ORGANS OF DIGESTION. 331 



also attached. The oesophagus leads to a slightly enlarged 

 gastric portion (114. b. d.) of the intestine, which receives 

 the secretion of a large biliary follicle (114. c.) The 

 intestine is generally filled with sand and comminuted 

 shells, and the holothuria commonly lie among the ejecta- 

 menta of the sea where they appear to partake of a very 

 mixed and heterogeneous kind of food. The whole surface 

 of their body is traversed by longitudinal rows of long fleshy 

 tubular feet for progressive motion and to secure attachment ; 

 and on the lower surface, near the anterior extremity of the 

 trunk, is the common opening of all the divisions of the 

 ovary (114. k. k.} as in many of the entozoa and annelida. 

 The tentacula, like the tubular suckers along the body, 

 are protruded by the injection of a fluid into them from 

 their base. The long convoluted intestine (1 14. d. d.) passes 

 backwards along the whole extent of the abdomen, then 

 returns to near the mouth, and again turns backwards to ter- 

 minate in the middle of the cloaca (1 14,/.), connected along 

 this course, by a short delicate vascular mesentery (114. e. e.) 

 to the sides of the trunk. The two long ramified tubular 

 branchiae (1 14. h.) terminate in the cloaca by separate orifices 

 on each side of the rectal extremity of the intestine ; after 

 receiving the orifices of several small follicles (U 4. i). A 

 mucous, a muscular, and a peritoneal coat can be detected 

 on the delicate intestine of the holothuria, as in several other 

 echinoderma. The nutritious part of the food is taken 

 from the intestine by the mesenteric veins (114. /.) and 

 conveyed, with the venous blood of the system, to the long 

 ramified internal branchiae (114. h. h.), from which it is 

 again collected by the branchial veins (114. m.) to be dis- 

 tributed through the great systemic arteries without the 

 aid of a heart. As the cloaca (114,/.) is a capacious cavity 

 which inhales the water to be sent through the tubular 

 ramified gills (114. h. A.), the rectal portion of the intestine 

 (114. d.) is protruded through that cavity to the external 

 opening of the anus (114.^.) in evacuating its shelly con- 

 tents, as in the oviparous vertebrata. The whole digestive 

 apparatus of the holothurice are often forced out from the 

 body, through the mouth, by the contractions of the strong 

 muscular parietes of the abdomen, before death, and I have 

 found even the dental plates and their attached tentacula, 



