As preparations Scyphistoma of Chrysaora, with four perradial tentacles and horny basal perisarc.
As the scyphistoma grows the tentacles increase in number, four interradial and eight adradial being formed in addition to the four primary perradial tentacles (fig.
The sixteen tentacles of the scyphistoma disappear, and in the place of the four perradial and four interradial tentacles, the eight tentaculocysts of the adult are formed as outgrowths of the subumbral margin, independently of the tentacles of the scyphistoma (Friedemann).
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.
On the other hand, such a form as Lucernaria or Haliclystus may be regarded simply as a scyphistoma which has become adult and mature.
The larva after fixation changes into a polyp-like organism termed a scyphistoma or scyphopolyp (fig.
Hence the absence of sense-organs in the scyphistoma does not necessarily disprove its medusoid character, while its anatomical structure resembles that of a simple scyphomedusa, such as Lucernaria, rather than that of a polyp.
The single ephyra carries the sixteen scyphistoma tentacles, which will atrophy and disappear.
The internal gastric cavity of the scyphistoma is not a simple space as in the hydropolyp, but is subdivided by four ridges or taeniolae, arising one in each interradius (fig.
D, First constriction of the Aurelia scyphistoma to form the pile of ephyrae or young medusae.