Usually the four subgenital cavities are distinct from each other (so-called tetrademnic condition), but in many Rhizostomeae, for example, Crambessa, the subgenital cavities join together under the subumbral floor of the stomach (so-called monodemnic condition) and coalesce to form a so-called subgenital portico placed on the oral side of the stomach, opening by four interradial apertures between the oral arms, that is to say, by the four primitive apertures of the subgenital pits.
Interradial tentacles may be also developed, so that the total number present may be increased to eight or to an indefinitely large number.
The four sub-genital pits are seen to be interradial.
The eight adradial gonads on the subumbral walls of the four radial pouches, representing primitively four horse-shoeshaped gonads each divided into two by an interradial septum.
The four gastric interradial ridges are seen through the mouth.