Cameron. — Nephrifliiim of Maoi-idrilus insao Bnhhird . ISo 



lies on the anterior or outer side of the anterior fold (a./), 

 and is straight : there is no branching of the narrow dnct 

 in Maoridrilus as there is in Microchaeta (Benham), in 

 Moniligaster (Bourne), and in Argilophilus figured by Eisen, 

 where the duct breaks up into a spongy mass of tubules 

 encircling the other canals. 



In the dorsal lobe {d.l), where the anterior and posterior 

 folds become continuous, the outer narrow canal commences 

 to loop round and wind in and out of the inner narrow canal 

 («.*). This looping often continues for a considerable dis- 

 tance down the posterior fold (p.f), though in the majority of 

 specimens examined it was restricted to the dorsal lobe. 



The outer narrow canal con- 

 tinues down the outer (pos- 

 terior) side of the posterior 

 fold, and enters the " spur," 

 in which it crosses over (at 

 point X, fig. 8) from the pos- 

 terior to the anterior side. 



At the apex of the spur the 

 duct turns back along the an- 

 terior or inner surface, and 

 without change of diameter 

 returns along the posterior 

 fold as the " inner " narrow 

 canal (a.i) lying parallel to 

 the " outer " canal. In the 

 dorsal lobe this part of the 

 canal is ciliated at certain 

 points. After the "windings" 

 in the dorsal lobe it is con- 

 tinued into the anterior fold, 

 where it passes across the wide 

 tube (c), and and comes to lie 

 on the inner side of the fold, 

 separated by the wide tube 

 from the outer canal. 



In some of the nephridia 

 examined the inner narrow 

 canal was, in this fold, of 

 slightly greater diameter than 

 the outer canal ; in the ma- 

 jority, however, both ducts 

 were approximately of the 

 same dimensions. 



At the point where the 

 nephrostomial duct enters the 

 nephridium — i.e., at the lower 

 end of the anterior fold — the 

 inner canal turns sharply back, 

 as shown in fig. 8, to form what 

 I have termed the " bridge " 

 canal (6). This does not lie in 

 either of the nephridial folda. 



Fig. 8. 

 An anterior dorsal nephridium from one of the seg- 

 ments 3 to 7, greatly enlarged, to show the course 

 of the nephridial canal through the various 

 folds. 



