MICROSYMBIOSIS 87 



bacteria with a leaf extract containing chlorophyl. Wlien 

 the mixture was kept in the dark for some time, the bacteria 

 showed no Imiiinosity, but if the mixture was then exposed 

 to sunlight for only a minute the bacteria became luminous. 

 The light from a burning match was sufficient to restore the 

 luminosity of the organisms after they had been kept in 

 the dark for some time. By means of these experiments it 

 was possible to detect very minute quantities of oxygen 

 liberated by the chlorophyl. Molisch utiUzed the luminif- 

 erous bacteria to test for the complete absence of oxygen 

 in anaerobic culture media. Very small amounts of oxygen 

 in the media were sufficient to produce luminosity in the 

 bacteria. 



In the beetles, whose luminosity appears to be inter- 

 mittent, Dubois, Verworn and others, have observed that 

 the Ught does not entirely disappear between "flashes." 

 Dubois experimented extensively with these beetles, and 

 found that when he checked the flow of blood by bending 

 the prothorax, the ''flashes" did not occur. When he 

 pressed on the abdomen and forced the blood along more 

 rapidly, the "flashes" coincided with each compression. 

 The tracheal tubes, apparently, also bring oxygen to the 

 cells containing the luminiferous bacteria. The nature 

 of the mechanism, that is responsible for the "flashes" in 

 insects is not definitely known. 



Luminosity in the tunicate, Pyrosoma, was observed 

 centuries ago. Buchner, recently, has investigated these 

 forms, and has traced particularly the luminiferous sym- 

 bionts in the more or less comphcated development of the 

 host. Various interpretations have been given by different 

 authors regarding the nature of the luminosity. Buchner 

 has demonstrated cells that contain the fight-producing 

 microorganisms which are comparable to the myceto- 

 cytes. He befieves that the microorganisms are fungi, 

 although he thinks it is quite possible that they are "bac- 



