364 MOORE. [Vol. XIII. 



Turning now to the Oligochaeta, we meet with a much 

 greater range of variation, but, omitting a few special cases, the 

 great majority of nephridia which have been described readily 

 fall into line. In reviewing the several families of earthworms 

 we may select a few typical genera for comparison, using those 

 in which the arrangement of the tubules has been sufficiently 

 described, though the finer structure is in most cases still 

 unknown. Among the Lumbricidae there is little departure 

 from the Lumbricus type except in Allurus (Beddard, 2), 

 which has simplified nephridia. Many genera of the Geoscoli- 

 cidae have two series of nephridia which differ somewhat ; the 

 anterior ones are frequently specialized, but the general arrange- 

 ment of the tubule is in two parallel loops, as in Rhinodrilus 

 (Thamodrilus) (Beddard, 3), and Criodrilus, (Collin, 13), or in a 

 tuft of loops, as in Pontoscolex (Urochaeta), (Perrier, 30). If 

 the remarkable integumental network of Libyodrilus (Beddard, 

 4) and related genera be disregarded, the paired nephridia of 

 the Eudrilidae are also of the two-looped type. (For Eudrilus, 

 see Horst, 22.) The Acanthodrilidae include worms with the 

 nephridia either paired or diffuse, the meganephric forms having 

 simple looped tubules, as in Acanthodrilus (Beddard, 5), Diplo- 

 cardia (Garman, 20), and Kerria (Eisen, 15). The latter is of 

 small size and the nephridial blood supply is wanting, which 

 may possibly also be the case in the large Diplocardia. The 

 Cryptodrilidae are much like the last family in nephridial char- 

 acters. Eisen has very carefully figured and described several 

 of the meganephric genera, — Pontodrilus (I6), Deltania (17), 

 and Argilophilus (17) having nephridia which in complexity of 

 tubule arrangement and blood supply rival or surpass Lumbri- 

 cus ; and Ocnerodrilus (is), which, while of no smaller size 

 than some of the above, has a single bent tubule loop and no 

 blood supply. 



Although the genera enumerated above are but a drop in 

 the bucket in these days of rapidly multiplying oligochaetous 

 genera, and are selected as a few typical examples, the writer 

 has examined a very large part of the published figures and 

 descriptions in coming to the following conclusions. Among 

 many of the higher worms the Lumbricus type is departed from 



