part of part of in taxon develops from develops from existence starts during Hemichordata Eumetazoa embryo stage multi-tissue structure presumptive gut stomochord Wikipedia:Stomochord stomatochord A flexible, unpaired, hollow tube found in hemichordates that arises in embryonic development as an outpocketing from the roof of the embryonic gut anterior to the pharynx. In adults, they extend dorsally from the pharynx into the probiscis, and serve to communicate with the oral cavity. UBERON:0011288 Their walls are composed primarily of epithelial cells, but ciliated and glandular cells are also present.