Since Radziszewski's experiments on the oxidation of oils in alcoholic solutions of alkali, most of the early workers on Bioluminescence tacitly assumed that the oxidizable material was fat or a fat-like substance. Support was given to this view by the occurrence in cells of granules or globules from which the light was seen to come. We now know that these bodies are not fat droplets and that neither luciferin nor luciferase are soluble in such fat solvents as ether, chloroform, benzol or benzine. Phipson's description of the properties of noctilucin are too crude and inaccurate to be considered. Dubois did not study the chemical properties of luciferin and luciferase from _Pyrophorus_, the first form with which he worked, except to point out that _Pyrophorus_ luciferase was destroyed on heating and was precipitated by alcohol while the _Pyrophorus_ luciferin was not so affected. Luciferin was found only in the luminous organ of _Pyrophorus_, not in the blood; luciferase probably exists throughout the animal.[8] [8] Private communication from R. Dubois. PHOLAS LUCIFERIN.--In a series of papers since 1887 Dubois has studied the chemical properties of _Pholas_ luciferin and _Pholas_ luciferase. He finds the luciferin to be destroyed above 70° C., to dialyze slowly, to oxidize with light production in the presence of _Pholas_ luciferase, KMnO_{4}, H_{2}O_{2}, hæmatine and H_{2}O_{2}, BaO_{2}, PbO_{2}, hypochlorites, and the blood of various marine mollusks and crustacea. It is insoluble in fat solvents but forms a colloidal solution in water from which it is precipitated unchanged by picric acid, alcohol at 82°, and (NH_{4})_{2}SO_{4}. It is not precipitated by NaCl, MgSO_{4} or acetic and carbonic acids, except in presence of neutral salts. It forms an insoluble alkali albumin with NH_{4}OH. Dubois (1887 _a_) stated at one time that it could be crystallized and has spoken of it as belonging to several different classes of substances, proteose, nucleoprotein, albumin. Most recently he describes luciferin as a natural albumin having acid properties. It occurs only in luminous, not in non-luminous animals, and is found in all parts of the mantle, especially the siphons. It does not occur in non-luminous parts of the mollusk. No photographs of luciferin crystals have ever been published.