THE CHEMISTRY OF LIGHT PRODUCTION 105 



material of Cypridina with sucli oxidizing agents as 

 KMn04, H2O2, blood and H^Oa, BaO^, etc., I called the 

 heat resistant substance of Cypridina, " photophelein" 

 (from phos, 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 

 {=Pholas 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 



