ox LUMINOUS ORGANS OF FISHES. 15 



in the organ have yielded no positive results. Some doubtful 

 cases of tliem were indeed met with, but I could not decide 

 whether I really had a nerve or something else before me. 



lAiminescence. 



The fishes were observed in a small fishing boat off the 

 coast of Manadzuru, Sagami, on a moonless night. 



My observations differed from Mangold's in that no lumi- 

 nescence could be observed when the fish was simply put in 

 fresh- water. A continuous light was made visible only when 

 some drops of formalin were added to it. The yellowish green 

 light was very feeble, not strong enough to illuminate any 

 object held near by. 



It was " ein ruhiges, nicht flackerndes Licht " ; there 

 was no sudden appearance and disappearance of light, nor 

 any sudden change in intensity. When the organs were crnshed 

 between the fingers and their contents exposed to the air, the 

 mucous matter (the mass of photogenic gland-cells) attached 

 to the fingers was found to be equally luminous. 



As regards the anteorbital organ, no luminosity could be 

 seen from the exterior. 



In agreement with Mangold, no spontaneous luminescence 

 has been observed. 



III. Luminous Organs of Myctophidse. 



From among this group of fishes with peculiarly developed 

 luminous organs, I have examined Myctophum {Blyclophum) 

 spinosum (Steindachner), M. {31.) aßne (Lütken), 31. {31.) 

 laternatum Garman, 31. {Dlajohus) watasei (Jordan and Starks) 

 and 31. {D.) sj)lendidum Brauer. 



