Origin of metagenesisModL: see meta- and -genesis
The definition of metagenesis is the reproduction cycle of an organism that alternates between sexual and asexual generations.
An example of metagenesis is the reproduction cycle of a cnidarian.
Biol. reproduction in which there is alternation of an asexual with a sexual generation, as in many cnidarians
Alternation of generations between sexual and asexual forms.
meta- +"Ž -genesis
- In Trachylinae also the beginnings of a similar metagenesis can be found.
- They typically present two structural forms, the non-sexual hydroid and the sexual medusoid; in such a case there is an alternation of generations (metagenesis), the hydroid giving rise to the medusoid by a sexual gemmation, the medusoid bearing sexual cells which develop into a hydroid.
- The development from the egg may be direct, or may take place with an alternation of generations (metagenesis), in which a non-sexual individual, the so-called scyphistoma or scyphopolyp, produces by budding the sexual medusae.
- 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.).