NUTRITION IN THE ACTINIA. 



99 



step higher in the scale, we find that the stomach 

 and intestinal tube, together with their appen- 

 dages, are distinct organs, formed by membranes 

 and coats proper to each, and that they are 

 themselves contained in an outer cavity, which 

 surrounds them, and which receives and collects 

 the nutritious juices after their elaboration in 

 these organs. The Actinia, or Sea Anemone, for 

 example, resembles a polypus in its general 

 form, having a mouth, which is surrounded with 

 tentacula, and which leads into a capacious 

 stomach, or sac, open below, and occupying 



the greater part of the 

 bulk of the animal ; but 

 while, in the polypus, 

 the sides of the stomach 

 constitute also those of 

 the body, the whole 

 being one simple sac ; in 

 the actinia, spaces inter- 

 vene between the coats 

 of the stomach, and the skin of the animal. As 

 the stomach is not a closed sac, but is open below, 

 these cavities are, in fact, continuous with that 

 of the stomach : they are divided by numerous 

 membranous partitions passing vertically between 

 the skin, and the membrane of the stomach, and 

 giving support to that organ. Fig. 257, repre- 

 senting a vertical section of the Actinia coriacea, 

 displays this internal structure, b is the base 



