212 



GRAF. 



[VOL. I. 



variable. In some species it lies in the ventral lacuna near 

 the ganglionic chain; in others it is situated in a lateral pouch 

 of this ventral lacuna; in others it still lies ventrally in the 

 so-called intermediate lacuna (Zwischen lacune) of Oka; and, 

 finally, it may assume a dorsal position in a coelomic section 

 near the lateral lacuna. 



In Clepsine Hollensis the funnels of the anterior segments 

 lie near the ventral lacuna, whereas in the posterior segments 



100 



they lie dorsally, very near the lateral lacuna; a fact which 

 would imply that the more primitive position is the ventral 

 one. 



The other part of the nephridium of both genera consists -of 

 a chain of cells possessing a different structure in different 

 parts. 



The portio afferens-glandulosa, the innermost cells of which 

 stand in close contact with the receptaculum (not in open com- 

 munication, however), is characterized by an intricate network 

 of vacuoles and canals filling the cells of that portion. The 

 portio glandulosa-efferens is pierced by a single central canal 

 only. Both portions are covered with a connective-tissue 

 membrane. 



The whole course of the nephridium with all its intricate 

 windings and loops was outlined with the help of the camera 

 lucida from a very young specimen of Clepsine Hollensis lightly 



