XV.] CORAL LAND. 249 



a true insect is divided into segments ; it has a digestive canal 

 which does not open into the cavity of the body ; it has 

 distinct organs of circulation and respiration, and a peculiarly 

 formed nervous system. None of these features are to be 

 met with in the sea-anemone ; which, therefore, is an animal 

 of much lower grade than an insect. Indeed, it is much 

 more nearly allied to the jelly-fishes, which float in the sea, 

 and to the fresh-water polypes of our ponds. The general 

 name of "polype"^ is, in fact, applied to the sea-anemones 

 no less than to the latter. 



The substance of the body of the common sea- 

 anemones is quite soft, and none of them acquire a greater 

 consistency than that of a piece of leather. But there are a 

 few animals, which live at considerable depths in our own 

 seas, and very many in other parts of the ocean, the 

 structure of which is, in all essential respects, similar to 

 that of the sea-anemones, but which nevertheless possess a 

 very hard skeleton (Fig. 70). This skeleton, inasmuch as 

 it is forined by the solidification of the base and side walls 

 of the body of the polype, necessarily has the form of a cup, 

 and it is termed a cup coral, to distinguish it from other 

 kinds of coral such as the red coral, which, though produced 

 by similar animals, are formed in a different manner. Not 

 only are the walls of the body thus hardened, but vertical 

 partitions of the same character extend from the walls of 

 the cup to its centre, in correspondence with the partitions 

 which divide the cavity between the inner sac and the body- 

 wall. The hardening of the lower part of the body of the 

 coral polype, and that of the partitions, is effected by the 

 deposition, within their substance, of carbonate of lime 



' Polype, from TToXi)?, /s/K.r, '•many," and iroi'i, pous, "foot;" an 

 an'mal with several feet or several tentacles ; thus the octopus derives 

 its name from having eight of these organs. 



