The finer Structure of the Nerve Cells of Invertebrates. 33 



cells of Limax, may not be fundamentally the same as that which is 

 known to produce a similar difference in the retinal cells of Verte- 

 brates ? 



The following results, which have been obtained by me, have led 

 me to the conclusion, that the cause which produces this 

 difference is fundamentally the same in both cases; — 

 namely, that the intense staining capacity of the cell 

 body, and lack of the same for the axis-cylinder pro- 

 cess in Limax, are due respectively to the presence and 

 absence therein of chromophilous granules. Further, 

 that these granules correspond in their form, size and 

 mode of distribution in the cell, with those already 

 described in connection with sections on the preceding 

 pages (methylen blue-eosin preparations). 



My own investigations, on the progressive staining of ganglion 

 cells, were made upon those of Limax, which was the only form 

 obtainable at the time. 



Fig. 8 represents a ganglion cell of Limax, the outline of which 

 was drawn with the aid of a camera. The details, however, were 

 drawn in by free-hand, but represent with some degree of accuracy 

 the conditions met with. 



The figure represents a stage in which there is a marked dif- 

 ference in the manner in which the cell body and axis-cylinder pro- 

 cess are stained. The axis-cylinder process is lightly 

 stained, and parallel striations can be plainly seen 

 running in the direction of its long axis. 



The body of the cell, however, is darkly stained, and by careful 

 focussing, is seen to contain a large number of small granules 

 which are stained a deep blue. It is also to be observed that 

 the cell body, between the granules, stains much lighter than the latter. 



These granules appear to be arranged in rows which run more 

 or less concentrically in the cell, and usually in undulating lines. They 

 appear to overlap each other in places, and thus produce an ex- 

 tremely complicated picture which was impossible to reproduce with 

 a camera-lucida. 



On account of the joint appearance of both fibrils (striations in 

 axis-cylinder), and granules in the cell. Fig. 8 might be said to com- 

 bine both Dogiel's "First" and "Second Periods". A stage beyond 

 this, however, is one that directly corresponds to his "Third Period", 

 in which the contrast between the coloration of the axis-cylinder 



Zool. Jahrb. XI. Abth. f. Morph. g 



