482 MONTGOMERY. [Vol. XV. 



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 occui's 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 



