[Hydromedusae] The acellular substance lying between the ectoderm and the endoderm and forming the gelatinous bulk of the umbrella in the Hydromedusae (the jelly of jellyfish).

[Cubo-/Scyphomedusae] In Cnidaria, typically an acellular, gelatinous but firm layer between epidermis and gastrodermis. In polypoid forms usually functioning as an elaborate basement membrane and as a flexible skeleton; in medusoid forms the same in smaller organs such as tentacles and manubrium but across most of the bell, of which it forms the bulk, typically much thickened. In most medusae it is transparent and forms the jelly of jellyfish.

Alternative forms for Mesoglea : mesogleal, Mesogloea.