Mclvenney — On Lutninoiis Hacteria. 215 



theory of the vital nature of luminescence. However, these observers 

 hold that inasmuch as no luminous substance has ever been isolated 

 from photobacteria, luminescence must be insei^arablo from life. Lud- 

 wig, and with him Dubois, is of the opinion that the light is produced 

 by some specific substance, simikir to those discovered by Kadzis/.ewski. 

 As tlie matter rests now, there is almost as much evidence for the 

 "luminous substance" theory as for the intracellular vital theory; the 

 latter having, however, slightly the better of the argument. In order to 

 come a little nearer to the cause of light production, I decided to ex- 

 amine more minutely into the nutrition of the jliotobacteria and the 

 effect of various external agents on the light product ioa. 



Material. 



Most of the succeeding observations and experiments were made with 

 Bacillus pJiosphorescens, B. Fischer {Photuhacteriunt indicuiii, Beij.) and 

 Microtipira luminosa, (Beij.) Mig. {PJi. liiniinusam Beij.). Some experi- 

 ments were also made with /j'/c/^t/uw ])hosphor('i<ccns, ]\. Fischer, {P/i. 

 pJioxpJurrescens, Beij.). Cultures of these species were obtained from 

 Krai's laboratory in Prague. The culture of Microspira luminosa thus 

 obtained emitted a weak light. Strongly luminous cultures of this 

 species were obtained, however, through the kindness of Prof. Dr. 

 Beijerinck, of Delft. 



The morphologic characters of the above mentioned species are quite 

 fully set forth in the papers of Beijerinck and in Migula's "System der 

 Bakterien." It may simply be noted here that the Bacillus and Micro- 

 spira are motile and liquefy gelatine, while the Bacterium is non-motile 

 and does not liquefy gelatine. When not otherwise indicated the results 

 recorded will refer to BaeilluH phosphm'escens. 



Genera! Methods of Culture. 



For most of the experimental work a liquid culture medium was found 

 best, but control experiments were frequently made with solid culture 

 media. About 500 grams of fresh fish were extracted over a water bath 

 with two litres of water. Herring, pike and carp yielded good extracts, 

 but that obtained from a couple of species of flounder was decidedly less 

 favorable to both growth and light production. To the filtered fish ex- 

 tract the following ingredients were added: 



Peptone 1.0^ 



Asparagin .5^ 



Glycerol 2.0^ 



Na CI 2.0^ 



Mg CW \.H 



The liquid thus obtained was made weakly alkaline with Na OH, and 

 constitutes what will later be designated as normal fish bouillon. Ap- 

 propriate solid media were obtained by adding to this bouillon either 1^ 

 of good agar or 6 to 8^ of best grade gelatine. 



As containers for the bouillon, Erlenmeyer flasks of ca. TOO c. c. 

 capacity were employed. From 10 to 20 c. c. of the bouillon was intro- 

 duced into each flask. The broad base of the flask at once insured 



