[Observation on the structure of the statocysts of decapods]

Light microscopical observation of serial sections of four kinds of decapoda which living in seas around Japan (Ommastrephes sloanei pacificus, Sepia esculenta, Doryteuthis bleekeri, Sepioteuthis lessoniana) was carried out. These specimens were fixed alive with 10% formaldehyde solution diluted with sea water and then dehydrated without decalcification with ethylalcohol diluted with sea water. After embedding in 6% celloidin, the specimens were cut into 30 microns thick and sections were stained with hematoxilineosin. Under light microscopic observation, the maculae, statoconial layers, cristae, cupulae, statoliths, central nervous system and static nerves were well preserved. The statocysts of all four decapod species were similar in shape. Color photographs of horizontal sections of the head, statocysts, processes, gravity recepter systems, angular acceleration receptor systems, statoliths and nerve fibers with the central nervous system of these four decapod species are shown.