404 GEORGE T. HARGITT 
not take part in the reproductive activity of the cell. The second 
portion of the chromatin plays little part in the described activi- 
ties of the growing egg, but at a certain period is essential for the 
reproductive phase. It is not considered that the chromatin 
intended for differing functions is fundamentally different, for, 
as already noted, both the reticulum and a portion (if not all) 
of the nucleolus has come from the same original source, namely, 
the chromatin skein in the young egg cells. Nor is it conceived 
that the chromatin, thus having one function, does not take any 
part in the other function or receive additions from the other 
portion of the chromatin. ‘There is certainly an interaction be- 
tween the nucleus and the cytoplasm, as well as between the nu- 
cleolus and the rest of the nucleus; the whole cell is a unit and it so 
works. But there appears to be some division of labor, and in 
analyzing conditions, functions, and substances, it is convenient 
to think of them separately. 
To summarize the previous paragraphs: There has been no 
apparent modification in the nuclear reticulum by the dissolving 
nucleolus, nor is the preparation of the nucleus for division depen- 
dent upon a certain stage of nucleolar dissolution, for, as figure 
13 shows, a large number of nucleolar fragments are still present 
and the chromatin of the reticulum is beginning to condense into 
strands at certain places. On the other hand, some nuclei, not 
included in the figures, show the nucleolus practically goneand 
there is only a faint reticulum. But there comes a time, at the 
end of growth, when the chromosomes begin to form. ‘This may 
be by the formation of strands in the nuclear reticulum, as shown 
in figures 13 and 16, or it may be initiated by the condensation of 
the chromatin at the nodes of the reticulum (figs. 14, 17). In 
some cases the whole reticulum appears to become coarser, the 
grains composing it larger and staining more deeply (fig. 15). 
In many nuclei all these methods are active. But figures 13 to 17 
show clearly that at the end of growth the nuclear reticulum, 
hitherto very delicate and lightly staining (figs. 7 to 12), shows the 
beginning of a segregation and a condensation of its substances 
which go to form the chromosomes, and the latter form only from 
the reticulum. This appears to involve the nuclear reticulum 
