No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 473 



case (Fig. 41) I found three nucleoli of approximately equal 

 dimensions and homogeneous ; usually they vary somewhat in 

 size and contain vacuoles. The shape of the nucleoli is either 

 spherical or oval, or it may be irregular; certain ones stain 

 scarcely at all, and appear granular : these might represent 

 cases of degeneration. 



Smallest ganglion cells (Fig. 36). — Here a single nucleolus 

 is the rule, though two may occasionally be found. They are 

 spherical or oval, and vary considerably in size. Vacuoles do 

 not seem to occur in them, though they might well escape 

 observation from the small dimensions of the nucleoli, which 

 often renders it difficult to distinguish the nucleoli from the 

 larger chromatin granules. 



In all these ganglion cells the chromatin appears in the form 

 of small granules, but on a preparation fixed with Hermann's 

 fluid and stained with Lyons blue (Fig. 45) it appeared as a 

 network ; in this preparation the granules seemed to be united 

 by fine fibers, which stained less intensely than the granules. 

 But even here the connecting threads might consist rather 

 of linin than of chromatin, since the solution of Lyons blue 

 employed by me stained all the nuclear substances except the 

 nuclear sap (paralinin). Such fibers often appear to radiate 

 outwards from the surface of the nucleoli, as if the latter were 

 suspended by them. The nucleoli always stain differently from 

 the chromatin. 



There is, as a rule, a relatively small amount of nucleolar sub- 

 stance in the cells of the second and third types in comparison 

 with most of the other nuclei which I have examined ; but the 

 nuclei of those of the first type, on the contrary, usually contain 

 a relatively large amount of this substance, for not only may 

 one or two of the nucleoli in a nucleus be quite large, but also 

 a considerable number of nucleoli are frequently present. 



13. Ganglion Cells of Montagua pilata (Verr.). 

 (Plate 22, Figs. 90-97.) 



(The same types of cells may be roughly distinguished as in 

 Do to.) 



