PHOTOSPHERIA OF NYCTIPHANES NORVEGICA. 323 



close to the eyes are first and most brilliantly illuminated, and 

 then the light, which is bluish white, spreads to the other 

 organs on the trunk and tail. After a brilliant flash has been 

 emitted from the organs they glow for some time with a dull 

 light. The light is given out at will by the animal, and usually, 

 but not always, when irritated. Subsequent flashes become 

 less and less bright till the animal appears to lose the power 

 of emitting light. If the organs be removed with the forceps 

 the points will glow brightly for some time, and when the 

 animal is dying the whole body is frequently illuminated by a 

 diffused light. These phosphorescent organs appear under the 

 microscope as pale red spots, with a central, clear, lenticular 

 body. The phosphorescent light comes from the red pigment 

 surrounding the lenticular space. 



"In August, 1880, Mr. Murray observed at night on the 

 surface of the sea in the Faroe Channel, large patches and 

 long streaks of apparently milky-white water. The tow-nets 

 caught in these immense numbers of Nyctiphanes (Thysa- 

 nopoda) norvegica, M. Sars, and the peculiar appearance 

 of the water seemed to be due to the diffused light emitted 

 from the phosphorescent organs of this species.'" 



Professor G. C. Sars mentions the light producing function 

 of the organs in his " Preliminary Notices of the Schizopoda 

 of the ' Challenger/ " published in 1883, 1 and in his "Report on 

 the Schizopoda " (1885), he discusses at some length their struc- 

 ture and function in his account of the genus Euphausia. He 

 believes, after careful examination of the structures both in 

 spirit specimens and in the living animal, that they are highly 

 differentiated luminous organs. It is unnecessary to repeat 

 his description of the position of the organs, it confirms that 

 already quoted from Claus, with the addition of the pair of 

 organs situated in the eye peduncles and mentioned in the 

 "Challenger" narrative. He says the organs are globular 

 bodies with a very complicated structure, bearing in some par- 

 ticulars great resemblance to that of the eyes in Vertebrates. 

 A rather thick and elastic cuticle forms the outer envelope of 

 1 Christiania Videns. Selsk. Forh., 1883. 



