DYNAMICS OF LUMINESCENCE 157 



is quite blue. The weaker light at temperatures above the 

 optimum is also more yellow in color. I believe this dif- 

 ference in color is a function of the slowed reaction veloc- 

 ity, for a mixture of luciferin and luciferase which gives 

 a bluish luminescence at room temperature, will give a 

 weaker and yellowish luminescence if diluted with water. 

 Dilution with water will slow the reaction velocity. If the 

 difference in color were not real but due to change in color 

 sensitivity of the eye with different intensities of such 

 relatively weak light (Purkinje phenomenon), the weaker 

 light should appear more blue. As the weaker light 

 appears more yellow, I therefore believe the color differ- 

 ence is actual and not subjective. 



A minimum, optimum, and maximum temperature for 

 luminescence is observed in all luminous organisms. The 

 minimum is usually very low. Luminous bacteria will still 

 light at -11.5° C. The power to luminesce under ordinary 

 conditions is not destroyed by exposure to liquid air, for, 

 on raising the temperature, light again appears (Mac- 

 fayden, 1900, 1902). Almost all organisms will luminesce 

 at 0° C, and the luminescence minimum probably repre- 

 sents the point at which complete freezing of the luminous 

 solution occurs. It is very low with bacteria because they 

 are solutions in capillary spaces of very small size, a 

 condition tending to lower the freezing point. 



The luminescence maximum represents the point at 

 which luciferase is reversibly changed so as to be no 

 longer active. If the temperature is again lowered the 

 luciferase again becomes active and light reappears. 

 Some degrees above this, and in all forms well below the 

 boiling point, luciferase is coagtilated and destroyed. 

 As the coagulation point of proteins depends on many 



