Fig. 1.

Development of a medusa from a polyp and the structure of the rhopalium in Aurelia sp. 1 a Polyp. b Strobila. c Ephyra (oral view). d Metephyra (oral view). e Enlarged view of a rhopalium in c. f Enlarged view of a rhopalium in d. g Lateral view of a rhopalium of a metephyra. te tentacle, mo mouth, bc body column, rh rhopalium, la lappet, I prephyra I stage (see text), II prephyra II stage, III prephyra III stage, mn manubrium, ra rhopalar arm, gf gastric flaments, gf/go gastric filaments/gonads, oa oral arm, rc ring canal, lc lithocyst, co pigment-cup ocellus, so pigment-spot ocellus, tp touch plate, gc gastrovascular cavity, ca rhopalar canal, ec ectoderm, en endoderm, te terminal segment, in intermediate segment, bs basal segment