EXPLANATION OF PLATE VIIl. 



^OI^OSOMA, Sp. 



Fig. I. — General view of the animal seen by transparency from 

 the ventral surface. The blood-vessels are shown in 

 their anterior portions only, and nephridia only on one 

 side. 



Fig. 2. — Side view of the posterior portion of a chain. 



Fig. 3. — Head and oesophageal region, more highly magnified, 

 seen by transparency from the ventral surface. 



Fig. 4 a and h. — Two forms of the cerebral ganglion. 



An., Anus ; c, cells round oesophagus ; con., constriction 

 between successive members of a chain; d.v., dorsal vessel, seen 

 through the superficial structures ; /., intestine ; /.,lip; w., mouth; 

 «', n\ n\, first, second and seventh nephridia ; n.g., nerve gang- 

 lion ; 0., oil-cell ; ce., oesophagus ; f)h., pharynx ; fr., prostomium ; 

 s., setai ; s.h., sensory hairs; sp., septum; s.s., setal sac; st., 

 stomach ; sir., strands uniting intestine and body-wall ; v. v., ventral 

 vessel, dividing to encircle pharynx. 



