142 Transactions. — Zoology. 



body is straight and of some thickness ; the free portion is 

 slightly curved, and tapers gradually towards its extremity. 

 Each of these setae was invariably accompanied by two reserve 

 seta? of the same form, one on each side. In no instance did 

 I observe more than a single mature seta belonging to each of 

 the two dorsal series. On the other hand, the ventral setae 

 were as invariably paired. The setae of the ventral series are 

 of two kinds ; a single set of each kind are found in every pair. 

 In both cases the setae approximate in shape to those of the 

 LumbriculidcB and of earthworms ; the extremity is not bifid, 

 and shows no traces of having been worn down. The 

 imbedded portion of the setae is nearly straight, but the free 

 portion is much curved — more so than in the setae of the two 

 groups referred to. This, however, only applies to the larger 

 of the two setae in each pair ; the smaller seta has a less- 

 marked curvature. I could observe no difference in the setae 

 in the different regions of the body ; but, as the worm was not 

 fully mature, it does not follow that such differences may not 

 be developed later. In every case the setae protruded from 

 the apices of well-marked papillae. The prostomium is obtuse, 

 ending in a wide truncated anterior margin. The clitellum 

 was visible in neither of the two specimens. The male genital 

 apertures are paired, and lie on segment xii., in front of the 

 ventral setae. The oviducal yores occupy a corresponding 

 position in the interval between segments xii. and xhi. The 

 spermathecal pores lie in front of the dorsal setae of seg- 

 ment xiii. 



" Integument. — The integument had the same structure 

 throughout. In neither of the two specimens which I ex- 

 amined was the clitellum developed, nor was there the very 

 least indication of the position of this organ, such as is some- 

 times afforded in immature Oligochceta. It is evident, there- 

 fore, that Phreodrilus, like some other genera, may reach a 

 considerable degree of sexual maturity of the internal organs 

 without a corresponding development of the clitellum. 



" Nephridia. — These organs commence only in the four- 

 teenth segment (in the worm with sexual organs) ; the whole 

 organ is furnished with the large vesicular cells so commonly 

 found attached to the nephridia of the lower Oligochceta. The 

 funnel opens into the segment in front of that in which the 

 organ lies ; it is small, and is placed to the side of the nerve- 

 cord. 



"Alimentary Tract. — As no known genus of the aquatic 

 Oligochceta possesses a gizzard," it is almost unnecessary to 

 state that Phreodrilus, which would certainly have been in- 



* "The so-called gizzard of the Naiclomorplia seems to be hardly corn- 

 parable with the gizzard of earthworms." — Beddard. 



