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 ^M 

 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 

 Edwardsia. 



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- camja J 'produced. 

 mesenterial chambers. 



Order 1. Zoantharia. We will now enumerate some of 

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

 tharia, 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 Dcltocyathus and Caryo- 

 pliyllia, the coral forms a cup or theca, the lamellae which 

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

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

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



