Development. Coelom is the mesodermally lined cavity between the gut and the outer body wall. During the development of the embryo, coelom formation begins in the gastrulation stage. The developing digestive tube of an embryo forms as a blind pouch called the archenteron.

When did the coelom arise?

It contains most of the visceral organs. Coelom arises as a secondary body cavity between two embryonic layers of mesoderm. The term coelom was suggested by Haeckel in 1872.

Where did coelom develop?

The coelom develops within the mesoderm during embryogenesis. Of the major bilaterian phyla, the molluscs, annelids, and arthropods are schizocoels, in which the mesoderm splits to form the body cavity, while the echinoderms and chordates are enterocoels, in which the mesoderm forms as two or more buds off of the gut.