McDermott- -Observations on a Photogenic Micro-organism. 183 



the oxygen is somewhat similar to use made of it in the 

 luminous insects, except that the gas is taken by the cells directly 

 from the air to which the organism is exposed, whereas in the fire- 

 fly an intricate network of trachea' supply the air for the process. 

 But while the nature' of the light emitted by these organisms, 

 and some of their chemical properties suggests a general simi- 

 larity of the photogenic processes in the two forms, it is by no 

 means necessary to assume that it is identical. It may even 

 prove that in organic chemistry we may have photophore group- 

 ings, as we now have fluorophore groups and chromophore 

 groups, and that biologic oxidations producing very similar 

 luminous manifestations may actually involve very different 

 active substances. The fact that these organisms will luminesce 

 in a medium consisting of water containing three per cent of 

 salt and one per cent of asparagin — <*-amino-succin amidic 

 acid — 



HOOC.CH 2 .CHNH 2 .CONH,, 



suggests that the process may really be less complicated than 

 would at first seem. 



So far as I know, Ps. lucifera is not pathogenic for man. It 

 appears to lie very small, and in common with most photogenic 

 micro-organisms, it is rather delicate; it grows and luminesces 

 best at 18-22° C. ; 28 to 30° C. will kill the cultures. 



The whole subject of the photogenic bacteria has been pretty 

 thoroughly covered in Professor Molisch's book, Leuchtende 

 Pflanzen (Jena, 11)04), and a very exhaustive and interesting 

 review of the entire subject of biophotogenesis, — regretably in 

 German again, — has been published by Prof. Ernst Mangold of 

 Greifswald, under the title Die Produktion von Licht, as the 

 2nd half of the third volume of Hans Winterstein's Handbuch 

 der vergleichende Physiologie. (Jena, 1910.) 



I have to thank Mr. Wm. Lindgren, of the Hygienic Labor- 

 atory, for propagation of this organism from the culture sent 

 me, and for advice in handling the same. 



