392 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



It should be noted, however, that while Harvey had erroneously 

 believed that luciferase was not an enzyme but itself the substance 

 oxidized with the production of light, he was probably quite right, 

 owing to facts stated under the topic on the mechanism of light-pro- 

 duction, in believing luciferase to be the main source of light. 



Before we leave the question of the effect of inorganic salts on 

 luminescence, it is of interest to note that NaCl and a number of 

 other salts markedly increase the total amount of light emitted during 

 the reaction of a given amount of luciferin (Anderson, 1937). This 

 may have teleological significance as the luminescent reaction, when 

 produced by Cypridina, takes place in sea water — a salt solution. 

 "One explanation of the increased light emission in solutions of sodium 

 chloride is that a change occurred in the activated molecule which 

 made it less likely to lose its energy in collisions with the solvent or 

 with added potassium iodide or thiocyanate." 



There are luciferins and luciferases. Thus, luciferin from the 

 firefly, Photuris (a lampyrid), will produce light with luciferase from 

 the firefly, Pyrophorus (an elaterid), and vice versa. But the luci- 

 ferin and luciferase of Cypridina, an ostracod, will not luminesce with 

 firefly luciferase or luciferin, respectively (Harvey, 1919, 1928). Luci- 

 ferin of the shrimp, Systellaspis, will not give light with luciferase of 

 the ostracod, Cypridina, nor will Cypridina luciferin luminesce with 

 the luciferase of Systellaspis (Harvey, 1931a) or of the mollusk, 

 Pholas (Harvey, 1919, 1928). Since the luciferases are quite specific, 

 only closely related forms luminesce when their photogens are inter- 

 mixed. (See also Harvey, 1926a). The spectrum is always the same 

 as that of the animal supplying the luciferase. The significance of 

 this has already been pointed out. 



Cypridina luciferin, furthermore, differs from that of the mollusk, 

 Pholas dadylus (Dubois, 1913, 1914; Harvey, 1919, 1928), in that the 

 latter will oxidize with light-production when acted upon by various 

 oxidizing agents (e. g., potassium permanganate, hydrogen peroxide, 

 oxyhaemoglobin, but not with nascent oxygen in the absence of 

 luciferase). Extracts of many nonluminous animals will oxidize 

 Pholas luciferin with light-production, but not so with Cypridina 

 luciferin. "Oxidation of [Cypridina] luciferin at anodes of various 

 metals by nascent oxygen or oxidation by colloidal platinum or 

 palladium and oxygen or other oxidizing agents never results in 

 luminescence in the absence of luciferase." Luciferin, in 95 to 99 

 percent alcohol (in which luciferase is not soluble) will luminesce 

 faintly if heated to 70° C. or if minute amounts of solid KMn0 4 , 

 disuccinyl peroxid, K 3 Fe(CN) 6 PtCl 4 , PdCl 2 , and Ca hypochlorite are 

 added. These facts do not at all imply that, in bioluminescence, 

 luciferin is the source of light since — 



