GERM CELLS OF COELENTERATES 393 
In the stage represented in figure 8 (the egg being a quarter of the 
final size) we have the first indication of these yolk bodies, present 
in greater numbers near the periphery of the egg; when these bod- 
ies become more abundant (figs. 9 to 13) they are present near the 
nucleus as well. Figures 9 and 10 show lines in the cytoplasm 
radiating from the nucleus, which is evidence of currents which 
are proceeding outward from the nucleus, I conceive, therefore, 
that the yolk is built up in the cytoplasm out of material which 
has come from the nucleus, or from the material inthe cytoplasm 
through the aid of material which has come from the nucleus. 
The simplest explanation of this appears to me to be that per- 
haps an enzyme from the nucleus gets into the cytoplasm and 
there elaborates and synthesizes the food brought into the egg. 
The presence of radiating lines—that is, of currents going out 
from the nucleus—is present for a considerable time; indeed 
up to the time when the polar bodies are about to be formed. 
This activity contines, then, throughout the entire history of 
the egg cell, and when it ceases the egg is loaded down with 
yolk granules which are so closely packed as to leave little space 
between them. The granules of the cytoplasm, at first the only 
material present, are now arranged around these yolk bodies and 
between them in a sort of an alveolar arrangement, but apparently 
not much greater in amount than in the young eggs. The differ- 
ence in the appearance of the yolk bodies shown in figures 9, 10, 
and so forth, is apparently without significance, being due to the 
variation in the tenacity with which the bodies hold the stain. 
b. The nucleolus. It is in the peculiarity of the nucleolar 
structure and history that one of the most interesting phases of 
the development of the egg of Campanularia flexuosa lies. And 
let it be remembered that many of the conditions and appearances 
referred to and figured have been seen in the living egg. The liv- 
ing egg of Obelia has also shown similar things so that there is 
no question of the effect of killing agents and so forth, for these 
appearances are faithfully shown in the sections; that is, the nu- 
clear constituents have been normally preserved in the killed eggs, 
even to the delicate features. 
In figures 2 to 4 the youngest egg cells show a single spherical 
nucleolus which stains deeply with iron-hematoxylin, though, with 
