No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 467 
nodules of its meshes) stains a lilac-blue color. And since 
it is wholly improbable that it should be derived from the 
chromatin we must conclude that it takes its origin from 
the nucleolus. In other words, a substance emanates from the> 
nucleolus and dissolves in the nuclear sap, and this process 
must be regarded as the commencement of the dissolution of 
the nucleolus. In support of this conclusion is the fact that 
in many germinal vesicles the nuclear sap stains most intensely 
in the neighborhood of the nucleolus (Fig. 309). Further, the 
minute red-staining globules which later occur in the nuclear 
sap must also be nucleolar in point of formation, i.e., be either 
a substance given off in globular form from the nucleolus, or 
be accumulations (perhaps chemically changed by the action of 
the nuclear sap) of that nucleolar substance which has already 
diffused through the nucleus. Of importance in this connec¬ 
tion is the fact that these globules are often found in contact 
with the nucleolus (Figs. 306 and 316). In all preceding stages 
the nucleolus is regularly oval or spherical in outline, but in 
the largest germinal vesicles not only may the size of its con¬ 
tained vacuole be increased to such an extent that the original 
ground substance forms only a thin shell around it (Figs. 308, 
312, 314), but also its outline becomes frequently irregular 
(Fig. 313); and in one case I found it broken at one pole, so 
that its large vacuole communicated with the cavity of the 
nucleus (Fig. 315). A morphological change in the shape of 
the nucleolus which seems to take place with great regularity 
consists in the indentation of the nucleolar wall at that point 
where it is thinnest (Figs. 308, 314, 316). It would seem that 
the pressure from without, i.e., the pressure of the nuclear sap, 
being greater than the pressure of the fluid within the vacuole, 
would cause the nucleolar wall to be pressed in at that point 
where it is thinnest. The fact remains that the nucleolus 
persists in the nucleus until a very short time before the pro¬ 
duction of the pole spindle, and when the latter is formed no 
trace of it can longer be found in any part of the nucleus or 
cell. And since there is no reason for supposing that it is 
extruded from the cell we must assume that it dissolves 
within it. The red-stained substance and small globules 
