CELLS FROM BRANCHIOBDELLA, ETC. 137 



protoplasm and those of the nucleus. The protoplasmic 

 framework appears almost entirely unstained, and hence 

 very pale. The figure gives a picture of its arrange- 

 ment which is as true as possible to nature, not a diagram. 

 The meshes were drawn in exact correspondence to nature, 

 as far as they could be traced. The gaps in the framework 

 depend, therefore, partly on the meshwork not being distinct 

 enough in places to permit of an accurate drawing, and partly 

 on the existence of real gaps, which depend in their turn on 

 the presence of large' vacuoles, or here and there on local 

 ruptures which are so easily brought about in the preparation 

 of such thin sections. 



The meshed' structure of the protoplasm was further 

 observed by me in the cells of the intestinal epithelium 

 of Branchidbdella, only that here the meshes are directed 

 longitudinally, and hence the protoplasm shows longitudinal 

 striations. The inner ends of the cells possess a cuticular 

 border, which stains very intensely, and is frequently 

 distinctly striated. Finally, these ends carry numerous 

 threads resembling cilia, which seem to bore through the 

 cuticular border. The protoplasmic framework is in like 

 manner stuffed quite full of intensely stained granules. 



The epidermic cells of the skin also show a beautiful 

 reticulate meshwork, with large quantities of strongly 

 stained granules in the nodal points (Plate VII. Fig. 3, a). 



In favourable sections of the cuticle, which did not stain 

 in the slightest, it may be seen to consist of several layers, 

 the height of which is about equal to the diameter of an 

 alveolus of the framework of the cells of the epidermis. 

 Each of the layers is distinctly vertically striated (Plate VII. 

 Fig. 3, a), and therefore presents more or less the appearance 

 of an alveolar layer. In other parts of the cuticle, on the 

 contrary, the alternating layers differed somewhat, one being 

 light, the other dark, and thus the total appearance being 

 somewhat as represented in Fig. 3, 6. In surface view the 

 cuticle appears, as shown in Fig. 3, c, diagonally striated with 

 -distinct dark nodal points. From these observations it 

 seems to me obvious that a meshed, or rather alveolar, 

 structure appertains to the cuticle also, and that therefore 



