164 
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 agree 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 spaces so that the ventricle in section has 
a somewhat spongy appearance (fig. 59). 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 cheetigerous annuli, just 
dorsal and posterior to the neuropodia, 
fach nephridium may be divided into three regions, 
an anterior funnel or nephrostome,* 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 celom 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 lp 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, 
