.*>70 MR FRANK E. BEDDARD ON THE ANATOMY OF OCNERODRTLUS. 



elements of two kinds : firstly, large clear cells (b) with a deeply stained nucleus and a 

 very evident limiting membrane ; and secondly, small granular deeply staining cells (a). 

 The latter I believe to be simply perivisceral corpuscles which have become attached 

 to the mass of hyaline cells. They agree in every particular with cells found floating freely 

 in the perivisceral fluid. 



The mass of clear cells partly surrounding the nephridia are no doubt modified 

 peritoneal cells, which correspond to the similar cells which arc found in connection with 

 the nephridia in the Lumbriculidse, Phreoryctidse, and some other aquatic Oligochseta. 

 Among Earthworms, Pontodrilus is furnished with similar cells. This discovery was made 

 by Perriee [21], and is justly regarded by him as a point of affinity between Pontodrilus 

 and some of the lower Oligochseta. Perrier's figure [21, pi. xiv., fig. 11] does not repre- 

 sent the microscopic appearance of these cells very well if they are exactly like those of 

 Ocnerodrilus. Another point of resemblance between Pontodrilus and Ocnerodrilus is 

 the commencement of these cellular masses round the nephridium in the XlXth {Ponto- 

 drilus) or XXth [Ocnerodrilus) segment. But in Pontodrilus there are no nephridia 

 before the XV th segment, whereas in Ocnerodrilus these organs commence in the Illrd. 



I have stated that there are no nephridia in the Xlth and Xllth segments. 



The Xllth segment is very much reduced as compared with the neighbouring seg- 

 ment. On each side of the body it is occupied by a mass of cells, perfectly independent of 

 the alimentary tract, which is illustrated in fig. 10 of the plate. This mass occupies nearly 

 the whole of the available space, and towards the dorsal side of the body (the right 

 of the figure) completely fills the segment from side to side ; ventrally the mass of cells 

 becomes narrower, and is bent upon itself. The bending is not shown in the figure. The 

 cells of which this body is formed are of two kinds, which it is unnecessary to describe 

 further as they agree perfectly with the cells surrounding the nephridia of the posterior 

 segments. In the Xlth segment is a similar mass, which is, however, much smaller. 



These bodies seem to me to represent the last trace of the nephridia of the Xlth and 

 Xllth segments. This is probably accompanied by an increase in the number of the 

 clear peritoneal cells which exists in the following nephridia, though they are very few 

 in number as compared with the nephridia of the posterior segments. There is, in fact, 

 not a complete change, as in Pontodrilus, between the anterior and posterior sets of 

 nephridia. I could find no hyaline cells attached to the nephridia of the first three or 

 four segments ; but from this segment to the XXth a few such cells were present ; and I 

 believe that the peculiar bodies of the Xlth and Xllth segments are simply due to a 

 proliferation of these cells after the disappearance of the nephridium. 



The funnels of the nephridia are small and composed of comparatively few cells. One 

 side of the funnel (see fig. 11) is considerably longer than the other; the cilia are well 

 developed. As the nephridia of segments XI and XII are rudimentary, I was naturally 

 unable to find any nephridial funnels depending into the Xth and Xlth segments. Nor 

 did I succeed in observing any nephridial funnel attached to the posterior wall of segment 

 XIII. The nephridia of segment XIV, however, are present and well developed. From 



