No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 48 1 



conclude from their structure what their function is ; per- 

 haps they have a function similar to that of lymph glands. 

 Such cells are absent in Montagiia.) 



The form of these is a more or less polyhedral one, caused 

 by the pressure of the surrounding organs (Fig. 339). The 

 nucleus is relatively and absolutely very large and is very vari- 

 able in form, sometimes irregularly oval, sometimes with obtuse 

 or pointed processes, or again concavo-convex, that side being 

 convex which lies near the nuclear membrane (on a transverse 

 section such a nucleus appears sickle shaped). The chromatin 

 is arranged in the form of rather coarse granules (Figs. 339 

 and 342), which after fixation in Hermann's fluid (Fig. 340) 

 appear to be the nodal points of a reticulum. 



The nuclei (Figs. 338-346) are numerous, vary in number 

 from about six to about forty, and are irregular in size. Their 

 shape is usually oval, seldom perfectly spherical, though quite 

 frequently, as the figures show, they may be more or less 

 elongate or even very irregular in form. Vacuoles are fre- 

 quently present in them. The nucleoli stain as do all true 

 nucleoli, but different degrees of staining density may be 

 observed in the nucleoli of the same nucleus (Figs. 338, 342, 

 346). In two cases, one of which is here figured (Fig. 342), a 

 dense ring of chromatin was found around a nucleolus, but such 

 cases, judging from their infrequency, must be regarded as very 

 abnormal, if not attributable to the action of the fixing fluid. 

 Divisions of the more elongate nucleoli certainly take place. 

 Thus I have observed dumbbell-shaped nucleoli in three cases 

 (Figs. 343, 345, 346), and Fig. 340 probably represents a stage 

 just after a division, where two smaller nucleoli have apparently 

 been divided off from a larger one, one end of the latter being 

 drawn out to a point. Thus it might seem that the large num- 

 ber of nucleoli are produced by divisions of a smaller number 

 of larger nucleoli. The variability in the size, form, and 

 number of these nucleoli recalls those of the subcuticular gland 

 cells of Piscicola (cf. infra) ; but in these cells of Doto I have 

 been unable to make out different morphological phases. 



The cytoplasm of these cells is also remarkably differentiated 

 (Fig. 339). In a given cell certain portions of the cytoplasm 



