21 8 WM. A. KEENER AND J. G. EDWARDS. 



nucleus lies posterior to the middle of the body closely associated 

 with the fundus of the pharynx (Figs. 2 and 3). We have been 

 able to find many of these nuclei in what we take to be the resting 

 condition (Fig. 3). In this condition there is a well-defined 

 nuclear limit indicating the presence of a nuclear membrane. 

 Within the nucleus a single spheroidal nucleolus is seen. This 

 nucleolus in life is highly refractive. The chromatin granules of 

 the resting nucleus are very small and uniform in size. They 

 crowd rather closely upon the nucleolus and leave the nucleolus 

 to lie within a relatively small chromatin-free region (Figs. 3 

 and 6). In other specimens we find the nuclear size to be 

 increased (Fig. 2) and in some cases the shape of the nucleus, 

 as well, is greatly modified (Fig. 5). In most of these enlarged 

 nuclei the chromatin granules lie more remote from the latter 

 within a relatively large chromatin-free region. The chromatin 

 granules themselves, in such nuclei, are greatly enlarged, though 

 yet uniform in size. These enlarged nuclei we had taken to be 

 prophases in mitosis before the appearance of Belar's paper ('16) 

 and now we can say that we are able to corroborate in a general 

 way his earlier details for the mitosis of C. paramcecium. 



Except for these strikingly nuclear-like variations, the char- 

 acter, of what has been termed a "division center," remains 

 constant and we look upon it as the proper nucleus of the cell. 



On the other hand, the variability of the extra-nuclear chro- 

 matic granules is conspicuous in contrast with the slight varia- 

 bility of the nucleus. These chromatic granules vary in number, 

 size and distribution. We have not found an individual in 

 which no granules are present. These chromatic bodies are 

 smallest when fewest and they then lie within the posteiior half 

 of the cell (Figs. I and 5). The granules tend to increase in 

 size as they become more numerous (Figs. 2, 3 and 6). They are 

 most widely distributed throughout the cell when they are largest 

 (Figs. 4 and 6). The granules of a given cell, when they are in 

 this last condition, are no longer uniform in size (Figs. 4 and 6). 



Associated with this variability of the chromatic bodies we 

 have a variability of the paramylum contents of the cytoplasm. 

 The granules are fewest and smallest when the paramylum 

 bodies are relatively most numerous and when the latter lie 



