DYNAMICS OF LUMINESCENCE 155 



and completely saturated at pressures of oxygen well be- 

 low the pressure of oxygen in air (152 mm. Hg). As the 

 optimum oxygen tension for luminescence of luciferin is 

 also well below that of air, mixtures of luciferin and luci- 

 f erase luminesce with equal brilliancy whether air or pure 

 oxygen is bubbled through them. To obtain an excess of 

 oxygen it is only necessary to keep the solution saturated 

 with air and statements regarding concentration of lucif- 

 erin and luciferase and intensity or duration refer to 

 excess of oxygen. Investigators who have studied the 

 effect of increase in oxygen pressure on luminous animals 

 have come to the same conclusions. High pressures of 

 air or oxygen do not increase the intensity of luminescence 

 (Dubois and Regnard, 1884). 



The hydrogen ion concentration of crude solutions of 

 luciferin and luciferase, made by extracting whole Cypri- 

 dinas with hot or cold water is fairly constant, about 

 Ph = 9, determined electrometrically. Such solutions 

 have a high buffer value and the Ph does not change 

 during oxidation of luciferin so that this variable is auto- 

 matically controlled. 



Because of difficulties in measuring low intensities of 

 light which are constantly changing, no figures on light 

 intensities can be given, but it is easy to establish the fol- 

 lowing facts : The greater the concentration of luciferin 

 or luciferase the more intense the luminescence. The 

 greater the concentration of luciferin the longer the dura- 

 tion of luminescence and the greater the concentration of 

 luciferase, the shorter the luminescence lasts. Thus, if we 

 mix concentrated luciferin and weak luciferase we get a 

 bright light which lasts for a half hour or more, gradually 

 growing more dim. Concentrated luciferase and weak 



