334 EUPERT VALLENTIN AND J. T. CUNNINGHAM. 



microscope and the head of the observer the green colour dis- 

 appeared, and nothing could be seen. It is evident then that 

 the inner surface of the reflector possesses in a marked degree 

 the property of fluorescence, and the appearance described is 

 due to this property, not to a pigment. When white light 

 falls upon the surface in question its more refrangible rays are 

 made less refrangible and given off as a greenish light, while 

 the purple colour seen by transmitted light is due to the 

 absorption of the blue and green rays, and the transmission of 

 the remainder. 



As stated above it appeared from the examination under the 

 microscope that the surface of the reflector gave off no light 

 under the conditions described, in perfect darkness. But we 

 afterwards fou.id that when a slide containing a crushed organ 

 was viewed by the naked eye in the dark there was always a 

 luminous spot in the preparation, which shone with an intrinsic 

 light, and on examination the luminous portion always proved 

 to be the reflector, whose inner surface gave off the light. It 

 is to be noted that the colour of the surface of the reflector 

 was seen equally well, whether the surface was viewed directly 

 or seen through the thickness of the reflector, for the latter 

 was transparent. 



It was stated above that when an animal was completely 

 crushed by rubbing between the hands certain particles in the 

 scattered tissues were continuously luminous in the dark. It 

 was easy to pick up one of these particles with the forceps, 

 place it on a slide and examine it with the microscope ; this 

 we did repeatedly, and always found that the particle was the 

 whole or a portion of a reflector, which was always purple by 

 transmitted light. 



It is evident that our results differ from those of Sars with 

 regard to this question of the light-producing part of the 

 organ. We found no evidence whatever that the central mass 

 of straight fibrils gave out light, and it never showed any 

 colour phenomena : it was always transparent and colourless. 



When the organs are examined in the living animal in day- 

 light, the interior of each is seen to have a yellow-green 



