CORAL POLYPS. 



79 



lives in deeper water. Its young, however, is at an early 



stage of its existence a free-swimming polyp, which was 



originally described as an adult animal under the name of 



Arachnactis. In Zoanthus the tegument is tough and 



leathery, and the different polyps are con- 



nected by stolons. Epizoanthus americanus 



Verrill lives in deep water, off the coast of 



New Jersey and Southern New England, in 



about twenty fathoms. Cerianthus, a gigantic 



form, a native species of which (C. borealis 



Verrill) lives at the depth of one hundred 



fathoms in the Gulf of Maine deeply sunken 



in the mud, where it secretes a shiny leathery 



tube, is perforated at the end of the body ; 



the young of a corresponding European 



species is also free-swimming, like the young 



Edwurdsia. 



The coral polyps differ from the Actinoids 

 in secreting in the mesoderm a limestone 

 base, from which arise in the Zoantharian 

 corals stony septa serving as a support to the 

 animal ; these septa are deposited or secreted 

 in the chambers, so that in the coral polyp 

 there are soft partitions alternating with the 

 limestone ones, the latter formed at the base 

 of the polyp, not completely filling the inter- ocmja 

 mesenterial chambers. 



Order 1. Zoanthana. "We will now enumerate some of 

 the leading forms of the first order of Anthozoa, the Zoan- 

 tliaria, to which the sea-anemones and most of the stony 

 corals belong. The group is called by some recent authors 

 Hexacoralla, the number of primary chambers and tenta- 

 cles being six, the latter rounded, conical, or filiform. In 

 the simple cup-shaped corals, as DcUocyathus and Caryo- 

 pliyllia, the coral forms a cup or theca, the lamella? which 

 arise from the base terminate in as many septa, the spaces 

 between which are termed loculi. A central pillar or col- 

 umn formed by the union of the septa, or arising indepen- 



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