302 MR FRANK E. BEDDARD 



as well as in a number of minor points which need hardly be recapitulated, as they 

 are found in many of the aquatic Oligochaeta. I refer to such points as the shape and 

 arrangement of the setae, the absence of gizzard, &c. The five points of agreement 

 between Pelodrilus and Phreoryctes enumerated above are stated in such a way as to 

 refer only to the families of aquatic Oligochaeta ( " Limicolce " in the sense of Claparede), 

 which I consider alone for the present. The more important points of difference between 

 Pelodrilus and Phreoryctes are these : — 



1. Sperm ducts greatly coiled ; both on each side opening upon the Xllth segment, 

 though separately. 



2. Only one pair of ovaries in XII, and one pair of oviducts opening between 

 XII/XIII. 



3. The presence of septal glands. 



4. Nephridia present in some of the genital segments. 



5. Clitellum occupying only three segments (XI-XIII), and developed only ventrally ; 

 setae of segment XII absent. 



6. Some of anterior septa thickened. 



These structural characters of Pelodrilus do not indicate much affinity to any other 

 group of the lower Oligochaeta. The Lumbriculidae are the only other group with 

 which any comparisons suggest themselves, and these are really limited to the 

 characters of the setae, and of the oviduct, which has pretty much the same form. It 

 is true that Lumbriculus is the only other genus of aquatic Oligochseta where the 

 nephridia persist in the genital segments ; but this fact, though important enough in 

 another aspect, is, perhaps, hardly one upon which considerations of affinity can 

 be based. 



The greatly coiled sperm ducts recall those of the Tubificidae and Enchytraeidae, 

 but other characters do not permit of the establishment of any close relationship 

 between Pelodrilus and either of these two families. 



On the other hand, it does seem possible to indicate some relationship between 

 Pelodrilus and the higher Oligochaeta (earthworms), though these are not sufficiently 

 pronounced to admit of a comparison between Pelodrilus and any particular family 

 or families of that group. 



The general resemblances to the higher forms, other than those shared by 

 Phreoryctes, are as follows : — 



1. Persistence of nephridia in certain of the genital segments. (This is shared by 

 Lumbriculus.) 



2. Several of anterior intersegmental septa greatly thickened. 



3. One of the pairs of vasa deferentia traverses two segments between the internal 

 and external orifice. 



Phreoryctes itself comes nearer to Earthworms than does any other genus among 

 the lower Oligochaeta, and Pelodrilus serves to increase the closeness of the family 

 Phreoryctidae to the higher Oligochaeta. 



