01 n. 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 ri…
pl.
Planulæ ((#))
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1.
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.(Biol.) Also: gastrula
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2.
The very young, free-swimming larva of the cœlenterates. It usually has a flattened oval or oblong form, and is entirely covered with cilia.(Zool.)