218 Papers from the Department of Marine Biology. 



cone itself, it is clearer and more decidedly fibrillar in texture than 

 the dendrites, being free from the chromophyllic substance which is 

 found in these processes. In some cases the neuraxon is shown 

 unbroken in the teased preparations for a distance of six or seven 

 times the diameter of the cell. Plate 3 shows nine of these cells, in 

 which the condition just stated can be easily seen. 



The structure of the cytoplasm is of interest in regard to some 

 possibilities as to a polarity and orientation of the elements of the cells. 

 As observed in sections stained in most of the usual ways and in macera- 

 tions of several kinds, and particularly by careful study of the living 

 cells under the best and highest-powered lenses, it consists of the 

 following substances: 



First, a delicate protoplasm which pervades all parts of the cyto- 

 plasm as a reticulum. It is not stainable with the chromatic dyes 

 and is only seen in certain torn parts of stained sections when deeply 

 stained with eosin or acid-fuchsin. It is not easily distinguishable 

 from the fibrillar substance which appears to make up the bulk of 

 the cell-body. This fibrillar material is seen in both stained and 

 unstained specimens as a "fibrillar mass" which passes into or out of 

 the cell through both dendrites and axis-cylinder process and which 

 forms at various points more marked paths through the cell-body 

 than at others. It does not stain with the ordinary dyes and has been 

 demonstrated by Apathy, Mann, Hatai, and others, to be, or to contain, 

 a series of fine, sharp, and continuous fibrils running in bundles and 

 courses that appear to be the possible pathways of the nerve impulse. 

 As this material seems to determine no polarity of the cell that bears 

 upon our main point, I shall not consider it further. 



Another material is the well-known Nissl substance or chromophyllic 

 substance, which appears in the form of fine granules. Its most promi- 

 nent pecularities are that it stains with the chromatin dyes in a fairly 

 strong way, that it has about the same index of refraction as the fibrillar 

 mass in the living cell, and that, in this electric cell at least, its compo- 

 nent granules are not sharply defined bodies, but seem to be soft or 

 jelly-like in varying degrees, according to the fixation and staining 

 processes that the cell is subjected to. It is scarcely visible in life 

 (plate 2, fig. 3). 



The arrangement of the granules in masses of various sizes, known 

 as the Nissl bodies or tigroid bodies, is a natural one. They are packed 

 by the various crossing and turning bundles of fibrillar substance into 

 the spaces that he between their various courses. Thus, they are often 

 spindle-shaped or three-cornered. Also, where very many bundles of 

 fibrils must be crowded into a compact parallel mass, these bodies 

 are excluded as a mechanical necessity, as is seen particularly at the 

 point in the cell where the axis-cylinder process is about to leave the 

 cell, the implantation cone. The chromophyllic substance is also 



