268 



SUBKItfGDOM CCELENTEEATA. 



Fig. 



The Sea-fan is another representative form of sclerobasio 



coral, the branches having a horny axis (as may be detected 



by the smell in burning), and uniting in a beautiful net- work. 



The Madrepores and other reef-forming corals deposit 



within the tissues of the animal a calcareous frame- work of 



sclerodermic coral. 



The Mushroom Coral is 

 remarkable as being the 

 skeleton of a single Polyp, 

 often fifteen inches in diam- 

 eter. Though fixed in its 

 early stages, it becomes free, 

 and, but for its habit of lying in the clefts of the rocks, 

 would be speedily destroyed by the violence of the waves. 



The Organ-pipe Coral consists of cylindrical tubes arranged 

 like the pipes in a church organ. Each one is the cell of 

 a single polyp, and the whole number in the mass is the 

 progeny of the one that first became fixed at the base. 



Fig. U58. 



Ctenactis echinata, Mushroom Coral. 



'I'utnpora musica, Organ-pipe Coral. 



* Dana, in describing the coral reefs of the Pacific, says The actiniae (Fig. 459) 

 may well be called the asters, carnations and anemones of the submarine garden ; 

 the tubipores (Fig. 458) are literally its pink beds ; the gorgoniae (Fig. 456) its flow, 

 ering twigs ; the madrepores (Fig. 455) its plants and shrubbery. Astrseas (star 

 corals) often form domes amid the grove, a dozen feet or more in diameter, em- 

 bellished with green or purple blossoms, which stud the surface like gems ; hemi- 

 spheres of meandrina (brain coral) appear as if enveloped in a network of flowering 

 Vines ; and vases of madrepores stand on a cylindrical base covered with branches 

 spreading gracefully from the center and decked with sprigs of tinted polyps. 



