Adaptations of Fishes 191 



lens, the gland, the reflector, and the pigment. As to its func- 

 tion Prof. Greene observes: 



" I have kept specimens of Porichthys in aquaria at the Hop- 

 kins Seaside Laboratory, and have made numerous observations 

 on them with an effort to secure ocular proof of the phospho- 

 rescence of the living active fish. The fish was observed in 

 the dark when quiet and when violently excited, but, with a 

 single exception, only negative results were obtained. Once 

 a phosphorescent glow of scarcely perceptible intensity was 

 observed when the fish was pressed against the side of the 

 aquarium. Then, this is a shore fish and quite common, and 

 one might suppose that so striking a phenomenon as it would 

 present if these organs were phosphorescent in a small degree 

 would be observed by ichthyologists in the field, or by fisher- 

 men, but diligent inquiry reveals no such evidence. 



" Notwithstanding the fact that Porichthys has been observed 

 to voluntarily exhibit only the trace of phosphorescence men- 

 tioned above, still the organs which it possesses in such num- 

 bers are beyond doubt true phosphorescent organs, as the fol- 

 lowing observations will demonstrate. A live fish put into an 

 aquarium of sea-water made alkaline with ammonia water ex- 

 hibited a most brilliant glow along the location of the well- 

 developed organs. Not only did the lines of organs shine 

 forth, but the individual organs themselves were distinguish- 

 able. The glow appeared after about five minutes, remained 

 prominent for a few minutes, and then for twenty minutes 

 gradually became weaker until it was scarcely perceptible. 

 Rubbing the hand over the organs was followed always by a 

 distinct increase in the phosphorescence. Pieces of the fish 

 containing the organs taken five and six hours after the death 

 of the animal became luminous upon treatment with ammonia 

 water. 



" Electrical stimulation of the live fish was also tried with 

 good success. The interrupted current from an induction coil 

 was used, one electrode being fixed on the head over the brain 

 or on the exposed spinal cord near the brain, and the other 

 moved around on different parts of the body. No results fol- 

 lowed relatively weak stimulation of the fish, although such 

 currents produced violent contractions of the muscular system 



