Metamorphosis of a scyphomedusa (Pelagia panopyra)

Along the coasts from the middle part of Honshu southwards to Formosa, the pink-coloured scyphomedusa is often found in the " Kuroshiwo Stream," especially in spring. The medusa has no sessile stage throughout life : the planula developed from an egg undergoes a metamorphosis directly into an ephyra. In my collection several young stages of the species are found, including planulae and ephyrae. The process of the development from the planula to an ephyra being described in detail by A. Goette (1893)1) for Pelagia noctiluca, only the metamorphosis from the ephyra to the adult will be here reported. The youngest ephyra just developed from a planula is about 2 mm in diameter and easily distinguished from ephyrae of other Scypho medusae, such as Aurelia and Mastigias, by its pointed ephyral lappets, narrow sensory radial canals and conspicuous nematocyst clusters which are sparsely distributed on the whole sur face (Fig. 1). Besides eight radial canals, each leading to a sensory organ, there are eight adradial diverticula, each with a round head and extending from the spacious central stomach cavity to the margin. Gastral filaments, one in each interradius. Subgenital porticus faintly developed. Ring muscle weakly developed, but radial muscles absent. Mouth cruci form, surrounded by a quad Fig. 1. Ephyra, 2 mm . in diameter. x1.