296 MR FRANK E. BEDDARD 



In such preparations the nephridia are seen to occupy a relatively small space in the 

 body cavity of their segment ; each lies coiled up closely approximated to the anterior 

 septum ; the duct to the exterior passes off from the ventral surface of the nephridium, 

 and after a relatively long course opens on to the exterior in front of the ventral pair of 

 setae. This position in front of the ventral pair of setae is also found in Phreoryctes [12], 

 though apparently not in Phreoryctes filiformis, and in Phreatothrix among the 

 Lumbriculidse. 



The nephridial funnel, as in all Oligochseta in which there are paired nephridia, except 

 Plutellus, lies in the segment anterior to that in which the nephridia itself is placed. A 

 single funnel depending into the IXth segment is shown in fig. 24 ; they lie near to 

 the junction of the septum with the body wall, on a level with the ventral setae. 



A single nephridium in situ is illustrated in fig. 2. The coils of which it is composed 

 are closely pressed together, and under a low power it looks almost as if the nephridium 

 were simply formed by a comparatively short and broad tube bent a few times upon 

 itself. A closer examination shows that each coil is really composed of a bundle of fine 

 nephridial tubules closely pressed against each other, and occasionally anastomosing. They 

 run for the most along or at right angles to the long axis of the mass. There is hardly 

 any development of peritoneal cells round the nephridia ; certainly the large vesicular 

 cells, which are so often found in the aquatic Oligochseta, are absent. 



§ Body Cavity. 



The septa which separate the ccelom into a series of cavities corresponding to the 

 external segments are replaced in the four anterior segments by irregularly- placed fibres 

 and bundles of fibres passing between the alimentary tract and the parietes ; after the 

 Vth segment the regular septa begin. It is interesting to find that the first five of these 

 are very thick, and consist of two distinct muscular coats, whose fibres run in opposite 

 directions. The relative thickness of one of these anterior septa, as compared with one 

 of those that immediately follow, will be seen by a comparison of figs. 25 and 26, which 

 were drawn with the aid of a camera lucida. The septa are cup-shaped, with the concavity 

 directed forwards, and in the segments which contain the sperm sacs and ovisacs this con- 

 cavity is much emphasised by the stretching of the septa, caused by the growth of the 

 sacs in question. 



As far as I am aware, Pelodrilus is the only instance of an Oligochset, which Claparede 

 would undoubtedly have referred to his group of Limicolse, where this increase in thick- 

 ness of the anterior intersegmental septa is met with. It may very possibly have 

 a relation to the habitat of the worm in soil, and not in the softer mud at the bottom 

 of a lake or river ; and in any case it shows that no importance can be attached to the 

 presence of these thickened septa in Earthworms as a character distinguishing them from 

 the lower Oligochseta. In view, however, of other points in which Pelodrilus resembles 

 the higher Oligochseta, this character, perhaps, gains an additional importance. 



