114 EDWIN S. GOODRICH. 



grouped round a few intercellular canals, which open into 



the collar cavity by broad funnels The internal funnels, 



without doubt open into the collar cavities" (H). 



Menon, Avho gives a more correct figure of the excretory 

 cells, has likewise described internal openings to the neph- 

 ridia (13). 



A careful study of the nephridia of Actinotrocha in the 

 living, in teased preparations, and in sections has convinced 

 me that no such opening exists. The nophridial canal is inter- 

 cellular, has a narrow ciliated lumen, and opens by a small 

 external pore on the ventral surface some distance behind the 

 ring of tentacles. It passes forwards and inwards between 

 the ccelomic epithelium of the trunk cavity and that of the 

 pre-septal coelom (when the latter is developed) until it reaches 

 the anterior surface of the septum, and projects freely into 

 the large pre-septal blood space (figs. 5, 2, and 10). This 

 projecting portion of the nephridium does not appear to be 

 externally covered by a regular epithelium. The extreme 

 inner end of the nephridial canal expands considerably, while 

 its wall thins out into a mere membrane. It is this expanded 

 region which has been mistaken for an open funnel. On the 

 thin wall of the terminal expansion arc situated the excretory 

 cells, which are, in fact, typical solenocytes. 



Figs. 5, 6, 7, 8, and 15 illustrate the structure of the 

 solenocytes in the larvae from Faro. The cell-body is provided 

 with long, protoplasmic, free processes similar to those I have 

 described in Nephthys and other Polychgetes (6). The nucleus 

 is bent round so as to embrace the extremity of the tube 

 (figs. 7 and 8). Owing to this curved shape of the nucleus 

 the solenocytes often present the deceptive appearance of 

 possessing two or three small nuclei. The tube itself, which 

 is of a cuticular substance, staining blue with nigrosin, is 

 somewhat short and wide. It does not project into the lumen 

 of the nephridial canal as in the case of Amphioxus and 

 many Polychuctcs (6 and 8). A certain quantity of protoplasm 

 seems to extend down the tube from the cell-body on the 

 side on which the nucleus is situated. A loni>- flao-ellum is 



