THE CHEMISTRY OF LIGHT PRODUCTION 105 



material of Cypridina with such oxidizing agents as 

 KMnCi, H0O2, blood and H0O2, BaOo, etc., I called the 

 heat resistant substance of Cypridina, ^^ photophelein'* 

 (from plios, light and opheleo, to assist), comparable to 

 co-zymase, and the heat sensitive substance of Cypridina, 

 ^^photogenin" (from phos, light and gennao, to produce), 

 comparable to the zymase proper of yeast. In mode of 

 preparation and properties, the photophelein of Cypri- 

 dina was also comparable to the luciferin of Pholas and 

 the photogenin of Cypridina to the luciferase of Pholas. I 

 also regarded photogenin as the source of the light (hence 

 the name), because a solution of Cypridina photogenin 

 {=PJiolas luciferase) will give light on mixing with crys- 

 tals of salt and other substances which could not possibly 

 be oxidized. I later found, however, that this result was 

 due to the fact that the photogenin solution contained some 

 of the thermostable substance (luciferin) bound (com- 

 bined or adsorbed), and that this was freed by the salt 

 crystals and oxidized with light production. I have conse- 

 quently abandoned the view that the system of substances 

 concerned in light production is similar to the zymase — 

 co-zymase system of yeast — and have adopted Dubois' 

 term, luciferase {=photogenin) for the thermolable ma- 

 terial, and luciferin {=photophelein) for the thermo- 

 stable material. 



The luciferin of Cypridina differs from that of Pholas 

 in that it will not oxidize with light production with any 

 oxidizing agents that I have tried, and will give no light 

 with luciferase from Pholas. It does, however, oxidize 

 spontaneously in solution, although no light accompanies 

 this oxidation. 



I believe that for accuracy and definiteness we must 



