Definitions for "Planula"
The very young, free-swimming larva of the cœlenterates. It usually has a flattened oval or oblong form, and is entirely covered with cilia.
offspring of medusae, the second free-swimming stage of a polyp's life cycle
The planktonic larval form produced by scleractinian corals and coelenterates.
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.