We shall describe three genera, the two first of which belong to the Madreporæa, and the last of the family of the Porides.
Fig. 74. Dendrophyllia ramea, half natural size (De Blainville).
Dendrophyllia ramea, represented in Figs. 75 and 76, is an elegant madrepore of the Mediterranean. Its polyp presents a very large trunk charged with short ascending branches; it usually attains to about a yard and a half in height. The polyps are provided with a great number of tentacula, in the centre of which the mouth is placed. They are deeply buried in the cells, which radiate from numerous unequally saillant plates. Peyssonnel, who had seen the polyps of this colony, says: "I may observe that the extremities or summits of the branching madrepore, the species in question, which in the Provencal we call Sea-fennel, is soft and tender, filled with a glutinous and transparent mucous thread, similar to that which the snail leaves on its path. These extremities are of a fine yellow colour, five or six lines in diameter; soft, and more than a finger's breadth in length. I have seen the animal nestling in them; it seemed to be a species of cuttle-fish or sea-nettle. The body of this sea-nettle must have filled the centre; the head being in the middle, surrounded by many feet or claws, like those of the cuttle-fish. The flesh of this animal is very delicate, and is easily reduced to the form of a paste, melting almost under the touch."
Fig. 75. Dendrophyllia rameaFig. 76. A part magnified.
(De Blainville).
Natural size, with polypi.
The madrepores abound in all intertropical seas, taking a considerable part in the constitution of the reefs which form the coral and madreporic islands so conspicuous in the ocean. The tree-like Dendrophyllia (D. ramea, Figs. 75 and 76) have cells of considerable depth, radiating into numerous lamellæ, forming a widely-branching arborescent coral, externally striated, internally furrowed, and truncate at the extremities. The animals are actiniform, furnished with numerous cleft tentacula, in the centre of which is the polygonal mouth. In the Lobophyllia, the tentacula are cylindrical, the cells conical, sometimes elongated and sinuous, with a sub-circular opening terminating the few branches of the polyp, which is fixed, turbinate, and striated. The Plantain Madrepore, M. plantaginea (Lamarck), is an interesting example, the polyp presenting itself, as in Fig. 77, in tufts, with slender and prolific branches.