strobiliation

In the life cycle of Scyphozoans, the medusa is the form that predominates. Nevertheless, scyphozoan life cycles also typically include a polyp form called a scyphistoma. The scyphistoma feeds with a ring of tentacles around the mouth. It undergoes asexual reproduction via transverse fission, and short stacks of genetically identical organisms, which will eventually bud off to become physiologically, anatomically separate individuals, are formed at the oral end of the polyp. The tranversly fissioning polyp is called a strobila. The individuals that bud off to swim freely in the water column are ephyrae, which are baby jellyfish. It is the adult jellyfish that makes gametes and reproduces sexually. A nice series of photos illustrating the life cycle of Aurelia labiata can be seen here. The scyphistoma typically exhibits strobilation only during a certain season. At other times it feeds as any solitary polyp would.