MONTGOMERY. 
[Vol. XV. 
482 
may be dense and stain deeply; other portions are less dense in 
structure, with a corresponding less intensity of stain; and still 
other portions of the cell substance appear structureless and 
do not stain at all. The cytoplasm in at least a portion of the 
peripheral area of the cell is always dense and deeply staining ; 
rarely is the cytoplasm in the whole cell of this dense structure. 
With low powers of magnification (e.g., Zeiss Obj. C, oc. 2 or 4) 
there may appear to be either several cavities in the cytoplasm 
or a single large one at one side of the nucleus. These differ¬ 
entiations of the cytoplasm (which fixation in corrosive subli¬ 
mate or in Hermann’s fluid bring out always in the same manner) 
probably denote certain metabolic states of the cytoplasm, but 
it would be difficult to determine from the structure alone to 
what physiological processes these states might correspond. 
There is no definite secretion produced by the cytoplasm, i.e ., 
no secretion with a definite form. As has been noted, a wholly 
or nearly wholly clear space often occurs in the cytoplasm at 
one side of the nucleus ; such a space usually lies at that 
margin of the nucleus situated closest to the center of the cell, 
and the nucleus may often surround it to some extent. Where 
the nucleus comes into contact with this space its membrane is 
thinnest and its outline irregular, and quite frequently this 
margin of the nucleus is produced into long, irregular, amoe¬ 
boid processes, which extend into the space in question and 
pass around it. These appearances would show that the 
nucleus stands in a certain functional relation to the metabolic 
changes of the cytoplasm, not improbably that it assimilates 
certain substances produced in the latter. 
To return to the nucleoli, I cannot find any genetic connec¬ 
tion between these structures and the cytoplasm. They are 
usually grouped near the center of the nucleus, and though 
often quite peripheral in position, never come into contact 
with the nuclear membrane, nor are they found in the amoeboid 
processes of the nucleus. It will be necessary to study very 
young individuals of this mollusc in order to determine the 
mode of nucleolar development. 
The cell (Fig. 339) is developed by a delicate membrane, 
which seems to be interrupted at no point on the surface of the 
