DYNAMICS OF LUMINESCENCE 161 



Photinus luciferin X Photinus lucif erase = red- 

 dish light. 

 Photinus luc'derin X Photuris lucif erase = yel- 

 lowish light. 

 Photuris luciferin X PJwturis lucif erase = yel- 

 lowish light. 

 Photuris luciferin X Photinus luciferase = red- 

 dish light. 

 Thus the color of the light in these ''crosses'^ is that 

 characteristic of the animal supplying the luciferase. To 

 bring this fact in line with what we have already said 

 regarding reaction velocity and luminescence, we must 

 believe that the Photinus luciferase oxidizes at a slower 

 rate than the Photuris luciferase. In this connection it is 

 of interest to recall that the Photuris light as emitted by 

 the insect becomes reddish at high temperatures, or if the 

 insect is plunged into alcohol, both conditions which bring 

 about partial coagulation of the luciferase and reduce its 

 active mass. 



