THE BEARERS OF THE HERITAGE 295 
in which a single large, primordial germ-cell (p. g.c.) has already been 
set apart at one end of the developing embryo. The nuclei of the rest 
of the embryo still lie in a continuous protoplasmic mass which has 
not yet divided up into separate cells. The densely stained nuclei at 
the opposite end of the section are the remnants of nurse-cells which 
originally nourished the egg. Fig. 45, B, is a longitudinal section 
Fic. 45.—A, germ-cell (.g.c.) set apart in the eight-celled stage of cleavage 
in Miastor americana. (After Hegner.) The walls of the remaining seven somatic 
cells have not yet formed, though the resting or the dividing (M ) nuclei may be 
seen; c R, chromatin fragments cast off from the somatic cells; B, section length- 
wise of a later embryo of Miastor; the primordial egg-cells (06g3;) are conspicuous. 
(From Guyer, after Hegner.) 
through a later stage in the development of Miastor; the primitive 
germ-cells (odg) are plainly visible. Still other striking examples 
might be cited. Even in vertebrates the germ-cells may often be 
detected at a.very early period. 
Significance of the early setting apart of the parciccate tes is 
of great importance for the reader to grasp the significance of this 
early setting apart of the germ-cells because so much in our future 
hinges on this fact. The truth of the statement made in a previous 
chapter that the body of an individual and the reproductive substance 
