^à CHARLES F. W. MC CLURE, 



that the above warning should apply with equal force to all of us 

 who are interesting in furthering this line of research. 



My own investigations on this subject may be briefly described 

 as follows: In connection with the following description, Figs. 21 and 

 22 should be consulted. In certain unipolar ganglion cells of Helix 

 which have a transverse diameter ranging between 17 and 22 mm, 

 the nucleus was found in longitudinal sections to have an eccentric 

 position. In addition to this, in such cells the side of the nucleus 

 directed towards the axis-cylinder pole of the cell was often flattened, 

 or more frequently invaginated, so that the nucleus presented 

 a kidney-shaped appearance. The flattened or invaginated 

 side of the nucleus was never found to be directed exactly 

 opposite to the base of the axis-cylinder process, but 

 always to a point on one side of it. 



In the body of the cell , directly opposite the invagination , a 

 disk-shaped structure was found. The position of this disk 

 was found to be variable; in some cases it was found to be close to 

 the nucleus, while in others it was somewhat removed from the 

 same (see figures). 



The contents of these disks were finely granular, but, so far as 

 I could make out, the latter were not radially arranged. The outline 

 of the disks were clearly defined, and immediately surrounding the 

 latter, clear spaces could be seen under proper focussing 

 (Fig. 21), Within these disks and at about their centre , two or 

 three small granular bodies werepresent which stained 

 much deeper than the surrounding granules and which I 

 have taken for centrosomes (Mikrocentrum). 



In the cytoplasm of the cell immediately surrounding the disks, 

 the small chromophilous granules were arranged much closer to each 

 other than those more remote, but, so far as could be seen, this 

 arrangement was not a radial one. In consequence of this close 

 arrangement of granules, this region of the cell body stained much 

 darker than the disk. 



Such are the general appearances presented by these structures 

 as observed by me, and it cannot be denied that they bear a close 

 resemblance to what are commonly recognized in other cells as centro- 

 somes and spheres. 



The material in which these structures were best seen to ad- 

 vantage was fixed in Flemming's solution and stained in iron-haemato- 

 xylin. They were also found in sublimate preparations when stained 



