1. In the dark adapted Mnemiopsis, mechanical stimulation causes luminescence along the eight rows of paddle plates. The tactile receptors for this reaction lie only in the paddle plate rows, and are connected only longitudinally along these rows. 2. The tactile receptors for ciliary and muscular movement are distributed generally over the surface and are connected by a nerve net. 3. Luminescence may occur at 3°C. provided the animal has been kept sufficiently long at that temperature. Ciliary action goes on at – 0.6°C. 4. Luminescent paper made by spreading the luminescent secretion of Mnemiopsis on filter paper, yields the following effects. The paper shows luminescence in solutions of K2SO4, KCl, MgSO4, SrCl2, CaCl2; no luminescence in NaCl, MgCl2. Changes in pH value of salt solutions between pH 6 and 8 do not affect the phenomenon. Illumination of the paper with strong light for longer time than necessary to suppress luminescence in the living animal has no effect on the subsequent luminescence of the paper. Hence in the animal, light affects luminescence through the photoreceptor system; the nervous system carries the impulse to the luminescent organs. 5. The power of luminescence of the animal is suppressed by sufficiently intense light, the relation between the intensity and the time requisite being expressed by the equation for the Bunsen-Roscoe photochemical law, namely, I · t = K. 6. It is suggested that the reaction scheme involved in luminescence is of the following form See PDF for Equation in which A is the luminescent substance in the resting, dark adapted animal, L is the light-giving decomposition product, and D is a product which does not yield light. 7. The luminescent substance receives double innervation and the character of the decomposition is determined by the type of nerve fiber stimulated.