• WordNet 3.6
    • n planula the flat ciliated free-swimming larva of hydrozoan coelenterates
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Webster's Revised Unabridged Dictionary
    • Planula (Biol) In embryonic development, a vesicle filled with fluid, formed from the morula by the divergence of its cells in such a manner as to give rise to a central space, around which the cells arrange themselves as an envelope; an embryonic form intermediate between the morula and gastrula. Sometimes used as synonymous with gastrula.
    • Planula (Zoöl) The very young, free-swimming larva of the cœlenterates. It usually has a flattened oval or oblong form, and is entirely covered with cilia.
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Century Dictionary and Cyclopedia
    • n planula The ordinary locomotory embryo of the cœlenterates, which is of flattened form, mouthless, ciliate, and free-swimming. The term originally applied only to such embryos of certain hydrozoans, but has become more comprehensive. See cut under blastocœle.
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Chambers's Twentieth Century Dictionary
    • n Planula plan′ū-la the locomotory embryo of the cœlenterates
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Webster's Revised Unabridged Dictionary
L., a little plane


In literature:

The larvae of corals are free swimming ciliated forms known as planulae, and they do not acquire a corallum until they fix themselves.
"Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 2" by Various
Hence the principal axis of the future medusa corresponds, not to the longitudinal axis of the planula, but to a transverse axis.
"Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 2" by Various