AN'ATOMY OF nOLOTHWRIANS. 129- 



on one side arises the " respiratory tree," which has but one 

 main stem, and is only occasionally held in place by mus- 

 cular threads. The branches are numerous, and are smaller 



Pig. 89. — Pentacta frondosa. ^, tentacles; I, ioiigitndinal muecles: r, retractor mus- 

 cles of the teutacular system; i, intestine; c. cloaca-,^ &, respiratory tree; vr, water- 

 vascular ring or ring-canal, v, radml water- vascular canal; m. madreporie body; pp^ 

 polian vesicles; am, ampullEe; a, a', pseudo-hsemarcontractile vessels (from C^rus);, 

 0, ovary; ov, jviduct. — Drawn/ by J. S. Kiugsley from a dissectiou made by the author. 



and paler than the ovarian tubes. The water enters the 

 cloaca (c), passes into the respiratory tree {b), oozes out of 



