BASIS OF ANIMAL PHOSPHORESCENCE. 115 



decomposition of the living substance of the cell ; but instead 

 of being thrown out of the body, like some other products of 

 secretion, they are consumed in situ by combining with oxygen 

 brought in from without. 



The fact that the granules themselves are dead is shown by 

 taking the luminous organ from the organism and crushing it 

 on the slide, thus depriving it of all traces of vitality ; yet the 

 light continues to come out, in fact it becomes more luminous 

 the greater the exposure to air. 



The mode by which each luminous cell is aerated by the 

 tracheal "capillaries" is of considerable interest. The "capil- 

 laries ' ' are the ultimate branches of the respiratory apparatus, 

 and start from the ultimate branches of the tracheal tube, some- 

 what in a similar manner as the tentacles do from the body of 

 a hydra. If one imagines these " capillaries " are spread around 

 the photogenic cell in the same manner as the hydra spreads its 

 tentacles around an organism much larger than itself, which it 

 has captured for food, he may get a fair idea of the relation of 

 the aerating apparatus to the light-producing cell. 



The size of the luminous cell being comparatively large, more 

 than one bunch of hydriform "capillaries" is found distributed 

 over the surface of each luminous cell. The substance of the 

 "capillaries" seems to have a remarkable affinity for oxygen, 

 and it is, no doubt, through this mechanism that the oxygen of 

 the inspired air is quickly separated, and just as quickly applied 

 for the combustion of the photogenic material in the periphery 

 of the cell. 



As to the chemical nature of this material little is known ; 

 but it is a secretion of fatty nature, which oxidizes readily in 

 alkaline media. Phosphorus has nothing to do with the 

 phenomenon. 



The animal has control of the production of light through 

 its respiratory mechanism, not directly upon the luminous 

 cell, although nerves may have indirect influence upon the 

 general metabolism of the cell. When more oxygen is sent 

 with the air, the illumination is greater ; when the air is with- 

 held, there is less light, or even a complete darkness, just as the 

 dull red coal may be ignited so as to emit a white light by a 



