Stomochord
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The stomochord is an flexible, hollow tube found in hemichordates. Stomochords were initially considered primitive notochords, but are now recognized to not share histological composition to that of the notochord found in chordates.[citation needed]
Stomochords arise 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. Their walls are composed primarily of epithelial cells, but ciliated and glandular cells are also present. [citation needed]