138 PRODUCTS OP VITAL ACTIVITY. 



watch in a perfectly dark room, and such cultures have even been 

 photographed by their own light. 



The phosphorescence is influenced by changes in the culture 

 medium and by conditions of temperature, but we have no exact 

 knowledge of the mode of its production. The Bacillus phosphores- 

 cens from sea water in the vicinity of the West Indies gives the 

 most striking results, especially when planted upon the surface of 

 cooked fish and placed in an incubating oven at 30 C. Two other 

 species have been studied by Fischer one obtained from the water 

 of the harbor at Kiel, and the other a widely distributed species 

 called by Fischer Bacterium phosphorescens. Katz (1891) has re- 

 cently described several new species obtained by him from sea water 

 and from phosphorescent fish in the markets at Sydney, New South 

 Wales Bacillus smaragdino- phosphorescens, Bacillus argenteo-phos- 

 phorescens, Bacillus cyaneo-phosphorescens, Bacillus argenteo-phos- 

 phorescens liquefaciens (Nos. 337, 338, 341, and 342). 



