8 ART. lö. TT. OHSHIMA : SOME OBSEKVATIONS 



peduiiCLilnr part remained dark. On the dorsal side of the fish 

 I have not been able to observe any luminescence. 



The light wds quite tranquil and not flaring, and it must 

 be stated in particular that spontaneous luminescence has never 

 been observed. 



When the fish was held in one hand and was pressed or 

 rubbed with the other, the luminescence was not immediately 

 called forth but became apparent after some minutes, the light 

 gradually appearing or vanishing or attaining maximum intensity 

 here and there at different places. 



Stimulation with ammonia water did not show any effect on 

 luminescence. 



Previous accounts of the luminescence of Selachians, but espe- 

 cially those of Bennett for Isistms hrasiliensis and of Beer for Spi- 

 naxniger, agree well with my results as regards the topography 

 of lightproducing areas and the parts where the light was most 

 intense. But Beer's statement that he observed no change of lu- 

 minosity on application of diverse mechanical stimuli does not agree 

 with my observations. The reason lies perhaps in the fact that 

 he experimented on a severely wounded specimen. It seems to 

 me too great an exaggeration to say, as Burckhardt did, that 

 the phenomena might be observed even in day-light. In fact, 

 the intensity is far from being strong, so that one can not 

 recognize the light in a dark room unless the eyes were pre- 

 viously brought into adaptation with the darkness. 



The facts that no sudden change of luminosity takes place and 

 that there is such a local difference in the intensity of the emit- 

 ted light may, in some cases, be due to the action of the pigment 



