140 THE NATURE OF ANIMAL LIGHT 



As luciferin is so easily oxidizable a substance, we 

 should expect to find that it will reduce just as glucose 

 will reduce. However, a concentrated solution of lucif- 

 erin has no reducing action on Fehling's (alkaline Cu), 

 Barfoed's (acid Cu), Nylander 's (alkaline Bi) or Knapp's 

 (alkaline Hg) reagent. Glucose will reduce methylene 

 blue in alkaline (not in neutral solution), but luciferin 

 will not reduce methylene blue in alkaline or neutral solu- 

 tion. It would seem, then, that luciferin must contain 

 no aldehyde group. If so, we should expect to obtain 

 reduction of some of the above reagents. Just what group 

 is concerned in the oxidation is unknown at the present 

 time, and in the absence of more experimental data, specu- 

 lation regarding it can be of little value. 



SUMMAEY 



In summing up we may say that the luminescence of 

 at least three groups of luminous animals, the beetles, 

 Pholas, and Cypridina, has been definitely shoAvn to be 

 due to the interaction of two substances, luciferin and 

 luciferase, in presence of water and oxygen. Luciferin 

 and luciferase have quite different properties and may be 

 easily separated from each other by various chemical 

 procedures. As the lucif erins and lucif erases from differ- 

 ent luminous animals have somewhat different properties, 

 they may be designated by prefixing the generic name of 

 the animal from which they are obtained. 



Cypridina luciferin differs from Pliolas luciferin in 

 that it can not be oxidized with light production bj^ 

 KMnO.,, H^Og, with or without haemoglobin, or similar 

 oxidizing agents. Cypridina luciferase differs from 

 Pholas and firefl}'' luciferase in that it is not readily 



