OLIGOCHAETA. 



499 



winding tube, in which the following regions can be distinguished 

 (Fig. 407): (1) the preseptal 

 portion consisting of the coelomic 

 funnel and a short tube (a), lead- 

 ing back to the septum which it 

 perforates, to become continuous 

 with (2) the rest of the nephrid- 

 ium, which lies in the segment 

 behind. This postseptal part 

 presents the following regions : 

 (b) the narrow tube of consider- 

 able length and thin wall; parts 

 of it are ciliated : (c) the mi<hlk' 

 tube which is short and confined 

 to the length of one loop only ; 

 the middle tube is ciliated : (d) 

 the wide tube, which is long, 

 non-ciliated, and opens into a 

 short, dilated, muscular - walled 

 portion the muscular duct which 

 opens to the exterior through the 

 ventral body-wall. The whole 

 nephridium, except the muscular 

 duct and the funnel, consists of 

 the so-called perforated or drain- 

 pipe cells. 



In the Limicolae the nephrid- 

 ium is generally simpler, consisting 



FIG. 407. Nephridium of Lumbricus (from 

 Vogt and Yung, after Gegenbaur). a funnel 

 and preseptal portion ; b the narrow tube ; 

 c the middle tube ; d the wide tube ; e the 

 muscular duct. 



Fic. 408. Section through a loop of the nephridium of 

 Lumbricus (after Claparede, from Vogt and Yung), showing 

 the perforated cellular character ; a nuclei ; b lumen ; c 

 blood vessel; d connective tissue. 



of the funnel (pre- 

 septal) and a long 

 coiled duct, passing 

 through a protoplas- 

 mic tube or mass in 

 which cell limits are 

 not always discernible 

 (Fig. 409), and lead- 

 ing to the wider ter- 

 minal part. 



As a rule there 

 is only one pair of 

 nephridia in each 



