BIOLOGY OF LIGHT PRODUCTION — MALUF 391 



presence of at least two distinct substances. The substance in the 

 residual solution was destroyed at temperatures of 60° C. or above 

 and was insoluble in petroleum-ether or benzene. The substance in 

 the dialysate was relatively thermostable and soluble in water, petro- 

 leum-ether, and benzene. Dubois termed the substance in the 

 dialysate, luciferin; and that in the residual solution lucif erase, since 

 he soon discovered that the latter substance exhibited the properties 

 of an enzyme — i. e., a protein with catalytic properties. 



As first observed by Spallanzani (1794) on luminous medusae, 

 water is necessary for bioluminescence. Kastle and McDermott 

 (1910) dried the photogenic material of a firefly in vacuo over con- 

 centrated sulphuric acid. In the dry state no light was emitted. 

 After keeping the material quite dry for over 13 months luminescence 

 was produced upon moistening with water. Similar results were 

 obtained by Harvey (1916a) on Cypridina hilgendorfii. In 1918 

 Harvey dried Cypridina rapidly and stored the product. In 1928, 

 when this was powdered and moistened, the luminescence was as 

 intense as in 1918. Even in aqueous solution, if auto-oxidation was 

 impeded, luciferin was noted to remain stable for at least 4 years. 

 Luciferase in solution saturated with NaCl deteriorates more rapidly 

 (Harvey, 1928a). 



There was a time when Harvey (1916a, d) contradicted Dubois' 

 work at its very foundations by considering that luciferase itself is the 

 source of light and is not an enzyme causing light production by the 

 oxidation of luciferin. Harvey's statements grew from experiments 

 in which light was obtained from Cypridina luciferase by substances 

 incapable of oxidation (e. g., pure NaCl, MgS0 4 , chloroform, ether, 

 and pilocarpin — all in aqueous solution) which were believed to act 

 as substitutes for Luciferin. Harvey thereby adopted new names after 

 deciding that those of Dubois were unfit: (1) "Photogenin" (= 

 luciferase of Dubois), or the light-producer; and (2) "photophelein" 

 (= luciferin of Dubois), or light assister. Upon further work with 

 Cypridina, however, Harvey (1918) readopted Dubois' terms of 

 luciferin and luciferase. Harvey's error in this matter lay in his 

 preparation of a luciferin-"free" solution. He allowed a luciferin- 

 luciferase solution to stand in air till all light ceased, when he assumed 

 that the luciferin was consumed, for light was not produced until 

 further luciferin was added. Upon the addition of NaCl, MgS0 4 , 

 ether, or chloroform (a fine array of diverse substances) to the solution 

 in which the luciferin was supposedly consumed, light was again 

 produced. He later found that a luciferase solution separated from 

 luciferin by dialysis did not act in this manner (see also Kanda, 1920) 

 and therefore concluded that luciferin probably consists of two sub- 

 stances, one of which is set free to be acted upon by luciferase when 

 sodium chlorid, magnesium sulphate, ether, or chloroform are added. 



