The finer Structure of the Nerve Cells of Invertebrates. 41 



In some cells the fibrils, on entering the cell body, run for some 

 distance in the cell free from granules, and form a half-moon- 

 shaped area (Polstelle, Eintrittsstelle, Ursprungshügel), 

 similar to that described by Nissl, v. Lenhossek, Reinke, Flemming, 

 Held and others for the nerve cells of Vertebrates. 



This half-moon-shaped area is most clearly shown in sub- 

 limate preparations which have been stained by the double stains 

 (methylen blue-eosin, etc.). It is also clearly shown in all other pre- 

 parations (see Figs. 3 and 4; also Fig. 15). Compare Figs. 3 and 4 

 with those of Flemming (10, tab. 19, figs. 5 and 12), and Held (16, 

 fig. 2, tab. 13). 



Previous investigators have figured in their drawings of Inverte- 

 brates nerve cells, what corresponds to this non-granular half-moon- 

 shaped area (Binet, Pflücke), but have made no reference, so far 

 as I am aware, to its exact correspondence with similar areas in the 

 nerve cells of Vertebrates. 



In thin sublimate sections, which have been stained by the iron- 

 alum-haematoxylin method, the fibrils are also plainly seen in the 

 axis-cylinder processes, and, so far as their general arrangement 

 therein is concerned, I have nothing to add to Rohde's recent in- 

 vestigation upon this subject, in which he figures them as exceedingly 

 fine fibrils, running parallel to the long axis of the process (see 37, 

 tab. 24, fig. 3 b). Compare with my Fig. 14. 



The appearance presented by the fibrils in the axis-cylinder pro- 

 cesses of nerve cells {Helix, Arion), which have been stained by the 

 double stains (methylen blue-eosin and safranin-light green), is not as 

 clear as in those sections which have been stained by the iron-alum- 

 haematoxylin. 



Double-stained preparations, when properly differentiated, show 

 faint parallel striations in the axis-cylinder processes. Such striations 

 agree in all respects with what have already been described as fibrils 

 in other preparations, and cannot [possibly represent anything else 

 (Figs. 2, 3, 4 and 6). 



In properly differentiated sections, these striations stain a 

 deeper red or deeper green, as the case may be, than 

 the ground-substance of the process, and much lighter 

 than the coarse neuroglia fibrils which envelop the 

 process. The striations in the axis-cylinder process, however, stain 

 very similarly, and agree, in the size of their calibre, with certain fine 

 fibrils in the neuroglia. 



