ANATOMY OF HOLOTHURIANS. 



211 



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 



.__. .. 

 Cles of the t( 

 vascuh 



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

 0, ovary ; ov, oviduct. 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 



