coralArticle Free Pass coral, any of a variety of invertebrate
marine organisms of the class Anthozoa (phylum Cnidaria) that
are characterized by skeletons—external or internal—of a
stonelike, horny, or leathery consistency. The term coral is
also applied to the skeletons of these animals, particularly to
those of the stonelike corals. Stony corals (order Madreporaria
or Scleractinia) number about 1,000 species; black corals and
thorny corals (Antipatharia), about 100 species; horny corals,
or gorgonians (Gorgonacea), about 1,200 species; and blue corals
(Coenothecalia), one living species. The body of a coral animal
consists of a polyp—a hollow, cylindrical structure attached at
its lower end to some surface. At the free end is a mouth
surrounded by tentacles. The tentacles, which gather food, are
more or less extensible and are armed with specialized stinging
structures, called nematocysts, that paralyze prey. Eggs and
sperm, usually produced by separate individuals, develop as
outgrowths in the gastrovascu