PROTOZOAN NUCLEI. 383 



In addition to the above structure the cells of Tetramitus zox\- 

 tain a number of comparatively large-sized granules which stain 

 intensely with saffranin in the Flemming stain and black with 

 the iron-haematoxylin. In division they are separated into two 

 equal groups in the daughter-cells (Fig. 5). From the relation 

 to stains and the general appearance during rest and division 

 I have no hesitation whatever in comparing them with the 

 granules of chromatin described by Biitschli in the case of Chro- 

 niatiurn and Bacterium tcriiio. The most frequent position of the 

 granules is at the extremity of the cell opposite the flagella, 

 where they form an aggregate of greater or less density, but in 

 which the individual granules can be distinctly made out (Figs. 

 2, 4). There is reason to suppose that this close aggregation 

 indicates the approach of division, for the culture was extremely 

 active and the monads were increasing rapidly. Many indi- 

 viduals were found, however, in which the chromatin granules 

 were distributed over all parts of the cell (Fig. i). Aggregates 

 were also found in the flagella-end of the cell (Fig. 3), although 

 such cases were comparatively rare. In this connection it is a 

 significant fact that division of the body begins at that end of the 

 animal which holds the chromatin, in this case at the posterior 

 end, although the majority of flagellates begin to divide at the 

 flagellate end (Fig. 5). 



This type of nucleus must be very primitive. It has no 

 membrane and no linin unless the meshes of cytoplasm around 

 the chromatin granules be called linin. Is there a nucleolus ? 

 Were it intra-nuclear the cytoplasmic body described above 

 might be called a nucleolus on account of its staining reactions, 

 but it is not intra-nuclear, and furthermore it appears to have a 

 special function in the activity of the cell. Wherever the aggre- 

 gate of chromatin granules may be found the cytoplasmic body 

 is invariably in the near vicinity. It appears to divide before the 

 group of chromatin is halved, and in the daughter-cells of a 

 just-divided form the chromatin granules appear to surround the 

 cytoplasmic body (Fig. 5.) It is certainly conceivable and in 

 view of the phenomena in other allied Protozoa, almost probable 

 that this cytoplasmic body exerts some influence upon the chro- 

 matin granules to attract them about itself at certain stages. 



