When tests are applied and precipitating reagents are added to crude luciferin and crude oxyluciferin solution, they give identical results in each case. A more complete account of the chemistry of luciferin has been given in this chapter, and there is no need of duplicating these statements regarding oxyluciferin. Like luciferin, the oxyluciferin will pass porcelain filters, dialyze through parchment or collodion membranes, and is undigested by salivary diastase, pepsin HCl, Merck's pancreatin in neutral solution, and erepsin. The salivary diastase and the pancreatin (containing amylopsin, trypsin, and lipase) were allowed to digest for four days at 38° C. without showing any evidence of digestive action. 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 luciferin 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 solution. 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, speculation regarding it can be of little value. SUMMARY 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 shown 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 luciferins and luciferases from different 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 _Pholas_ luciferin in that it can not be oxidized with light production by KMnO_{4}, H_{2}O_{2}, with or without hæmoglobin, or similar oxidizing agents. _Cypridina_ luciferase differs from _Pholas_ and firefly luciferase in that it is not readily destroyed by the fat-solvent anæsthetics, such as chloroform, ether, etc.