222 LANGDON. [Vol. XL 



Isolated nerve-cells. — Kulagin ('88) described in the epider- 

 mis of several species of Lumbricus isolated sense-cells with a 

 hair projecting through the cuticula and a base connected with 

 a nerve fibre. As he gave no figures, and apparently did not 

 use a specific nerve-stain, it is impossible to decide on the 

 character of these cells. Lenhossek (-92), believed the sensi- 

 tiveness of Lumbricus to be due to isolated nerve-cells which 

 were scattered " an alien Stellen der Korperoberflache mit Aus- 

 nahme der intersegmentalen Furchen." He stated that these 

 cells "finden sich weder auf gewisse Gegenden beschrankt, 

 noch an bestimmten Stellen zu besonderen Sinnesorganen 

 angehauft, sondern erscheinen iiber alle Gebiete der Epi- 

 dermis gleichmassig vertheilt." I have been unable to dis- 

 cover any isolated nerve-cells. I have found many cells which 



tributed over a metamere. His " vordere Giirtel " is not near enough to the inter- 

 segmental groove to correspond to my " cephalic zone." The different results we 

 have arrived at in regard to the distribution and numbers of the sense-organs is 

 due to the fact that my study was made by means of the cuticular spots and his 

 by means of sections. In the latter the cephalic zone, the nephridial group, and 

 many of the smaller organs are apt to be overlooked. (3) Hesse believes that the 

 two ventral rami of a nerve-ring meet in the mid-ventral line. I have never found 

 this to be the case. He found that the dorsal rami of the anterior and posterior 

 nerve-rings always remained between the two muscle-layers. I have found that 

 all three rings pass into the circular muscle-layer during the last part of their 

 course dorsally. (4) Hesse describes groups of ganglion-cells in the course of the 

 nerves of the prostomium. In discussing their function, he considers it probable 

 *' dass die sensiblen Fasern die von den -Sinneszellen aufgenommenen Reize an die 

 Ganglienzellen iibermitteln, deren motorische Fortsatze an die Ruckziehmuskeln 

 der Oberlippe fiihren und deren Zusammenziehung veranlassen," but he has &\\- 

 dently not been able to trace these fibres. I have been able to find ganglion-cells 

 which seem to be the same as those which he describes, but it does not seem to 

 me that the fibres from the sense-organs end among these cells. In the course of 

 the nerve-rings, Hesse has "nur einmal eine solche beobachtet, und zwar eine 

 bipolar." My haematoxylin and silver nitrate preparation have not shown such 

 ganglion-cells in the nerve-rings, but some alum carmine mounts which I have 

 lately examined have revealed them in considerable numbers. I counted the number 

 of these ganglion-cells in one half of each nerve-ring in the first thirteen metameres 

 of one worm. The second metamere had but one on its median ring ; the third 

 had one on its anterior ring and four on its posterior ring. From the third 

 through the thirteenth, the ganglion-cells occurred in every nerve-ring in num- 

 bers varying from two to eight. I could see that these cells were bipolar, and in 

 several cases that a fibre started both towards and away from the central nervous 

 system. I e.xpect to continue my work on these ganglion-cells and to give more 

 concerning them in the future. 



