244 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



forming a mass loosely filling the process (figs. 33 and 40). 

 The granules in the cells are in some cases united into a 

 spherical mass lying in a vacuole ; in others they are 

 minute and scattered. They agTee in appearance with 

 the chlorogogen granules of the peritoneum. These in- 

 growths begin and are throughout best seen upon the 

 posterior (and to some extent on the outer) wall of the 

 heart. In large specimens they encroach on the cavity of 

 the ventricle to such an extent as to sub-divide it into a 

 large number of sjDaces so that the ventricle in section has 

 a somewhat spongy appearance (fig. 39). The heart body 

 appears to be a means of preventing regurgitation of the 

 blood into the gastric plexus after systole, and of ensuring 

 its passage into the ventral vessel. The presence of the 

 chlorogogen granules suggests that it may also have an 

 excretory function. 



Nephridia. 



There are six pairs of nephridia which open to the 

 exterior on the fourth to the ninth chaetigerous annuli, just 

 dorsal and posterior to the neuropodia. 



Each nephridium may be divided into three regions, 

 an anterior funnel or nephrostomy,* a middle secreting 

 portion and a posterior vesicle or bladder. 



The funnel is always bright red in colour owing to its 

 rich vascular supply. It opens into the ccelom by an 

 elongated slit-like aperture which is generally directed 

 forwards and inwards and is bordered by two lips which 

 may be described as ventral and dorsal. The ventral lip 

 is entire and almost semi-circular. The dorsal lip is 

 slightly larger and fringed by ciliated, vascular processes 

 placed close together on the edge of the lip (figs. 24 and 



-'- See also under Post Larval Stages, p. 68, 



