No. 3.] PHOSPHORESCENT ORGANS. 6S9 



in the presence of free oxygen, i.e., photogenic, then we have 

 the conditions necessary for a light-producing organ. The 

 numerous capillaries distributed to the gland will supply free 

 oxygen sufficient to meet the needs of the case. Light pro- 

 duced in the gland is ultimately all projected to the exterior, 

 either directly from the luminous points in the gland or reflected 

 outward by the reflector, the lens condensing all the rays into 

 a definite pencil or slightly diverging cone. This explanation 

 of the light-producing process rests on the assumption of a 

 secretion product with certain specific characters. But com- 

 paring the organ with structures known to produce such a sub- 

 stance, i.e., the glands of the firefly or the photospheres of 

 Euphausia, it seems to me the assumption is not less certain 

 than the assumption that twelve structures resembling each 

 other in certain particulars have a common function to that 

 proved for one .only of the twelve. 



I am inclined to the belief that whatever regulation of the 

 action of the phosphorescent organ occurs is controlled by the 

 regulation of the supply of free oxygen by the blood stream 

 flowing through the organ ; but, however this may be, the 

 essential fact remains that the organs in Porichthys are true 

 phosphorescent organs. 



Stanford University, Cal., 

 August 13, 1S9S. 



