76 



THE VITAL FUNCTIONS. 



of a mouth, leading to s, the stomach, of which the lower 

 orifice is open, and which is suspended in the general cavi- 

 ty, by means of vertical partitions, of which the cut edges 

 are seen below, uniting at a central point, c, and passing be- 

 tween the stomach and the integument. These muscular 

 partitions are connected above with three rows of tentacula, 

 of which the points are seen at T. The ovaries (o) are seen 

 attached to the partition; and also the apertures in the lower 

 part of the stomach, by which they communicate with its 

 cavity. 



If we considered the medusa as having four stomachs, we 

 might in like manner regard the Jlsterias, or star-fish, as 

 having ten, or even a greater jaurnber. The mouth of this 



258 



radiated animal is at the centre of the under surface; it leads 

 into a capacious bag, situated immediately above it, and 

 which is properly the stomach. From this central sac there 

 proceed ten prolongations, or canals, which occupy in pairs 

 the centre of each ray, or division of the body, and subdi- 

 vide into numerous minute ramifications. These canals, 

 with their branches, are exhibited at c, c, Fig. 258, which 

 represents one of the rays of the Asterias, laid open from 

 the upper side. The canals are supported in their positions 

 by membranes, connecting them with the sides of the ca- 

 vity in which they are suspended. 



In the various species of Echini, we find that the ali- 

 mentary tube has attained a more perfect development; for 

 instead of constituting merely a blind pouch, it passes en- 

 tirely through the body of the animal. We here find an 

 oesophagus, or narrow tube, leading from the mouth to the 



