'EESPIEATOEY TEEE.' 



205 



cloaca (fig. 101, e), contained within the cavity of the abdomen, to the 

 walls whereof it is attached by delicate fleshy bands : this cloacal cavity 

 communicates with the exterior of the body by a wide orifice twice as 

 large as the aperture of the mouth, through which, in the figure, a 

 bristle (/) has been passed ; and it is by this orifice that the water re- 

 quired for the purpose of respiration is taken in, and then forced, by the 

 muscular walls of the cloaca itself, through the whole system of respi- 

 ratory canals whereby its distribution is effected. The organs of respi- 

 ration commence at the upper part of the cloaca, near the termination of 



Fig. 101. 



Polian 



Anatomy of Holothuria : a, bristle inserted into the mouth; 5, inverted tentacula; c, ampulla 

 Dliana; d d d, intestinal canal; e, cloacal chamber opening externally by a wide orifice, into 



which the bristle,/, has been passed; g g, "respiratory tree;" hh, ovarium (testis in the male) ; 



ii, central vascular trunk; k, intestinal vessel; I, m, vessels in relation with the " resraratorv 



tree." 



the intestine, by a large opening leading to a wide membranous tube, 

 which immediately divides into two vessels (g g) forming the main 

 trunks of the beautiful arborescent branehia? ; these extend to the oppo- 

 site extremity of the body, giving off in their course numerous lateral 

 branches that divide and subdivide, so as to form what has been not 

 inaptly termed the " respiratory tree," until they ultimately terminate 



