STRUCTURE OF UROCH^ITA AND DICHOGASTER. 259 
believe, from the analogy of Urochseta, that it is branched. 
This nephridium terminates in a comparatively wide, thick- 
walled tube, which becomes wider and thinner walled as it 
approaches the external orifice, which is within the 
buccal cavity, as in the two species of Acanthodrilus 
mentioned above. In the segments of the body which follow 
(I am uncertain how many), the nepliridial system is much 
like that of Acanthodrilus multiporus; that is, it consists 
of tufts of tubules which open by numerous apertures on the 
surface of the body. These apertures have no regular 
arrangement that I could observe; frequently they are 
situated near to the setae, but as frequently they open near to 
the anterior or posterior boundaries of the segment. The 
apertures are extremely obvious, both in transverse and longi- 
tudinal sections, on account of their large size. I have not 
been able to observe any funnels connected with these ne- 
phridia. 
In the posterior region of the body the nephridia are 
different, and, as already mentioned, are in certain respects 
more modified than those of the anterior segments. 
On a dissection of this region of the worm the nephridia 
appeared to be separable into a number (about six) of pairs of 
distinct nephridia. In transverse sections the nepliridial 
system was seen to consist of scattered tufts of tubules aud of 
a large pair of nephridia ; the arrangement being, in fact, 
much like that of Megascolides. The calibre of the large 
nephridia was many times greater than that of the small tufts, 
or about equal to that of the nephridia of such types as Lum- 
bricus. Each of these large nephridia is furnished with a 
large ciliated funnel, which lies in the segment in front. I 
have been quite unable to detect the external apertures of the 
nephridia of these posterior segments. 
The tufts of smaller tubules were not in all cases (if in any) 
detached from the large nephridia ; their apparent distinctness, 
when seen in a dissection of the worm, is due to the fact that 
they are for the most part embedded in the centre of a mass 
of peritoneal cells. These peritoneal cells, which form aggre- 
