The reproductive organs producing the sexual product; the term gonads is used for hermaphroditic organs. When only eggs are produced (females) they are ovaries, when only sperm is produced they are testis.

[Hydromedusae] There are no real reproductive organs in Hydrozoa, so this term is inappropriate although widely used. In medusae it indicates the place where the sex cells become mature; this may happen on the manubrium walls and/or at the level of the radial canals. The position of the germ cells has considerable value as a diagnostic character. When the "gonads" are on the manubrium they may completely surround it, being cylindrical, or occupy an interradial, adradial, or perradial position. When located on the radial canal, they usually develop on the lateral walls of the canals, but in some medusae they are continuous also over the ventral wall (e.g., Clytia hemisphaerica). Their position along the course of the radial canals, shape and size are often a diagnostic character.