352 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1911. 



McDermott ( 50 ) has recently recorded the results of some experi- 

 ments with liquid air, which show that exposure of the photogenic 

 tissue, fresh or desiccated, to this temperature, and grinding while so 

 exposed does not in the least affect the ability of the substance to 

 produce light upon restoration to the normal temperature. Macf ad- 

 yen ( 44 ) found that, while exposure of the luminous bacteria to the 

 temperature of liquid air did not inhibit their ability to produce 

 growth and light upon return to the normal conditions, trituration 

 at this temperature permanently destroyed the photogenicity. It 

 would appear, then, that there is some essential difference between 

 the microorganism and the insect in this regard. 



The photogenic bacteria present many interesting problems; their 

 ability to grow and luminesce in a medium consisting only of a solu- 

 tion of 3 per cent of sodium chloride and 1 per cent of asparagin in 

 water; the dependence of the marine species on the presence of certain 

 mineral salts, and these in certain concentrations, and upon the pres- 

 ence of oxygen, for light production; the pathogenic and symbiotic 

 relations existing between some species of these photobacteria and 

 some higher organisms are all matters of great interest. McDer- 

 mott ( 49 ) made some experiments with the view of determining any 

 chemical resemblances that might exist between these bacteria and 

 the fireflies. The work was on the whole inconclusive, but indicated 

 that if proper conditions could be arranged liquid cultures of the 

 bacteria might be dried and afterwards caused to produce light on 

 moistening. Molisch ( 52a ) found that the thicker layers of growth of 

 photobacteria on solid media could be dried and would exhibit their 

 photogenic activity on moistening. 



The well-known work of Kadziszewski ( 60 ) has already been referred 

 to, and also the more recent researches of Trautz ( 67 ). Delepine ( 9 ) 

 has experimented with a large series of thiocarbonic esters and 

 related bodies, which appear to be "phosphorescent" as the result of 

 oxidation, a phenomenon to which this writer has given the name 

 "Oxyluminescence." Hernandez and Cerdan ( 28 ) have questioned 

 Delepine' s view of the nature of the "phosphorescence" in these 

 cases, and refer it to a form of triboluminescence. In any event, 

 work along this line has some bearing on the problems of biophoto- 

 genesis, and it seems not too much to expect that it may develop that 

 in organic chemistry there will be found to be "photophore" or 

 "photogen" groupings, just as we now have chromophore and fluoro- 

 phore groupings, fluorogens, etc. 



Various observers have found the urates and phosphates of ammo- 

 nium, sodium, potassium, and calcium in the luminous tissue and its 

 ash. Dubois at one time seems to have rejected the oxidation theory 

 and to have believed that the light was due to the spontaneous 

 crystallization of ammonium urate (crystallo luminescence). 



