The comparison of the metagenetic type of development, such as that of Aurelia, with the more primitive genera of Scyphomedusae, indicates clearly that the scyphistoma and ephyra are recapitulative larval stages which are represented by the adult forms of primitive genera, making such allowances as are necessary when comparing adult and larval forms. The metagenesis has arisen through the scyphistoma-larva acquiring the power of larval proliferation by budding.
A similar origin for metagenesis has been discussed under the Hydromedusae (q.v.).
In Trachylinae also the beginnings of a similar metagenesis can be found.
It will be seen elsewhere, however, that whatever view may be held as to the origin of metagenesis in Hydromedusae, in the case of Scyphomedusae (q.v.) no other view is possible than that the alternation of generations is the direct result of larval proliferation.