[Hydromedusae] During the development of a medusa bud, an opening provides continuity and exchanges between the "mother" gastric cavity and that of the bud. Generally this aperture disappears after liberation, but in some medusae it remains as a small canal or duct projecting from the manubrium into the apical mesoglea, often leading upwards to the outside (e.g., Sarsia producta, Corymorpha nutans).

Alternative form for Apical canal : Umbilical canal.