ALCTONARIAN POLYPS. 85 



many forms of tabula?, are certainly characters not opposed 

 to the alliance of these corals with the Alcyonarians," and 

 gives other reasons of importance in favor of this view. 



The group of Antipathea, represented by Antipathes ar- 

 borea Dana, of the Feejee Islands, produce compound 

 groups by budding, growing in the form of delicate shrubs. 

 The polyps have usually six tentacles, though in Gerardia 

 they have twenty-four. 



Order 2. Alcyonaria. To this group of polyps, which 

 have eight serrated or feathered tentacles, belong the red 

 coral of commerce, the sea-fans and sea-pens, in which there 

 are no calcareous septa, and in which the corallum has, as in 

 the sea-fans and sea-pens, a bony axis, while the flesh}' por- 

 tion (coenosarc) represents the mesoderm and is filled with 

 calcareous spicules. 



In the genera Haimea, Alcyonium, Tubipora, etc., the 

 polyps are encrusting, budding out in different ways, and 

 adhere to foreign bodies by the coenenchyma. ffaimea is 

 simple, consisting of but a single polyp. In Alcyonium 

 the coenenchym is much developed, soft, lobulated, and 

 branching. Our common species is A. car mum Agassiz. 

 In Tubipora the polyps are compound and secrete solid 

 calcareous, bright red tubes, arranged side by side, like the 

 pipes of an organ, and supported by horizontal plates. 



In ' the common red coral (Corallium rubrum) of the 

 Mediterranean Sea, the solid, unjointed coral-stock consists 

 of a crystalline basal mass, with calcareous spicules solidly 

 united. The bright red coral is worked into various orna- 

 ments. The coral fishery is pursued on the coasts of Algiers 

 and Tunis, where assemble in the winter ai.d spring from 

 two hundred to three hundred vessels. The coral-fishermen, 

 with large rude nets, break off the coral from the submerged 

 rocks. About half a million dollars' worth of coral is annu- 

 ally gathered. 



Heliopora, now proved by Mr. H. N. Moseley to be an 

 Alcyonarian instead of an Actinoid polyp, differs from 

 Corallium and Tubipora "in that the hard tissue of its 

 corallum shows no signs of being composed of fused spic- 

 ules." This genus, together with Polytremacis and the 



