The finer Structure of the Nerve Cells of Invertebrates, 27 



Although usually of spherical form, nuclei were also found by 

 the writer which were invaginated on the side directed towards the 

 axis- cylinder pole of the cell, thus giving to them the characteristic 

 kidney-shaped appearance ^). 



These kidney-shaped nuclei were mentioned by both H. Schultze 

 and SoLBRiG, but, if I understood them correctly, were regarded by 

 them as artefacts. 



In the light of more recent investigations, the writer has ascribed 

 to these kidney-shaped nuclei a somewhat different interpretation; — 

 namely, that they are probably connected with a present or past 

 division of the cell. 



These views were set forth by the writer in a short preliminary 

 paper (22), and will be considered more in detail further on. 



Before entering upon the topic of the finer anatomy of these 

 nerve cells, there are two questions in connection with their gross 

 anatomy which may prove of some interest. 



First, as regards the existence of a peculiar type of bipolar cell, 

 and second, as to the existence of a nuclear process (Kernfortsatz). 



The bipolar cell referred to, is one in which both processes spring 

 from the same pole of the cell, as figured by H. Schultze (40) 

 tab. 5, fig. 1, and by Vignal (43) tab. 16, fig. 15 a, 



I have frequently isolated cells of this character from the oeso- 

 phageal ganglia of Limax maximus. 



In regard to the presence of a nuclear process (Kernfortsatz), I 

 can find no evidence favoring one. Their presence has, however, been 

 noted in the nerve cells of Invertebrates by G. Wagenek (44), 

 OwsjANNiKOw (29), SoLBRTG (41), H. ScHULTZE (40) and more re- 

 cently by RoHDE (38). Schultze describes the nuclear process, with 

 the exception of the nucleus, as staining much more deeply than the 

 remaining portions of the cell, and states that in api)earance it is 

 coarsely granulated; while the other cell processes are finely fibril- 

 lated. He says on p. 74: "Die oft beträchtliche Länge (fig. 3) dieser 

 mit dem Kern die gleiche lebhafte Karmintinction zeigenden Fortsätze, 



1) In many sections in which the large cells appear to be much 

 crowded together, the spherical form of the nuclei may be considerably 

 modified. When such was the case, the form of the cell was similarly 

 changed. These kidney-shaped nuclei, however, were more frequently 

 found in cells, whose walls had not been compressed by adjacent cells, 

 so that the kidney-shaped nuclei cannot in this case be attributed to 

 such a cause. 



