378 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



cence of organisms (bioluminescence) . Examples of chemilumines- 

 cence in the inorganic world are numerous. Thus, freshly cut Na or K 

 metals form an oxid film accompanied by the emission of light, which 

 is perceptible in a dark room. 



A. DISTRIBUTION AND STRUCTURE OF THE LIGHT-PRODUCING 



ORGANS 



For a treatment of the earlier literature bearing upon this topic, de 

 Kerville (1890), Mangold (1910-14), Harvey (1919), and Pratje (1923) 

 should be consulted. Dahlgren (1915, 1916) has given a semipopular 

 and well-illustrated account of the distribution of light organs in 

 marine invertebrates. It is of interest to note that no truly fresh- 

 water animal has as yet been determined, for certain, to possess a 

 light-producing organ. 



/. Crustacea. — Light-producing organs have been found among the 

 Ostracoda, Copepoda, Schizopoda, and Decapoda. Luminescence in 

 the ostracod, Cypridina hilgendorfii, the principal subject of the 

 Harveiian school is extracellular. The luminescent organ in this 

 animal is composed of maxillary gland cells, each cell opening by a 

 separate pore with a valve (cf. also Kanda, 1920, and the work of 

 Doflein and of Miiller, quoted in the above works). Upon the con- 

 traction of certain muscles, the secretion is forced to the exterior from 

 the saclike reservoir and luminesces in the sea water. In the deep-sea 

 shrimp, Acanthephyra debelis, the light-organs are scattered over the 

 surface of the body. The shrimp, Systellaspis, possesses a large 

 luminous gland which secretes a luminous material into the sea water 

 (Harvey, 1931a). This species occurs at depths between 600 and 800 

 fathoms off the coast of Bermuda. Luminescence at abysmal depths 

 may be useful for illumination, although Kemp (1910) has noted that 

 the vast majority of marine animals possessing photophores (including 

 decapod Crustacea) live at the surface or at intermediate depths and 

 never occur at the bottom, at least in deep water. 



2. Chilopoda (centipedes). — No millipede has as yet been estab- 

 lished to be self-luminous. The centipede, Scolioplanes crassipes (cf. 

 Koch, 1927), emits a vivid green light from its sterna. When it 

 crawls, it leaves behind it a trail of luminous fluid droplets which 

 emit green light. This shows that both the luciferin and luciferase 

 are secreted to the exterior. This would require a perforation at some 

 point in the membrane of each secreting cell, since luciferase is a 

 complex protein (see below). Each light organ of this animal is a 

 large hypodermal cell. A similar condition exists in Geophilus linearis 

 and other members of the order Geophilidae of the class Chilopoda 

 (centipedes). 



Sudden submersion in water, weak induction currents, chloroform, 

 or a rise in temperature of about 10° C. stimulates the production of 

 light in Scolioplanes. 



