Abstract
1. The miniature electrical oscillation of the tymbal muscle of the cicada was investigated with the following species: Terpnosia vacua, Platypleura kaempferi, Cryptotympana japonensis, Graptopsaltria nigrofuscata, Tanna japo-nensis, Oncotympana maculaticollis and Meimna opalifera.
2. The miniature electrical oscillation was observed not only in the silent muscle but also in the shrilling muscle. It was observed either in situ or in isolated preparation.
3. The miniature electrical oscillation was not affected by motor innervation but originated myogenically.
4. The pattern of oscillation was usually irregular but sometimes changed to be regular, waxing and waning.
5. The frequencies of two sources which were supposed to compose the beating oscillation were approximately equal to that which was found when the wave was regular.
6. The frequencies of regular and beating discharges were quite comparable to that of the action potentials of respective species in singing.
7. The cause of the transition of the pattern of oscillation was discussed and its similarity to the electrocardiogram of the fibrillation was noticed.
