Adaptations of Fishes 63 
lens, the gland, the reflector, and the pigment. As to its func- 
tion Prof. Greene observes: 
“T 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 Porichtlhys 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 
