474 HOLOTHTTRIA; SIPUNCULUS. 



ary tube, of nearly uniform diameter throughout ; which, after 

 many convolutions, terminates at or near the opposite extremity 

 of the body. The Holothuria has the power of drawing inwards 

 its tentacula, and of closing its mouth around them ; so that no 

 appearance of them can be seen. It is probably by a movement 

 of this kind that it swallows its food, which seems to consist of 

 almost any kind of organised matter that falls in the way o ' the 

 animal ; for the intestine is generally found distended with sand, 

 in which may be detected the remains of corals, sea-weeds, and 

 other marine substances. In the Holothuria the sucking feet 

 are distributed irregularly over the surface of the body ; but in 

 the Pentacta (Fig. 710) they are arranged in five longitudinal 

 rows. In the Psolus, again, they are confined to a flat disc, 

 which thus forms a foot analogous to that of the Gasteropod 

 Mollusks, which these animals somewhat resemble in form ; and 

 in Synapta they are entirely wanting. There are some interest- 

 ing points in the internal organisation of this group, which tend to 

 show its relationship to the Articulata; and their analogy to 

 that group is further shown in their power of comparatively 

 active locomotion. By the flexibility of their integument, and 

 the muscular fibres with which it is furnished, they are able to 

 swim and crawl with facility. Some of them frequent deep 

 waters ; whilst others are found among rocks and floating sea- 

 weeds, at no great distance from the shore. 



1114. Near the Holothuria we are probably to place the 

 Sipunculus and its allies; although the worm-like aspect of 



their bodies, and the entire ab- 

 sence of either prickles or tubular 

 feet from the skin, would lead us 

 to suppose them entirely different 



PIG. 711-8IFUXCDWS. in Character. In fact they consti- 



tute an extremely aberrant group 



just such as' the philosophic Naturalist might expect to find 

 between classes formed upon types so different as the Radiated 

 and Articulated. The mouth is not surrounded by radiating 

 arms, as in the Holothurice^ but it is armed, in many species, 

 with a set of teeth arranged in a pentagonal form, like those of 



