DEPARTMENT OF MARINE BIOLOGY. 169 



The electro-reduction of oxyluciferin can be brought about at the cathode 

 when a current from an external source is passed through a solution of oxylucif- 

 erin and luciferase, plus some NaCl to render it a conductor. With smooth 

 Pt electrodes, a potential difference of about 1.8 volts is necessary to produce 

 a just-visible luminescence at the cathode, and with 2 volts the light is quite 

 bright. No light appears at the anode. Again we have reduction of oxyluci- 

 ferin by the nascent H formed at cathode and immediate reoxidation of this 

 in presence of the luciferase and dissolved oxygen. 



Molecular hydrogen is unable to reduce oxyluciferin, but will do so in 

 presence of a catalyst, such as palladium. If a sheet of Pd is palladinized, 

 exposed to a hydrogen atmosphere, and then placed in oxyluciferin-luciferase 

 solution, the whole surface of the Pd will glow. Palladinized Pd not exposed 

 to hydrogen, or exposed to oxygen, will not glow. The Pd possesses catalytic 

 action by virtue of some power of converting hydrogen into the active or 

 atomic form. Oxyluciferin is then reduced in a thin layer over the Pd surface 

 and is immediately reoxidized with light production by the luciferase and 

 oxygen in the layer near to the Pd surface. 



It would appear that the reduction of oxyluciferin is a hydrogenation, and, 

 like other hydrogenations, is presumably exothermic. The equilibrium equa- 

 tion would be: 



oxyluciferin + H2 7=±- luciferin -f- x cUl. 



When luciferin oxidizes and is converted to oxyluciferin with dehydrogen- 

 ation, i. e., when the reaction proceeds in the opposite direction, we should 

 require an absorption of heat. However, as the hydrogen is probably removed 

 by combination with the oxygen to form water, we have an exothermic 

 reaction proceeding at the same time, and the total heat production will be the 

 resultant of these two reactions. As one is exothermic and the other endo- 

 thermic, it is possible that the two will balance, and almost no temperature 

 change will occur. 



luciferin = oxyluciferin + H2 — x cal. 



H 2 +0 = H 2 0+58.3 cal. 



No temperature change has thus far been demonstrated with certainty to 

 accompany animal luminescence. 



It should be noted that, by passing hydrogen over a palladinized surface 

 in contact with oxyluciferin, luciferase, and oxygen, we have a means of pro- 

 ducing a continuous luminescence by hydrogenation and dehydrogenation. 

 The final change occurring is the union of hydrogen and oxygen to form water. 

 With a constant supply of oxygen and hydrogen, such a luminescence should 

 continue for an indefinite period, or until the luciferase and luciferin are 

 changed by some secondary reactions. 



It should also be noted that luminous animals need not continuously pro- 

 duce luciferin from some simpler substance, but may utilize their store of lucif- 

 erin again and again, reducing the oxyluciferin, and then reoxidizing, the 

 dominant process dependent on the conditions within the photogenic cell. 

 We thus have great economy in the chemical processes underlying biolumi- 

 nescence, as we have great economy in the physical make-up of animal light, 

 the production of those wave-lengths alone which affect the eye. 



