ON LUMINOUS ORGANS OF FISHES. 19 



quently found to be very imperfectly developed in the specimens 

 I had examined in life. The branchiostegals, the operculars and 

 all other " schüsseiförmige " organs shine more feebly than the 

 anteorbitals and the luminous scales. 



The light omitted is of a pretty blue colour, but its power 

 of illumination is so weak that in 31. watasei, with all the 

 photophores in action, I never could recognize even big prints 

 on a paper held almost in contact with the fish, though care 

 was taken previously to entirely adapt my eyes to darkness. 



The light was a momentary one just like an electric spark, 

 quite different from those of 3Iaurolicus and Etmopterns. 



No spontaneous gleaming was observed. 



In fresh-water and in a dilute solution of formalin the fish 

 remained dark. 



Mechanical stimuli were effective in bringing the organ 

 into action, as when the fish was pressed between the fingers, or 

 when the brain was cut out. The latter operation was always 

 followed by emission of light of maximum intensity from the 

 anteorbitals and the luminous scales. 



By the mode of action one can distinguish two groups of 

 the organs, the anteorbitals and the luminous scales (and probably 

 also the mediocaudals) on the one hand, and all the other small 

 organs on the other. The two groups act quite independently 

 of each other, while within each all the photophores become 

 simultaneously active. A weak stimulation was followed by the 

 emission of light only from the second group, while the first 

 group could be forced to action only by a stronger stimulation. 



Once some dying fishes brought ashore in a basket fell into 

 my hands. Subjecting them under observation, I have found 

 that their luminous phenomena differed markedly from the 



