^M. cervicornis^, the stag-horn coral. This is a branching species which attains large size. Its manner of growth is as follows: At the tip of each branch is an individual polyp, which is larger than those which surround the branch. This is the original animal which started the branch, and is the parent from which all the others on the branch have budded. The large terminal polyp buds around the base; a surplus of lime also collects at the base and clogs its tissues, so that it no longer can perform the functions of life, and after a certain period the base becomes dead matter. The polyp on the upper end continues to live and rises above the excess of solid matter. At the same time it continues to form new buds. The buds become independent corallites and secrete an excess of calcareous matter at their bases, which cements them to the parent stock and increases the thickness of the branch. Thus, as the original polyp constantly rises and buds, the colony assumes a stem-like form, covered with numerous individuals. Certain polyps on the main stem have the attributes of the parent animal. These start branches, and so the process goes on, and in time the colony becomes much branched and arborescent in form. In the living coral each little polyp is like a minute sea-anemone, having a colored cylindrical body surrounded on its upper disk with numerous tentacles. (Plate XLV.) [pg150] ^M. palmata.^ This madrepore grows like the one described above, except that the branches do not remain separated, but unite or grow together, giving broad, flat surfaces which resemble fronds. When carefully examined these surfaces show striations which indicate the course of the branches. The structures forming the lobes are caused by the failure of the branches to unite. On the Carysfort Reef of the Florida Keys this species covers the top of the reef for several miles, nearly reaching the surface, and appears like a vast bed of low yellow shrubbery. (Plate XLV.) GENUS ^Astrangia^ ^A. danaë.^ A small coral found on the New England coast. It lives in the clefts of rocks in small patches, sometimes two to three inches across and one quarter of an inch or more high. Frequently it is like a thin crust of lime covered with star-like divisions. Sometimes it forms branches. The living animals are white, and when expanded rise above the cells and resemble a cluster of small sea-anemones. SUBCLASS =ALCYONARIA= or =HALCYONOIDA= [Illustration: /Alcyonium palmatum/: /A/, entire colony; /B/, spicules.]