THE CHEMISTRY OF LIGHT PRODUCTION 103 



oxygen, and a photogenic substance were necessary for 

 light production, 



A very great advance in our knowledge of the chemis- 

 try of the problem was made by Dubois in 1885. He 

 showed that if one dips the luminous organ of Pyrophorus 

 in hot water, the light disappears and will not return again. 

 Also if one grinds up a luminous organ the mass will 

 glow for some time but the light soon disappears. If one 

 brings the previously heated organ in contact with the 

 unheated triturated organ it will again give off light. 

 Later, Dubois showed that the same experiment could 

 be performed with the luminous tissues of Pholas dacty- 

 lus. A hot-water extract of the luminous tissue, and a 

 cold-water extract of the luminous tissue, allowed to stand 

 until the light disappears, will again produce light if mixed 

 together. Dubois (1887 b) advanced the theory that in 

 the hot-water extract there is a substance, lucif erin, not 

 destroyed by heating, which oxidizes with light produc- 

 tion in the presence of an enzyme, luciferase, which is 

 destroyed on heating. The luciferase is present together 

 with lucif erin in the cold-water extract, but the lucif erin is 

 soon oxidized and luciferase alone remains. Mixing a 

 solution of lucif erin and luciferase always results in light 

 production until the lucif erin is again oxidized. Similar 

 substances have been found by me in the American fireflies, 

 Photinus and Photuris, the Japanese firefly, Luciola, and 

 in the ostraood crustacean, Cypridina hilgendorfii. 

 Crozier ^ reports that they exist also in Ptychodera, a 

 balanoglossid. I have been unable to demontrate their 

 existence in luminous bacteria; in the annelid, CJuetop- 

 terus; the pennatulids, Cavernularia and Pennatula; the 



^ Private communication. 



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