286 PROTOPLASM 



does not contain many details of structure which the photo- 

 graph represents very well. In this regard I may refer, by way 

 of example, to the nucleus alone, the contents of which are 

 described and depicted as granular, while the photograph 

 shows distinctly that the granules are lodged in a honey- 

 combed framework. I regard, therefore, as has been said, 

 Eohde's photographs, as well as those of a ganglion cell from 

 an earthworm which accompany the present work, as good 

 evidence of the alveolar structure. The photograph in 

 question teaches us still more, however. Rohde describes 

 and figures the fibrillse of the ganglion cells as being of 

 very different thicknesses, and asserts that in certain zones of 

 the protoplasm very strong fibrils make their appearance, 

 while in other regions there are only very fine ones. In a 

 former section I have already pointed out that the stronger 

 fibrils, or " runners " (Reiser), so often described, are quite 

 certainly only the result of densely deposited granules. Now 

 Rohde's photograph, already mentioned, also seems to me to 

 bring forward the strongest proof in favour of this explanation, 

 for it can be plainly made out in it in many places that 

 the apparent stronger fibrillae arise by a more or less dense 

 crowding together of such granules, and it can further be 

 seen with the same distinctness that the differences between 

 the five zones of protoplasm which Rohde distinguishes 

 depend in the main, at any rate, upon differences of the 

 degree to which they contain granules lodged in them, to- 

 gether with, however, special modifications of the framework 

 here and there. On the other hand, the width of the meshes 

 does not seem to me to be subject to any very considerable 

 amount of variation in the different zones. The fact that 

 the zones, with very numerous granules, appear in general 

 more finely structured, may rather depend essentially on all 

 the nodal points being sharply marked out by the granules 

 lodged in them, while in the zones poor in granules many 

 nodal points are so pale that they are only slightly promi- 

 nent, or even partly left out in the photograph. 



Now since, as has been said, I find in this photograph of 

 Rohde's an involuntary support for my interpretation of the 

 structure of ganglion cells and of protoplasm generally, I 



