I30 



THE AMERIC. LV .V l TURALIsr. [X ol. XXXVIII. 



of lophin, discovered a series of carbon compounds similar to 

 those found in living organisms and cai)able of becoming lumin- 

 ous under conditions compatible with life. The conditions nec- 

 essary for this production of light he found to be the presence of 

 oxygen, an alkaline reaction and slow chemical action. Watase 

 ('96) states that in the firefly the phenomenon is due to the oxi- 

 dation, in alkaline media, of a granular substance secreted by 

 the cells of the photogenic tissue. He offers no further sugges- 

 tion as to the character of the substance than that it is "a secre- 

 tion of fatty nature." He gives as proof of the oxidation theory 

 the fact that when the photogenic material is crushed on a slide 

 and lowered into a jar of carbon dioxide the light disappears 

 instantly, but reappears when the slide is placed in a jar of oxy- 

 ,L;cn, or simply in the air. This may be repeated se\ cral times 

 with the same material. Watase recognizes the necessity of 

 moisture as well as of oxygen in the process of photogeny. 



Dubois stands almost alone in opposing the theory of oxida- 

 tion. As a result of experiments with ozone, nascent oxygen 

 and oxygenated water he states ('95), that the action of ener- 

 getic oxidizing reagents at once and finally extinguishes the 

 light, without first causing any increase in brilliancy. How- 

 ever, the absence of oxygen seems to destroy the light, as it is 

 suspended when the light-organs are placed in a vacuum. From 

 his earlier work he concluded that the light was the result of a 

 process of crystallization. His later work ('98^) has led him to 

 abandon this theory. He still rejects the oxidation hypothesis 

 as crude and unscientific, and offers in its place one of a reaction 

 iK'twccn two substances to which he has given the names luci-- 

 tviasc and luciterine. The accessibility of the material led him 

 to use IViolas dactylus, a marine mollusk, as the basis of his 

 study. The inner wall of the siphon of a large Pholas was 

 M raped with a knife and the resulting pulp crushed with sand 

 j'"^'^ 1^3'/ al^-'>hol. After twelve hours it was filtered and a 



agitation with air. The alcohol was drained off from the resi- 

 due and chloroform atlded. After some hours a second non- 

 lu^llllou^ liquid was filtered off. A mixture of one part of the 

 ^ist lunud with three parts of the second gave a beautiful 



