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One of a peculiar kind of cups, or calicles, found upon hydroids of the family Plumularidæ. They contain nematocysts. See Plumularia.

(Biol.) See Idioplasma. -- Nutritive polyp (Zoöl.), any one of the zooids of a compound hydroid, or coral, which has a mouth and digestive cavity. -- Nu"tri*tive*ly, adv. -- Nu"tri*tive*ness, n.

A minute soft filamentary process springing from the surface of certain hydroids and sponges.

The hard outer covering of hydroids and other marine animals; the perisarc.

A sac which surrounds the generative bodies in the gonophore of a hydroid.

The outer, hardened integument which covers most hydroids.

A branch of a plumularian hydroid specially modified in structure for the protection of the gonothecæ.

Any free-swimming gonophore of a hydroid; a hydroid medusa.

Any hydroid belonging to Plumularia and other genera of the family Plumularidæ. They generally grow in plumelike forms.

One of the feeding or nutritive zooids of a hydroid or coral.

A coloring matter found in many simple Anthozoa and some hydroids.

A coral, or corallum; also, one of the coral-like structure made by bryozoans and hydroids.

One of the feeding zooids, or polyps, of a coral, hydroid, or siphonophore; a hydranth. See Illust. of Campanularian.

Producing sexual zooids by budding; -- said of the blastostyle of a hydroid.

A small branch, or branchlet, of corals, hydroids, and similar organisms.

The young attached larva of Discophora in the stage when it resembles a hydroid, or actinian.

A sertularian hydroid, especially Sertularia abietina, which branches like a miniature fir tree.

A hydroid coral of the genus Millepora, especially M. alcicornis, of the West Indies and Florida. So called because it stings the tongue like ginger. See Illust. under Millepore.

A genus of delicate branching hydroids having small sessile hydrothecæ along the sides of the branches.

Any species of Sertularia, or of Sertularidæ, a family of hydroids having branched chitinous stems and simple sessile hydrothecæ. Also used adjectively.