| 21. | After fertilisation, each embryo develops within a day or so into a free-swimming planula larva.
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| 22. | The released eggs are fertilized, and the resulting zygote develops quickly into a multicellular " planula ".
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| 23. | After 3 days the egg develops in a planula; at this stage movement is only done by ciliary action.
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| 24. | The free-swimming planula larvae eventually settle on the seabed and develop into juvenile polyps which found new colonies.
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| 25. | The fertilised egg develops into a planula, which settles after fifteen to twenty days and grows into a new individual.
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| 26. | The fertilized egg develops into a planula larva which drifts with the plankton before settling and developing directly into another polyp.
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| 27. | The egg hatches into a free-swimming planula larva that settles on the seabed when it has completed its development.
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| 28. | Reproduction involves the release of planula larvae which spend somewhere between a few hours and several days in the open sea.
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| 29. | Planula larvae that develop from fertilised eggs sink to the seabed five days later and undergo metamorphosis to found new colonies.
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| 30. | As a planula settles down, it gives rise to a colony of polyps that are attached to the sea-floor.
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