The experiments were carried out in the small pool with electrode upon slide-galss. The results are as follows. 1) Strength-duration curve of the electrical stimulation for Paramaecium coincide very well to the rectangular hyperbola i.e. it follows to the excitation law for the muscle or nerve of frog. 2) Not only the slightest excitation of Paramaecium but also the death by electrical shock follows to this rule. 3) The cause of death by electrical shock appears to be alkalinity in the neighbourhood of the cathode pole. 4) Alternating current, if its interval is short enough for the intensity of the current, does not stimulate Paramaecium or not cause death. 5) But alternating current, if rectified, even high frequency-current like Tesla cause excitation or death of Paramaecium.