LIGHT PRODUCTION BY LUMINOUS BACTERIA. 



309 



It will be noted from the above Table I. that the bacteria cease 

 to give off light and experiment shows that they are killed by too 

 great dilution with water. That this effect is not entirely due to 

 the absence of salt but is chiefly due to a cytolysis through 

 lowered osmotic pressure is shown by diluting the sea water with 

 an inert iso tonic solution, cane sugar. Some salt is necessary 

 for the continued production of light as the bacteria no longer 

 glow after twenty four hours' emersion in w-sugar, a fact of no 

 great surprise as unicellular freshwater luminous animals are 

 unknown. 



TABLE II. 



EFFECT OF ACID AND ALKALI. 



1 Probably due to neutralization of alkali through absorption of COa. 



As was to be expected acids and alkalies prevent light emission 

 in very weak concentration, the acids in much weaker concentra- 

 tion than the alkalies. In fact the bacteria are very sensitive to 

 acid and will not even phosphoresce with any brilliancy in a 

 neutral medium. 



The organic acid (valerianic) and alkali (methyl amine) have 

 less effect than the inorganic, a result at variance with my results 

 for other organisms which are usually affected more readily by 

 the weak than by the strong acids and alkalies. 1 



1 Harvey, E. N., "Studies on Acids," in Carnegie Institution Publications 

 No. 212, p. 143, 1915; on alkalies, id., No. 183, p. 131, 1914. 



