106 THE NATURE OF ANIMAL LIGHT 



designate the luciferins and luciferases from different 

 animals by prefixing* the generic name of the animal and 

 speak of Pliolas luciferin, Cypridina luciferase, Pyro- 

 phorus luciferase, etc. In extracts of many non-luminous 

 animals Dubois has found oxidizing agents which can 

 oxidize Pholas luciferin with light production and I have 

 confirmed this for Pliolas, but I have not found any such 

 substances in non-luminous animals which will oxidize 

 Cypridina luciferin with light production. I have found 

 in extracts of non-luminous animals substances which will 

 liberate the bound luciferin in a concentrated Cypridina 

 luciferase solution. The luciferin can then be oxidized 

 by the luciferase and light appears. Their effect is similar 

 to that of salt crystals and I suggest that they be called 

 photoplieleins, substances that assist in the luciferin-luci- 

 f erase reaction by liberating bound luciferin. One of the 

 best ways of freeing a solution of luciferase from bound 

 luciferin is to shake with chloroform. We can then do 

 away with the disturbing effects of bound luciferin. 



It is obvious that luciferin must be formed from some 

 precursor in the cell and following the usual biochemical 

 terminolog}^, Dubois has called it proluciferin or preluci- 

 ferin, and believes that it is converted into luciferin by 

 an enzyme co-luciferase. The experiments to prove the 

 existence of proluciferin were first made by Dubois on 

 Pholas in 1907 and have since been amplified (1917 a; 

 1918 a and 6). 



In order to understand these experiments it must be 

 borne in mind that Dubois prepares luciferin from Pholas 

 in three ways: (1) By precipitating the viscid luminous 

 fluid from the siphons with 95° alcohol and dissolving the 

 precipitate in water (1901a, 1907). (2) By extracting 



