KAND : NEEVOUS SYSTEM OF LUMBEICID^. 109 



than they do in the preparations. In most cases it required the most 

 careful focussing and varying of illumination to bring out the less 

 distinct radiating fibrillse. 



IV. Observations. 



1. The Nerve Cells op Lumbricid^. 



My 6rst study to ascertain the condition of the nerve cells of the 

 earthworm was made upon normal unregenerated material tixed in 

 sublimate and stained in iron-hsematoxylin. Some evidences of con- 

 centric and radial cytoplasmic structure were found, suggesting the 

 presence of structures which might be brought out more clearly by 

 better methods. 



In transverse sections of the ventral ganglia the greater number of 

 ganglion cells are cut in planes parallel to their long axes. The cells 

 are situated ventrally and laterally in the cord. They are unipolar 

 and pear-shaped, the larger ends being peripheral, while the processes 

 extend dorsally and centrally. The nuclei, with extremely rare excep- 

 tions, are situated in the process end of the cell, often so far toward 

 that end that the nuclear membrane is tangent to the tapering sides of 

 the cell. The diameter of the nuclei varies from 6 fi to 16 fi. The 

 cells are from 22 /x to 60 /x in length, and from 10 |U to 28 /i in transverse 

 diameter. 



The nuclei are always nearly or quite spherical and never invaginated. 

 In the resting nerve cells of many animals where the centrosome has 

 been found the nucleus has been described as invaginated, the centro- 

 some occurring in the cytoplasm on the invaginated side of the nucleus. 

 The position of the nuclei in the nerve cells of the earthworm is such 

 as to leave by far the greater mass of cytoplasm on that side of the 

 nucleus opposite the nerve process. 



Early in ray study of these cells I was impressed with the fact that, in 

 a large number of them, more or less irregular small masses of deeply 

 stained material occurred near the nucleus and on the side of it toward 

 the centre of the cell. If a line through the centre of the nucleus and 

 the centre of the cell be called the axis of the cell, these masses occurred 

 in or near the cell axis. Occasionally faint radiations could be detected 

 coming from the region of the central masses just mentioned and extend- 

 ing toward the periphery of the cell. 



A more careful study of later and more favorable preparations 



