Schizocoely (adjective forms: schizocoelous or schizocoelic) is a process by which some animal embryos develop. Animals which develop through schizocoely are known as schizocoelomates. Schizocoely occurs when a coelom (body cavity) is formed by splitting the mesodermal embryonic tissue.
Schizocoelous development is typically attributed to protostomes: phyla Mollusca, Annelida, and Arthropoda, but some deuterostomes can exhibit schizocoely as well.
The term refers to the order of organization of cells in the gastrula leading to development of the coelom. In these three phyla of organisms, the mesoderm (the middle germ layer) forms as a solid mass of migrated cells from the single layer of the gastrula. The new mesoderm then splits, creating the pocket-like cavity of the coelom.