Novembee 3, 1916] 



SCIENCE 



653 



substance alone in solution is non-luminous 

 and fairly stable. On this theory, therefore, 

 the luciferin is the source of the light and, 

 according to Dubois, Pholas luciferin will give 

 light on oxidation with Kiln0 4 , blood, IL0 2 

 and similar oxidizing agents. He found also 

 substances (luciferase) in the blood of various 

 marine molluscs and crustaceans which would 

 give light with Pholas luciferin, but the latter 

 he found only in the luminous organs of 

 Pholas dactylus. 1 



Since the publication of my previous paper, 

 I have investigated very thoroughly the chem- 

 istry of light production in five different 

 forms : 2 the Japanese fire-flies, Luciola parva 

 and L. vitticollis; an ostracod crustacean, 

 Cypridina hilgendorfii; a squid, Watasenia 

 scintillans ; a pennatulid, Cavernularia haberi; 

 and the protozoan, Noctiluca miliaris. Wata- 

 senia, Cavernularia and Noctiluca will not 

 give the luciferin-luciferase reaction despite 

 the most favorable conditions and many at- 

 tempts to demonstrate it. These organisms 

 need not be considered at present, as there are 

 many reasons why the luciferin-luciferase re- 

 action might fail. 



Cypridina and Luciola both contain bodies 

 similar to luciferin and luciferase, but in 

 these forms the production of light differs in 

 very essential points from that described by 

 Dubois in Pholas, and I have come to quite 

 different conclusions regarding the nature of 

 the substances concerned. "We may conveni- 

 ently use Dubois's terminology for the present. 

 First, in Cypridina and Luciola, it is the luci- 

 ferase which is found only in the luminous 

 cells, and luciferin is widely distributed in 

 non-luminous forms. Second, I have been 

 unable to oxidize luciferin with light produc- 

 tion by Klln0 4 or other oxidizing agents. 

 Third and most important, Cypridina luci- 

 ferase will give light with substances (INaCl 

 crystals, thymol, butyl alcohol, saponin), some 

 of which could not possibly be oxidized. The 



i Dubois, B., Annates de I. Soc. Linn, de Lyon, 

 1913 and 1914. 



- Studies made in Japan under the auspices of 

 the department of marine biology, Carnegie In- 

 stitution of Washington. 



luciferase and not the luciferin is therefore 

 the source of the light. Instead of luciferin 

 oxidizing with light production through the 

 catalytic action of luciferase, luciferin is a 

 body assisting in the evolution of light from 

 luciferase. I therefore propose the new names 

 of photogenin (light producer from phos, 

 light, and gennao, to produce) for luciferase, 

 and photophelein (light assister from phos, 

 light, and opheleo, to assist) for luciferin, to 

 indicate more clearly the nature of the light- 

 producing process. Cypridina photophelein 

 (= luciferin) in addition to its thermostabile 

 property is easily dialyzable, while photogenin 

 (= luciferase) is not. Da these points and 

 some others, the system resembles and may be 

 compared to the zymase system (enzyme and 

 coenzyme) of yeast cells. 3 As in so many 

 other biological reactions an easily diffusible 

 thermostabile substance (coenzyme) and a 

 difficultly diffusible thermolabile substance 

 (zymase) are concerned. 



The light-producing power of photogenin 

 and photophelein is very extraordinary. 

 Cypridina photogenin will give visible light 

 with photophelein in one part to 1,600,000,000 

 parts water. Even this is an underestimate, as 

 we do not know the concentration of pho- 

 togenin in the luminous cells apart from pro- 

 teins, water, etc. In the small amounts nec- 

 essary to produce light and in destruction by 

 boiling, photogenin resembles an enzyme but 

 differs in the fact that it is used up in the 

 reaction. Experiment has shown that it takes 

 photophelein from one hundred Cypridinas to 

 use up the photogenin from one Cypridina. 

 Perhaps the fact that photogenin is used up 

 is not sufficient evidence to condemn it as an 

 enzyme since many enzymes are poisoned or 

 destroyed by reaction products; nevertheless 

 I have deemed it best for the present to avoid 

 the termination ase. 



Cypridina and the firefly differ from Pholas 

 in the points enumerated above and agree in 

 most properties with each other, but with 

 some exceptions. Eor instance, firefly photo- 

 genin is readily destroyed by chloroform or 



3 Harden, A., and Young, W. J., Proc. Boy. Soc, 

 B, 77, 405, 1906, and 78, 369, 1906. 



