3. (Bryozoa) a. In Gymnolaemata, water-filled space partly enclosed by the body wall of one or more polymorphs, in which embryos grow during development. See also ovicell. b. In Stenolaemata, a zooidal or extrazooidal internal coelomic chamber that encloses eggs developing into larvae.
5. (Mollusca: Gastropoda) In female Argonauta, a beautiful, calcareous, bivalve case secreted by the two dorsal arms into which the eggs are deposited; females retain and usually remain with the posterior of her body in the case; when disturbed, she withdraws completely into the retreat.