The finer Structure of the Nerve Cells of Invertebrates. 47 



in character than those seen in Fig. 11, and many of them do not 

 maintain a concentric course about the nucleus. 



In addition to the above mentioned types, I have met with cells 

 in which the fibrils and granular rows, instead of being winding in 

 character, run concentrically about the nucleus parallel to each other. 

 This condition was met with chiefly in the smaller cells, and was 

 particularly prominent in that region of the cell body contiguous to 

 the nuclear membrane (Fig. 17, Ganglion cell of Helix, Flemming- 

 iron-alum-haem.). 



A marked parallel arrangement of fibrils and granular rows was 

 also found in certain small bi-nuclear ganglion cells, which will be 

 spoken of more in detail further on (Figs. 18 and, 19 Ganglion cells 

 of Helix, Sub.-iron-alum-haem.). 



Finally, sections were met with in which a marked concentric 

 arrangement was not to be seen, but in which the fibrils and granular 

 rows appeared to be arranged in the cell body without any definite 

 system. 



Fig. 20, which is a ganglion cell from the infra-oesophageal 

 ganglion of Helix (Sub. and Delafield's haem.), represents this type 

 of cell. The section from which this drawing was made was 2 u in 

 thickness. The individual fibrils in the axis-cylinder process were not 

 clearly brought out in this preparation, but the boundary line between 

 the process and cell body was most distinct. An examination of this 

 figure shows that the fibrils in the cell body are exceedingly winding 

 in character, and that their arrangement therein is purely arbitrary. 

 Such sections as this, in which there is no indication of a concentric 

 arrangement, are not commonly met with. 



An examination, of the above mentioned figures, shows that, in 

 certain of these Gastropod nerve cells, an arrangement of fibrils 

 is present, which is strinkingly similar to that described by Flemming 

 (10, 11), for the spinal ganglion cells of Mammals and the central 

 nerve cells of Vertebrates. 



Flemming's winding fibrils, however, diifer as a rule from mine, 

 in that they are more winding in character, and that they are never 

 concentrically arranged about the nucleus. 



In his figs. 5 and 12 of spinal ganglion cells (see 10), the ar- 

 rangement of fibrils in the axis-cylinder process and in the "Pol- 

 stelle", is the same as that represented by me for Gastropod nerve 

 cells. In his central nerve cells (see 11, figs. 1 and 2), the fibrils 

 are represented as running a parallel course in the cell body at the 



