The Chemistry of Light-Production in Luminous Organisms. 179 



of the corresponding substances in the two animals. A more complete 

 table is given on page 200. 



Whatever the exact interpretation of the facts may be, it is certam 

 that two substances are concerned in light-production, and these may be 

 separated, because they are destroyed at different temperatures. We 

 may now inquire into each of their properties separately and return to 

 a discussion of the mechanism of hght-production, in considering the 

 possible enzyme nature of photogenin. 



Table 1. 



DISTRIBUTION OF PHOTOPHELEIN AND PHOTOGENIN IN ORGANISMS. 



Certain fundamental facts for the chemical theory of light-production 

 appear when we study the distribution of photophelein and photogemn : 

 (i) in the non-luminous parts of Cypridina; (ii) in the non-luminous 

 Cypridina; (in) in other non-luminous organisms; (iv) in luminous 

 organisms. 



By a careful, quick scissors-cut, the head end of Cypridina containmg 

 the luminous gland can be separated from the posterior half without 

 any contamination of the latter with luminous secretion. If we now 

 test the non-luminous half with dilute photophelein and photogenin, 

 we find that it contains nothing which will give light with photophelein, 

 but something which will give a bright light with photogenin. We 

 must try the experiment immediately, because this substance disappears 

 if the extract stands in presence of oxygen. In absence of oxygen, or 

 if the extract is boiled immediately (but not too long a time), the sub- 

 stance does not completely disappear, even after an hour. There is, 

 therefore, in the non-luminous parts, the substance photophelein, 

 which disappears even in the absence of photogenin (from luminous 

 gland), unless the solution be boiled or oxygen excluded. (Note the 



