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Cnidarian Body Plan: Polyp and Medusa

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State

A cnidarian body takes one of two forms: a stationary, tubular polyp, or a free-swimming, bell-shaped medusa; some species alternate between both.

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A sea anemone lives only as a polyp; a jellyfish spends most of its life as a medusa, though some pass through a polyp stage too.

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Polyp and medusa name life-cycle stages within one species, not two separate cnidarian groups.