Y. HANEDA 367 



bryozoan. He noted that the bryozoan colony emitted a bluish light 

 for a few seconds when stimulated. A pair of light organs are situated 

 on each anterolateral part of the ventral membranous area in each 

 zoecium. 



Pisces 



Luminous fishes, depending on their method of light production 

 and the type of luminous organs, are divided into three groups: (1) 

 fish associated with luminous bacteria, (2) fish with well-developed 

 luminous organs or simple luminous skin organs, ( 3 ) fish with indirect 

 emission luminous organs, that is, the luminous gland lies inside the 

 fish body and the light is reflected so as to pass through a translucent 

 area of muscles. 



Fish Associated with Lmninous Bacteria 



In Japan the first group of luminous fishes have been studied in 

 rather great numbers. In 1916 Dr. Harvey, during his stay in Japan, 

 saw the light organs of the knightfish Monocentris japonicus, and he 

 predicted that luminous bacteria would be found in the luminous 

 organs. Later Yo. K. Okada (1926) studied the morphology and his- 

 tology of the organs, and Yasaki (1928) cultivated luminous bacteria 

 from the organs and confirmed Dr. Harvey's prediction. This fish is 

 commonly found in shallow water along the coast of Japan. The fish 

 is a beautiful golden yellow in color. Its luminous organs consist of 

 two oval protuberances lying side by side at the tip of the lower jaw. 

 In a fish 12 cm long the light organ is 4 mm long and 3 mm wide. 



The fishes of the families Gadidae and Macrouridae possess lumi- 

 nous glands on their ventral surfaces. The Gadidae live in compara- 

 tively shallow water and may be caught close to the coast of Japan. 

 The Macrouridae are deep water fish and are always caught by 

 trawlers as they inhabit a region over 100 fathoms deep. They are 

 taken most abundantly during winter season along the Pacific coast 

 of Japanese waters. 



Kishitani (1930) examined the luminous duct of Physicuhis japoni- 

 cus of the Gadidae and discovered it was an open type of luminous 

 gland containing symbiotic luminous bacteria, Micrococcus physiculus 

 Kishitani. 



