136 PROTOPLASM 



zone of the epithelium, and therefore have not as yet passed 

 through the body of the gland cells, but only through their 

 efferent tubules, which run up between every two contiguous 

 supporting cells, it is possible to make out in addition the follow- 

 ing state of things. Each transverse section of a supporting 

 cell is surrounded by a very beautifully developed radiate layer 

 of alveoli, distinguished by staining strongly in hsematoxylin. 

 The alveolar layers of contiguous cells are in direct contact, 

 so that their pellicles form only a single sharp dark limiting 

 line. Every efferent tubule of the gland cell is therefore 

 surrounded by the alveolar layers of two neighbouring cells, 

 which here separate from one another to a slight extent, in 

 order to form the lumen of the tubule. The protoplasm of 

 the supporting cells shows a beautiful reticulate meshwork 

 in transverse section, sometimes with a slightly radiating 

 arrangement. 



7. Peritoneal Cells on the Gut of Branchiobdella astaci, etc. 



In very fine transverse sections of specimens of this 

 worm preserved in picro-sulphuric acid, I have observed the 

 protoplasmic structure very plainly, especially in the cells 

 mentioned above, but also in numerous other cells of the 

 body. Fig. 2, Plate VII., represents a section through a 

 cell of this kind, which was stained intensely on the slide 

 with gentian violet in aniline water. The thickness of the 

 section may have been at most 1 /JL, but was without doubt 

 still less, since the investigation shows definitely that not 

 more than a single layer of the framework of the meshes 

 appears in the section. The appearance offered by the 

 nucleus represents, therefore, a transverse section through it. 

 As is shown by the figure, the protoplasmic framework 

 stands out with excessive distinctness, and is distinguished 

 by having numerous very intensely stained granules lodged 

 in its nodal points. It can be seen definitely, however, that 

 by no means all the nodal points of the framework contain 

 granules, but that fairly extensive regions of the framework 

 are quite free from them. In colouring and appearance no 

 distinction can be made out between the granules of the 



