VOL. XV, pp. 213-234 NOVEMBER 20, 1902 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



OBSERVATIONS ON THE CONDITIONS OF LIGHT 

 PRODUCTION IN LUMINOUS BACTERIA. 



BY RANDOLPH E. B. McKENNEY. 



Introduction. 



Although the phenomenon of the production of light by 

 organic or organized matter was known in the days of Aristotle, 

 comparatively little is known concerning the actual conditions 

 of luminescence. The number of organisms or organic bodies 

 said to possess the so-called phosphorescent* properties is a 

 large and varied one. Both animal and plant forms, simple and 

 complex types of life, are to be found in the category of light- 

 producing organisms. 



In view of the comparative ease of culture and simplicity of 

 form, the photogenic bacteria constitute perhaps the best 

 material for the study of luminescence in living forms a 

 phenomenon, the essential conditions of which are probably the 

 same in all forms of life. The study of the conditions of 

 luminescence was undertaken at the suggestion of Prof. Dr. W. 

 Pfeffer and was carried out in the botanical laboratories of 

 Leipzig and Basel. It is a pleasant duty to here give expres 

 sion to my appreciation of the friendly counsels of Professors 

 W. Pfeffer and A. F. W. Schimper during the course of my 

 experiments. 



*The term phosphorescence as applied to the light produced by lumi 

 nous organisms is inappropriate. It should only be applied to light 

 emitted in the dark by bodies which have been previously illuminated. 

 The light emitted by all known luminescent forms of life is entirely in 

 dependent of previous illumination. 



44 BIOL. Soo. WASH. VOL. XV, 1902. (213) 



