Studies on the Amount of Light

Interest has centered for a long time on the intensity and efficiency of animal luminescence, not only from a theoretical but also from a practical standpoint. With the exception of the beetles, most luminous animals emit light in such small amounts that adark-adaptedeye is required to register their intensities. I t is a difficult matter to measure accurately low light intensities, especially when they are intermittent as in certain luminous organisms. The intensities of Cypridina, however, are sufficiently bright to measure. Harvey, 1925, has successfully measured the amount of light and over-all luminous efficiency of dense emulsions of luminous bacteria, and finds that they are 0.156 per cent efficient. As is well known the light production in Cypridina is an oxidation process, due to the oxidation of a substrate, luciferin, in the presence of a catalyst, luciferase, and follows the laws of enzyme action. After mixing luciferin and luciferase solutions a gradual decrease of luminous intensity follows the initial marked brilliancy. Studies of these decay curves by Amberson by a photographic method show that the light intensities are continually and gradually falling off. In general the effect of the enzyme, luciferase, is proportional to its concentration. Amberson's curves show that the reaction velocities follow this law, i.e. the velocity constant is proportional to the concentration of the enzyme. Amberson assumed after Trautz tha t , " . . . . if light intensity at any instant is assumed to be proportional to reaction velocity at that instant, the decay curve of the light produced in the course of the luminescent reaction in Cypridina is, after the first second, in com-