Noun
any of the numerous minute canals lined with choanocytes which radiate from the paragastric cavity in some sponges and end just below the surface of the sponge
any of the canals extending through the substance of the umbrella from the gastric cavity to the marginal circular canal in jellyfish
a tube extending outward along each ambulacral area from the circumoral canal in most echinoderms
Source: en.wiktionary.org