688 GREENE. [Vol. XV. 



"phosphorescent cells" by which they may take part in the 

 process ascribed to them.' 



The action of the organs described by him may be explained 

 on other grounds, and entirely independent of the so-called 

 "ganglion cells" and of the "phosphorescent cells." 



Phosphorescence as applied to the production of light by a 

 living animal is, according to our present physiological-chemical 

 notions, a chemical action, aii oxidation process. The necessary 

 conditions for producing it are two — an oxidizable substance 

 that is luminous on oxidation, i.e., a photogenic substance on the 

 one hand, and the presence of free oxygen on the other. Every 

 phosphorescent organ must have a mechanism for producing 

 these two conditions ; all other factors are only secondary and 

 accessory. If the gland of a firefly can produce a substance 

 that is oxidizable and luminous on oxidation, as shown as far 

 back as 1828 by Faraday, and confirmed and extended recently 

 by Watase, it is conceivable, indeed probable, that phosphores- 

 cence in Scopelus and other deep-sea forms is produced in the 

 same direct way, that is, by direct oxidation of the secretion of 

 the gland found in each of at least ten of the twelve groups of 

 organs described by von Lendenfeld. Free oxygen may be 

 supplied directly from the blood in the capillaries distributed 

 to the gland which he describes. The possibility of the regula- 

 tion of the supply of blood carrying o.xygen is analogous to 

 what takes place in the firefly and is wholly adequate to account 

 for any "flashes of light " "at the will of the fish." 



In the phosphorescent organs of Porichthys, the only part 

 the function of which cannot be explained on physical grounds 

 is the group of cells called the gland. If the large granular 

 cells of this portion of the structure (PI. XXXVIII, Fig. 4, 

 and PI. XXXIXr Figs. 5-7) produce a secretion, as seems 

 probable from the character of the cells and their behavior 

 toward reagents, and this substance be oxidizable and luminous 



1 The cells which von Lendenfeld designates " phosphorescent cells " have as 

 their peculiar characteristic a large, oval, highly refracting body imbedded in the 

 protoplasm of the larger end of the clavate cells. These cells have nothing in 

 common with the structure of the cells of the firefly known to be phosphorescent 

 in nature. In fact, the true phosphorescent cells are more probably the " gland 

 cells " found in ten of the twelve classes of organs which he describes. 



