ANATOMY OF HOLOTHURIANS. 



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 



r 1 



HS&, =**> i CFS3S 



^^A^2^ilSL^^-B r~rrt-> 



,nr. 

 ..vr. 



..._\.. -a, 



Fig. 89. Pentacta frondosa. t, tentacles; I, longitudinal muscles; , retractor mus- 

 cles of the tentacular system; i. intestine; c. cloaca-, 6, respiratory tree: IT, water- 

 vascular ring or ring-canal, v, radial water-vascular canal: m. mad reporic body: pp, 

 poliau vesicles; am, ampullae; a, a', pseudo-haemal contractile vessels (from Carur-i; 

 0, ovary ; ov, i\iduct. 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 



