1. Pelagia noctiluca responds to galvanic stimulation by a luminescent glow at the anode. If placed near the cathode a secondary glow occurs also on the cathodal side. 2. The luminescent slime of Pelagia when subjected to the galvanic current glows around the cathode. This is referred partly to the movement of hydrogen bubbles, but in the main to the alkali formed at the cathode. 3. The cause of galvanic stimulation in Pelagia is ionic. (1) Anodal stimulation is referred to the blocking of positive ions by the tissue on that side. (2) Cathodal stimulation, when the animal lies near the cathode, is due to the diffusion of alkali outward from a region of high concentration (the cathode). 4. Only the margin of the bell is excited to luminescence by the galvanic current. It is therefore concluded that nervous elements are the seat of excitation. 5. Luminescence is not a result of muscular contraction, since K ion causes relaxation of musculature but a continuous luminescent glow in Pelagia. The galvanic current causes pulsations of the bell (contraction and relaxation of the musculature) but a continuous glow.