16 



AKT. 15. — IT. OIISHIMA : SOME OBSERVATIONS 



External Features, 



AU the organs, except the kiminous scales or " Leucht- 

 schuppen " of Brauer, are brightly shiny owing to the presence 

 of a reflector. 



As variously sized specimens of M. wcUasei could be obtained, 

 I have measured the size of the luminous organs in relation to 

 entire length of the fish : 



The diameter was always measured on the third thoracic organ 

 across the pigment septum. 



The table shows that the organ grows faster and attain 

 complete development relatively earlier than the length of 

 body. 



Histoloffy, 



The constituent parts of the luminous organs of Myct- 

 ophidse are : 1) photogenic body, 2) investing connective tissue, 3) 

 gelatinous tissue, 4) peculiar membrane, 5) " schuppenartige 

 Lamella" or ''squama profonda," 6) layer of hexagonal irides- 

 cent elements, 7) reflector, 8) pigment layer, 9) lens, 10) nerves 

 and l)lood vessels. The parts 4-9 are however accessory parts 

 and may be wanting in some cases. 



