638 
RADIATA. 
tially divided by imperfect transverse partitions. Most of tlie zoopliytes 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, vs'inding depressions in the surface of the coral. 
THE FUNGID^. 
In the Fungidce the polypes are single and often attain a considerable size. The polypidoms 
form oblong 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 wdth a tubular mouth in the centre, 
and with numei'ous short, round tentacles, which are scattered over the upper surface. 
THE ZOANTHIDiE. 
The family Zoantkidce consists of somewhat clavate polypes, presenting a considerable resem- 
blance in their general structure to the Actinim. They difi'er 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 
a? it runs along. The mouth is surrounded by a single row of tentacles. 
ACTINIA OE SEA-ANKMONE. THE MOCTH OP THE SEA-ANEMONE. 
THE ACTINIAD^. 
We now come to the Sea-Anemones^ or Sea- Carnations, of which there are several species on 
T)ur own coasts; but it is in the seas of tropical latitudes that they are to be found in the greatest pro- 
fusion, and presentiug 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 atoUs or lagoon-reefs, 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 live 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 ver}^ waves which appear to 
threaten the island with destruction. The violence of the storm breaks ofi" 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 maybe obtained from the following remarks by Mr. Dana : 
" Calculating the number of piolypes that are xmited 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 
