48 CHARLES F. W. MC CLURE, 



axis-cylinder pole of the cell. Compare Flemming's fig. 1 and 2 with 

 my Fig. 11, in which a similar disposition of the fibrils is met with 

 at the axis-cylinder pole of the cell. 



In that type of cell, which is represented by my Fig. 20, the 

 arrangement of fibrils approaches nearest to that represented by Flem- 

 MiNG, as characteristic of the spinal ganglion and central nerve cells. 

 In this cell, however, the fibrils are not as winding as those figured 

 by Flemming. 



DoGiEL (8, fig. 6) has recently figured a double concentric system 

 of fibrils as characteristic of the spinal ganglion cells of Mammals. 

 He finds that the larger cells contain a large number of small 

 chromophilous granules (Körnchen) which are arranged 

 in rows between the fibrils in the cell body. An examin- 

 ation of his fig. 6 shows that this arrangement of granules 

 is essentially the same as that figured by me for the 

 nerve cells of Gastropods. 



Since the appearance of Dogiel's paper, I have considered it 

 quite probable that two concentric systems of fibrils may be present 

 in the nerve cells of Gastropods, but I have been unable thus far to 

 definitely substantiate this view, either by a study of sections (longi- 

 tudinal and transverse), or by the methylen blue method made use of 

 by Dogiel or that used by myself. 



The only evidence thus far obtained by me in favor of this view 

 is the circumstance that in many sections of cells, one finds fibrils 

 and granular rows which run almost at right angles to each other. 

 Theoretically, it would seem possible to determine this question by a 

 study of sections out in two planes. This, however, as far as my 

 experience is concerned, has not proved practicable and, at the present 

 writing, I feel compelled to leave this question in abeyance. 



I will say in concluding this part, that the ground type arrange- 

 ment of the fibrils, in the nerve cells of Gastropods, appears in the 

 majority of cases to be a concentric one. That the presence of fibrils 

 in the same section, which do not conform to this arrangement, may 

 possibly be explained on the ground, that they belong to a second 

 concentric system; or, if only one concentric system be present, they 

 may represent fibrils which have been bent out of their concentric course 

 in correlation with functional changes in the cell, or in connection 

 with the action of fixing and hardening reagents. 



