Smallwood, Molluscan Nerve Cells. 185 



There are located in the cerebral, pleural, pedal and visceral 

 ganglia of most gastropods a few nerve cells much larger than those 

 that make up the bulk of the ganglion. In Helix, Doris, Aplysia 

 and others these are of enormous size. The small nerve cells are 

 too small for a satisfactory study, so one is limited in the main to 

 the few large cells in each ganglion. 



All of the text figures were drawn with a camera lucida, the ~ 

 oil immersion and two-inch ocular, Bausch and Lomb. 



In Fig. I, flthereare two conspicuous 

 lymph spaces and four smaller ones. 

 These are not connected with one 

 another or with the surrounding neu- 

 roglia cells. The cytoplasm is quite 

 uniformly granular. The nucleus is 

 sharply defined by a membrane and 

 the larger size of its granules. On the Fig. i. 



side toward the axone, the nuclear membrane is sharply bent in 

 toward the center of the nucleus and the larger granules assume 

 a radial and beadlike arrangement as if there were some marked 

 physiological activity taking place. In Fig. i, b the lymph spaces 

 are smialler and more evenly distributed. The cytoplasm differs 

 from the conditions in Fig. i, a in that there are several rodlike 

 and granular bodies present. These bodies take the same kind 

 of a stain that the large granules in the nucleus of each cell 

 takes. In one instance the granules of the cytoplasm were 

 arranged radially around one of the rodlike bodies having very 

 much the appearance of a centrosome and sphere. McClure 

 ('97) describes similar conditions in gastropod nerve cells and 

 explains them on the ground of the persistence of the centrosome 

 and sphere. 



It is further to be noted that the granules in the nucleus have the 

 same radial, beadlike arrangement around the infolded nuclear 

 membrane. These granules are very noticeable because oi their 

 intense react;on to basic stains. The nucleolus is solid and large; 

 a single one is figured in this section, but as many as seven have 

 been counted in some nerve cells of Haminea. These two nerve 

 cells were taken from the same animal which was fixed with picro- 

 acetic (Boveri) under normal conditions. 



Venus. — A large number of preparations of the visceral gan- 

 glion of the common market clam were made in the hope that the 



