214 Papers from the Department of Marine Biology. 



All the above experiments, then, point to the conclusion that if the 

 cell is broken up while moist or if the dead cells stand in contact with 

 water for any length of time, even though no oxygen be present, never- 

 theless the photogenic substance undergoes decomposition, a con- 

 clusion in harmony with my work and that of McDermott on the 

 firefly. As we have seen, extraction of the dried firefly luminous 

 organs with oxygen-free solvents will give no phosphorescent solutions 

 on admitting oxygen, because of this instability of the photogen 

 (p. 196). On the other hand, the substances in Cypridina extract are 

 stable in oxygen-free water (see p. 176). 



In the normal living bacterial cell (or firefly cell) I assume the photo- 

 gen to decompose through oxidation with light-production. If the 

 living bacteria are kept in sea-water from which all oxygen has been 

 removed and they stop glowing, they will still glow strongly if oxygen 

 is readmitted, even after a period of 24 hours. It is therefore obvious 

 that the breaking-up of the photogen in absence of oxygen does not 

 occur in the intact bacteria, but only in those whose normal "structure" 

 has been destroyed by cytolysis. I am inclined to believe that the 

 surface layer of the cell is the ' 'structure" involved. 



PHOTOGENIN AND PHOTOPHELEIN. 



As we have just seen, the light of a mass of bacteria disappears almost 

 instantly if they are broken up by any of the usual cytolytic agents. 

 This result is no doubt due to the fact that they continually burn 

 their light-producing substances as soon as they manufacture them. 

 The substances are therefore present in very small quantity. For 

 this reason we might expect to fail in demonstrating the existence of 

 photogenin and photophelein, although we must remember that forms 

 like Cavernularia, which contain a large amount of luminous material, 

 also fail in showing the photogenin-photophelein reaction. 



Since it is practically impossible to grind the luminous bacteria in 

 sea-water and so prepare an extract of photogenin, we are forced to 

 prepare our extract by cytolyzing with distilled water and thus obtain 

 a dark solution containing swollen suspended bacteria. This fluid will 

 give no light, however, on adding a suspension of bacteria heated to 

 boiling. Thinking that bacterial photophelein as well as photogenin 

 might be destroyed by boiling temperature, I tried heating to lower 

 temperatures, 90, 80, 70, 60, and 50, for 2 minutes, but in no case 

 did light appear on mixing with photogenin. Neither did these solu- 

 tions give light on mixing with firefly photogenin, but we can obtain 

 light from a bacterial photophelein prepared in the following way: 

 by adding absolute alcohol to a dense mass of the bacteria, then remov- 

 ing the alcohol by centrifuging, and quickly drying by evaporation in 

 vacuo. The resultant powder gives no light with water, but does 

 cause firefly photogenin to phosphoresce very faintly. Similar material 



