| Fertilized eggs may be brooded for a time or may develop directly into a free-swimming, ciliated planula larva. |
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| The planula larva settles on a hermit crab shell and metamorphoses into a primary polyp. |
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| This complicated bilayered structure is typical of anthozoan late planula larvae. |
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| Schematic view of a transverse section of the late planula of the anthozoan Euphyllia rugosa. |
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| Hydra lives in freshwater, lacks a ciliated planula, and has clearly lost a medusa stage during its ancestry. |
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| Fertilized eggs develop into crawling planula larvae which settle on hermit crab-occupied shells, and subsequently metamorphose into primary polyps. |
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| A young planula settles down as a sedentary polyp, which can sprout more polyps, sometimes for several years. |
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| A few omit the planula, polyp and ephyra phases and produce new medusae directly from eggs. |
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| In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae. |
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