(_'amkj:()X. — X (pJiridi inn of Mntnidrilus losac Jh<l<l<n(l. 181 



tubule which counects them conespoud.s to the short " ciliated middle 

 tube " of Lii))ihricus, or the " bridge canal '" of Kisen. The third fold, or 

 " spur '" (^p). represents the third loop of Liniihricus, in which genus it is, 

 liowever, much longer. In Mdoridrihis \t -s short and curved outwards^ 

 and lies approximately at right angles to the posterior fold (sp). The nephro- 

 stomial duct, after passing backwards through the septum, traverses the- 

 body for a short distance, and joins the ventral end of the anterior fold 

 at the point where the outlet-duct leaves it. This latter duct lies parallel 

 to the folds and anterior to them : it crosses the coelom independently, 

 and enters the bladdei-. 



The shape of the bladder, or the muscular duct, differs in accordance 

 with the position of the nephridium. In the ventral series it ^s long 

 and straight, somewhat club-shaped, and comparatively narrow (fig. 2, bl). 

 At its inner end it bends down into the intermuscular gap of the body- 

 wall through which the chaetae (ch) project, and opens at this point to 

 the exterior. The pore is terminal, and the outlet-duct enters it at about 

 the middle of its length, or slightly nearer the dorsal end. The extension 

 of the bladder beyond the point of entrance of the outlet-duct I have callc<l 

 the caecum (fig. 2, eaec). 



In the dorsal Series, however, the bladder appears to be a direct con- 

 tinuation of the outlet-duct, very nmch enlarged (figs. 2, 6). It is wider than 

 the ventral bladder, but not so long. It is continued beyond the pore as a 

 short dilated caecum (caec). 



The nephridia lie practically fieely in the body-cavity, being joined bv 

 blood-vessels and occasional delicate strands of connective tissue to the 

 body-wall. There is no trace here of the large coelomic sacs or peritoneal 

 masses on which the nephridia of some earthworms are supported. 



The description given above refers to the nephridia from about the 

 middle of the length of the worm. There is no alteration of form, bevond 

 details of the coiling of the folds, towards the posterior end, though the 

 muscular bladder appears to become larger in comparison with the folds ; 

 nor is there any deo'ease in size of the nephiidia, which occupy, therefore, a 

 greater part of the cavity of the segments, which are smaller at this end of 

 the worm. The septa in this region are greatly thickened, and oliscure a 

 general view of the nephridia. 



In Muoridrilits there are no proctonephridia. Their absence was esta- 

 blished by examination of a series of horizontal sections through the pos- 

 tei-ior end of the worm. Fig. 11, taken from such a series, shows the opening 

 to the exterior of the third nephridium from the posterior end. There is 

 no trace of a longitudinal duct connecting the terminal portions of the 

 posterior nephridia. and opening by one common opening into the ali- 

 mentary canal, such as has been lecorded by Beddard (6). who discovered 

 the anal nephridia of OctochaetuN iindtiporHs, and found that they opened 

 not only to the alimentary canal, but also to the exterior, and in each case 

 by many pores, as is characteristic in that genus. 



I could not find in the wall of the rectum of Maoriilrlhis any indication 

 of a network of nephridial tubules opening by intercellular duets into ita 

 cavity. 



The nephridia of the clitellar region are similar to those of the post- 

 clitellar. In the ])reclitellar region, and particularly in the fii-st six seg- 

 ments, the nephridia are much larger, and present a distinctly different 

 appearance (figs. 7 and 8). In Segments 3-6 the septa, being inclined back- 



