ANATOMY OF ROLOTRUBIANB. 



139 



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 



Fig. 89.—Pentactafr(mdosa. <, tentacles; I, longitudinal muscIeB; r, retractor mus- 

 cles of the teutacular system; i, intestine; c, cloaca-, ft, respiratory tree; it, water- 

 vascular ring or nng-canal, v, radial water-vascular canal; m. madreporic body; pp, 

 polian vesicles; am, ampullae; a, a', pseudo-haemal contractile vessels (from Carus); 

 0, ovary; ov, JViduct.— Drawn by J. S. Kiugsley from a dissection 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 



