to 
multiply itself in this manner. On the contrary, its 
cell-divisions are now of an endogenous character, 
