Practice question

Enterocoelous formation of mesoderm and true coelom characterizes deuterostome development seen in Echinodermata Hemichordata and Chordata contrasting with schizocoelous mode in protostomes. During gastrulation archenteron wall evaginates as paired mesodermal pouches pinching off from endoderm expanding into blastocoel lumina coalescing to become eucoelom lined by mesoderm. Process termed enterocoely indicates gut origin of coelom. In echinoderms three pairs form axocoel hydrocoel somatocoel. Contrasts with schizocoelous where coelom forms by splitting mesodermal mass. Enterocoely produces trimeric organization in some deuterostomes emphasizing archenteric mesoderm source and deuterostome monophyly defined in embryology.