140 ZOOLOGY 
and an intestine. On the ventral wall of the oesophagus a 
U-shaped tube opens; one limb of this tube is enormously en- 
larged, and is very muscular. A somewhat 
similar stomodaeal musculature occurs in 
the pharynx of most Chaetopods, and would 
seem to be comparable to the odontophore 
of Molluses, and with the ventral part 
of the muscular pharynx in Turbellarians. 
The intestine is moniliform, there being a 
constriction between each segment. It is 
supported by the transverse septa and by 
median dorsal and ventral mesenteries (Fig. 
90). Its lumen is ciliated. The anus is 
terminal. 
The vascular system consists of a 
median dorsal vessel, which sends a 
branch along each tentacle. Other 
branches bring the colourless blood back 
from the tentacles, and these then fuse to 
form the median ventral vessel. Certain 
lacunae between the epithelial cells of the 
intestine and its musculature appear to 
Fic. 88.—View of a ne- Supply the dorsal vessel with the fluid it 
phridium of Protodrilus eontains. 
Leuckartii. After Hat- 6710 : : 
schek. The nephridia consist of an internal 
1. Internal opening funnel (Fig. 88), from the edge of which a 
3 i ee large cilium depends into the lumen of the 
3. Cilia of anterior ring tube which is ciliated ; this passes through 
of the segment. . a0 5 
4. Cilia of posterior &® Septum, as in ZLumbricus, and finally 
ring of the seg- opens to the exterior on the lateral line. 
5. Basin The nervous system remains in the 
skin (Fig. 90); it consists of a cerebral 
mass, with circum-oesophageal commissures, which pass into 
two ventral cords. The latter are separated from one 
another by the ventral groove, but are connected by trans- 
verse commissures. 
Protodrilus is hermaphrodite, Polygordius dioecious; the 
ovaries lie in the first seven segments. The ova are derived 
from some of the cells lining the coelom in the neighbourhood 
