THE CHEMISTRY OF LIGHT PRODUCTION 115 



tacea. 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 (NH4)2S04. It is not 

 precipitated by NaCl, MgS04 ^^ acetic and carbonic acids, 

 except in presence of neutral salts. It forms an insoluble 

 alkali albumin with NH4OH. 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 de- 

 scribes lucif erin as a natural albumin having acid proper- 

 ties. It occurs only in luminous, not in non-luminous ani- 

 mals, 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. 



Pholas luciferase. — Pholas luciferase has all the 

 properties of an enzyme, is destroyed at 60° C, is non- 

 dialyzable, insoluble in fat solvents, but forms a colloidal 

 solution in water. It is not affected by 1 per cent. NaF 

 but its activity is suspended in saturated salt solutions, 

 sugar or glycerine, and it may be preserved in this way, 

 its activity returning on dilution. It is digested by tryp- 

 sin and slowly destroyed by the fat solvent anaesthetics, 

 such as chloroform. For this reason Dubois regards it as 

 an oxidizing enzyme similar to the oxydones of Batelli and 

 Stern. Because he found iron in an extract of Pholas 

 dialyzed for a long time against running water, Dubois 

 considers that it is associated with iron, and reports that 

 it will oxidize the ordinary oxidase reagents, such as 

 pyrogallol, gum guaiac, a-naphthol and para-phenylene- 

 diamine, etc. It remains to be proved, however, that 

 luciferase and not the oxidizing systems such as occur in 



