638 



RADIATA. 



tially clividcil by imperfect transverse partitions. Most of the zoophytes of this family appear to 

 increase by a sort of spontaneous division, instead of gemmation. By this means the body of the 

 polype, and the cavity it occupies, are in many cases not distinctly circumscribed; and the latter 

 form curious, elongated, winding depressions in the surface of the coral. 



THE FUNGID^. 



In the Fiuifjidce the polypes arc single and often attain a considerable size. The polypidoms 

 form oblono- or roundish masses, furnished with an extraordinary number of rays, the outermost 

 of which project from the circumference without being confined by any outer walls. The polype 

 occupies the whole of this radiated edifice ; it is furnished with a tubular mouth in the centre, 

 and with numerous short, round tentacles, which are scattered over the upper surface. 



THE ZOANTHID^. 



The family Zoanthhice consists of somewhat clavate polypes, presenting a considerable resem- 

 blance in their general structure to the Actinice. They ditfer from these, however, in being social 

 in their mode of life, a number of polypes being united by a common creeping stem, which 

 attaches them to some submarine object, and from which new polypes are produced at intervals 

 as it runs along. The mouth is surrounded by a single row of tentacles. 



i y\\ ij 



ACTINIA OR SEA-AKEMONE. 



THE MOUTH OF THE SEA-ANEMONE. 



THE ACTINIAD^. 



We now come to the Sea-Anemones^ or Sea-Caimations, of which there are several species on 

 "Dur own coasts; but it is in the seas of tropical latitudes that they are to be found in the greatest pro- 

 fusion, and presenting the most beautiful appearance. Their tentacles, which are disposed in regular 



crescent-like form, even sometimes completely circular, inclosing, as within a wall, a basin of still water, called a lagoon, 

 in which the more delicate marine animals find a welcome refuge from the tumultuous waves which rage without. 

 These islands, which are called aMls or lagoon-reffs, are generally highest on the windward, or eastern side, against 

 which the waves are continually dashing with great violence ; the polypes, from some cause still unexplained, building 

 with greater rapidity on that portion of the reef which is constantly exposed to the action of the breakers. On the 

 opposite or leeward side, the reef is seldom completed ; so that at this part the lagoon usually communicates with 

 the open sea by an opening of variable width. As exposure to the air appears quickly to be fatal to these polypes, 

 they never raise their habitations quite to the surface of the water, usually stopping at four or five feet below low- 

 water mark. It is evident, therefore, that the living polypes can have nothing to do with the final elevation of the 

 coral islands above the level of the sea; and we find that this is due to the action of the very waves which appear to 

 threaten the island with destruction. The violence of the storm breaks off large fragments from the lower parts of 

 the reef, and washes them up to its surface, where they rest, and gradually become agglutinated together by a con- 

 stant deposit of calcareous sand, produced by the disintegration of the coral. In course of time these deposits rise 

 above the surface. 



Few things in nature can give us a more vivid conception of the power of that Omnipotent Creator at whose com- 

 mand these apparently insignificant creatures rear their stupendous edifices from the deep. Some idea of the 

 number of architects required to produce these vast results may be obtained from the following remarks by Mr. Dana : 

 " Calculating the number of polypes that are united in a single Astrsea dome twelve feet in diameter, each covering 

 a square half inch, we find it exceeding one hundred thousand ; and in Porites of the same dimensions, in which the 



