142 THE NATURE OF ANIMAL LIGHT 



it behaves in many ways like an enzyme and may be 

 so regarded. 



Luciferin, on the other hand, is not digested by pro- 

 teolytic enzymes, is dialyzable, almost but not completely 

 precipitated by saturation with (NH4)2S04, and is solu- 

 ble in absolute alcohol, acetone, and some other organic 

 solvents, but not in the strictly fat-solvents like ether, 

 chloroform, and benzol. There are, however, certain 

 CO-NH linkages which are not attacked by proteolytic 

 enzymes and some peptones soluble in absolute alcohol, 

 so that these two characteristics do not bar it from the 

 group of proteins. Luciferin, in fact, has many proper- 

 ties in common with the proteoses and peptones but its 

 chemical nature cannot be definitely stated at present. 



