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. pizoanthus 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 
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- omnes ele 
mesenterial chambers. oe 
Order 1. Zoantharva.—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 
Hezxacoraila, the number of primary chambers and tenta- 
cles being six, the latter rounded, conical, or filiform. In 
the simple cup-shaped corals, as Deltocyathus and Caryo- 
phyllia, the coral forms a cup or ¢heca, the lamelle which 
arise from the base terminate in as many septa, the spaces 
between which are termed Joculi. A central pillar or col- 
umn formed by the union of the septa, or arising indepen- 
