Ocelli of hydromedusae.
D000818:Animals; D001369:Axons / Q000648:ultrastructure; D003063:Cnidaria / Q000033:anatomy & histology*; D004594:Electrophysiology; D008027:Light; D008854:Microscopy, Electron; D010786:Photoreceptor Cells / Q000033:anatomy & histology* / Q000502:physiology / Q000648:ultrastructure