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Although bioluminescence, in general, presumably depends on the presence of a specific enzyme-substrate system, extracts of heat-labile ("luciferase") and heatstable ("luciferin") components which emit light when mixed (the luciferin-luciferase reaction) have been definitely obtained from only seven1 of the many types of luminescent organisms known, viz., certain bivalves (Pholas, Roceltaria), ostracod crustacea (Cypridina), the marine fireworm (Odontosyllis), deep-sea shrimp (Systellaspis, Heterocarpus, the fresh-water limpet (Latia), fireflies, and bacteria. The one instance in which a luciferin-luciferase reaction has been reported in products of a luminous fish (Malacocephalus laevis)2 is questionable because of the bacteriallike properties of the material and the subsequent cultivation of luminous bacteria from the light organ.3 Luminescence was recently detected (Y. H.) in specimens of a small fish, Parapriacanthus beryciformis Franz,4 in a Shimoda fish market. Common to coastal waters of Japan from Yokohama southward, this fish of the family Pempheridae presents no unusual features externally, and close scrutiny of living specimens at night is needed to observe their luminescence. Internally, two photogenic ducts occur ventrally between the pectoral fins and anus (Figs. 1 and 2) underlying translucent muscle which serves as a lens, as in Acropoma japonicum, Paratrachichthys prosthemius, and several fish of the Leiognathidae.5 Of the two ducts, the more anterior, or thoracic, duct is a V-shaped, thin, white, tubular structure, closed at each end; in appearance it resembles the U-shaped duct of Acropoma japonicum that contains symbiotic luminous bacteria. In a fish of 75 mm. in total length, this duct is approximately 10 mm. long, 1 mm. wide, and 0.2 mm. thick. The more posterior, or anal, duct is filiform, lying mid-ventrally and extending to the rectum, with which it communicates through a small pore. In a 75-mm.-long fish, this duct is about 7 mm. long, 1 mm. wide. and 0.2 mm. thick. By pressing a living specimen between one's fingers, a luminous exudate is forced out of the anus. Attempts to cultivate luminous bacteria, by the usual methods, from the photogenic organs of ten specimens gave negative results. When dissected out, minced, and placed in deionized or tap water, the photogenic organs yield a brightly luminous solution whose light persists for many hours. Luminescence of such solutions is oxygen-dependent, for it is extinguished by evacuating the air and returns when air is readmitted. Preparations of crude luciferase were made in two ways from the luminescent ducts dissected out of about a dozen specimens in each case. The first method consisted merely of grinding the ducts in a mortar and working up the resulting

THE LUCIFERIN-LUCIFERASE REACTION IN A FISH, PARAPRIACANTHUS BERYCIFORMIS, OF NEWLY DISCOVERED LUMINESCENCE