GERM CELLS OF COELENTERATES 403 
soon disappear and the nucleus contains only a very fine meshed 
and slightly staining reticulum (figs. 5, 6). Since the reticulum 
is present only after the loops have disappeared it is evidently 
formed from the loops, though the nucleolus secures some of the ma- 
terial. After the egg reaches its place in the gonophore a rapid and 
marked growth takes place (fig. 1). It is during this period that 
the peculiar nucleolar changes occur which lead to yolk formation. 
Let it again be noted that the dark bodies within and just with- 
out the nuclear membrane in figure 7 to 9 are bodies which have 
left the nucleolus and are passing through the nuclear wall into 
the cytoplasm. These bodies are chromatic in character, since 
the nucleolus has been formed from the dissolving chromatin 
loops of the earlier spireme, and therefore they should present 
essentially the same staining reactions as the rest of the chromatin, 
and such we find to be the case. The nucleolus, therefore, 
appears to be a synthetic or transforming center of the nucleus 
where the chromatin is to be changed somewhat for the function 
it is to perform in the cytoplasm. The fact that these bodies do 
not belong in the reticulum, as an integral part of it, is shown 
by figures 7 to 9; they do not lie in the reticulum itself and the 
latter shows plainly as a delicate and finely granular affair. 
In the late growth period of the egg (figs. 11 to 17) the nucleolus 
breaks into parts of a greater or less size and, as these are sur- 
rounded by vacuoles, it is evident that they are not a part of the nu- 
clearreticulum. And while it may be that the dissolving nucleolus 
adds some material to the reticulum, this does alter the general 
appearance or behavior to stains which the reticulum has shown 
during the earlier part of its growth. Figures 11 and 12, for 
example, show the same sort of a reticulum as is shown in figures 
6 to 8, though a considerable portion of the nucleolus has dis- 
appeared. The point made here is simply this; the chromatin in 
the nucleus is of two sorts or if not actually different in composi- 
tion, at least it serves two different functions in the cycle of the 
cell. A certain portion of the chromatin (that which has gone, or 
goes, into the nucleolus), after some probable transformation 
within the nucleolus, passes out of the nucleolus into the cyto- 
plasm, there to serve a particular purpose, and this portion does 
JOURNAL OF MORPHOLOGY, VOL. 24, NO. 3 
