20 AKT. 15. — H. OHSHIMA : SOME OBSERVATIONS 



normal in that the photophores, especially the anteorbitals, 

 showed a faint continuous luminescence. 



Instances of actually observed luminescence are given by 

 Günther, Guppy, Emery and Nissen. The first mentioned 

 two authors give precise accounts of the matter but had before 

 them half-dead fishes only. The accounts given by the last two 

 observers are unfortunately very brief, though they seem to have 

 had good material. At any rate, I am of the opinion that 

 statements to the effect that their fish was spontaneously luminous 

 were due either to the abnormal state of their material or to 

 insufficiency of observation. 



" The larger pearly bodies of the pectoral region " which 

 Guppy found in a Scopelus were, I suppose, luminous scales. 



IV. Summary. 



I have dealt in the present paper witli three forms of 

 luminous organs which show difierent degrees of development. 

 They are : 



(1) The organs in Selachians. No numerical definiteuess 

 exists here, the organs being diffusely scattered, minute, 

 epidermal swellings partly sunk in the cutis. The photogenic 

 body consists of a small number of conical photogenic cells 

 arranged radially into a hemispherical or semicylindrical mass. 

 The lens is unicellular. No unequivocal innervation has been 

 proved, whilst the blood supply is carried on by a sinus under- 

 lying the organ. The light produced from the organ is tranquil 

 and faint, probably controlled by special activity of pigment 

 cells. 



(2) The organs of the Sternoptychidse (in strict sense). 



