NUTRITION IN THE ASTERIAS. 77 



stomach; and the stomach continued into a regular intestine, 

 which takes two turns in the cavity of the body, before it 

 terminates. 



The alimentary tube in the lower animals frequently ex- 

 hibits dilatations in different parts: these, if situated in the 

 beginning of the canal, may be considered as a succession 

 of stomachs; while those that occur in the advanced por- 

 tions are more properly denominated the great intestine, 

 by way of distinction from the middle portions of the tube, 

 which are generally narrower, and are termed the small in- 

 testine. We often see blind pouches, or caeca, projecting 

 from different parts of the canal; this is the case with the 

 intestine of the JJphrodita aculeata, or sea-mouse. The in- 

 testine being generally longer than the body, is obliged to 

 be folded many times within the cavity it occupies, and to 

 take a winding course. In some cases, on the other hand, 

 the alimentary tube passes in nearly a straight line through 

 the body, with scarcely any variation in its diameter; this 



is the case with the Jlscaris, which 



250 ^^^^: 



^e^^^v/ j s a l on g cylindric worm; and 



nearly so with the Lumbricus 

 terrestris, or earth-worm. In the 

 Nais, on the contrary, as shown 

 in Fig. 259, the alimentary tube 

 presents a series of dilatations, 

 which, from the transparency of the skin, may be easily seen 

 in the living animal. The food taken in by these worms 

 is observed to be transferred from the one to the other of its 

 numerous stomachs, backwards and forwards many times, 

 before its digestion is accomplished. 



The stomach of the Leech is very peculiar in its struc- 

 ture: its form, when, dissected off, and removed from the 

 body, is shown in Fig. 260. It is of great capacity, occu- 

 pying the larger part of the interior of the body; and its ca- 

 vity is expanded by folds of its internal membrane into se- 

 veral pouches (c, c, c.) Mr. Newport, who has lately 



