76 Dr. R. P. Cowles on the Body-cavjtiea and 



Yvr. 5. 



Fig. 4. — Longitudinal section through larva with two tentacles, X 704. 

 c.c, coUar-cavity ; c.t.r., ciliated tentacular ring ; y., ganglion ; 

 m}, mesentery between lobe- and collar-cavities : x., indication 

 of a mesodermal sac. 



Fig. 5. — Longitudinal section through an Actinotrocha from Beaufort 

 Harbour, x 112. o.c.c, adult collar-cavity ; h.c, blood-cor- 

 puscles ; c.c, larval collar-cavity ; d.m., indication of dorsal 

 mesentery; ^.i'., dorsal blood-vessel ; g., ganglion; m.^ mesen- 

 tery between lobe- and collar-cavities ; m.^, mesentery between 

 collar- and trunk-cavities ; p.o.c, preoral body-cavity ; p.r. peri- 

 anal ring ; ^.s., perianal sinus ; sen.p., sensory papilla; t.c, trunk- 

 cavity ; v.m., ventral mesentery' ; v.p., ventral pouch. 



