Biology of Animals, Sixth Edition . Some, however, have no medusa stage, and some occur only as medusae and have no polyp stage. A few, such as Cyanea , may attain a bell diameter exceeding 2 m and tentacles 60 to 70 m long, but most range from 2 cm to 40 cm in diameter. Their polyp stage is absent or greatly reduced, and the medusae of this class have no velum . They do not have a medusa stage .
Anthozoans are all marine and are found all over the world, in various sizes and habitats.
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