362 MOORE. [Vol. XIII. 



The discodrilid nephridium has probably no other than an 

 excretory function, there being no evidence that it may be 

 respiratory, though the fluid which it carries off is probably 

 more or less laden with carbon dioxide. The statement by 

 Mcintosh (26) that in Branchiobdella the posterior nephridia 

 serve as oviducts is probably without foundation, as no more 

 unsuitable conductor for the large ova could be imagined than 

 the narrow tortuous tubes ; besides they have no communica- 

 tion with the ovarian somite, and the true ovipores are easily 

 demonstrated. 



It now remains to compare the discodrilid nephridium with 

 its homologue in other annelids. It is unnecessary to consider 

 the Polychaeta, with their short wide tubes. On comparing 

 typical nephridia of Hirudinea and Oligochaeta, the resemblance 

 between the two is remarkable ; and this is true whether we 

 compare the plectonephridia of the fish leeches Pontobdella, 

 Piscicola, and Branchellion with those of such Oligochaeta as 

 many of the Acanthodrilidae, Perichaetidae, and Cryptodrilidae, 

 or the meganephric condition of the leeches possessing more 

 specialized coeloma with that of Lumbricus, for example. The 

 second type alone concerns us here, and we may select for com- 

 parison Bourne's (11) figure of Clepsine and Benham's (6) for 

 Lumbricus. Omitting details we find that in the body of the 

 nephridium the entire tubule system of Clepsine corresponds to 

 the middle loop alone of Lumbricus, the main lobe of the former 

 being the anterior, the apical lobe the posterior, limb of that 

 loop. At the apex of the apical lobe of Clepsine both the wide 

 and narrow tubules bend back, the latter returning on itself, 

 the former passing from the main lobe into and down the api- 

 cal lobe. Now if this apex be imagined as greatly produced, 

 we shall have four tubules lying side by side and corresponding 

 exactly to the third or posterior loop of Lumbricus, which is 

 nothing but the greatly developed apex of the apical lobe. The 

 connecting tubule or bridge between the apex of the apical lobe 

 and the main lobe of Clepsine is represented in Lumbricus by 

 the point where the narrow and middle tubules meet. The 

 perforated cells of the main lobe of Clepsine are evidently 

 enlarged drain-pipe cells which have secondarily enclosed the 



