Y. HANEDA 



353 



sists of many groups of luminous cells which run parallel to each 

 other. No luminous cells are scattered over the whole body. 



When the dried materials of both species were ground in a mortar 

 and moistened with water, luminescence reappeared and then disap- 

 peared. The luciferin-luciferase reaction, tested by mixing hot water 

 (70° C) and cold water extracts of crushed Planoxis, was negative. 

 When the cold water extract is allowed to stand until the light disap- 

 pears, it will not again emit light when ATP is added. 



Fig. 5. A Planaxis viratus removed from its shell to show the luminous organ 

 in diagram at right. 



Cephalopoda 



There are many reports of luminous squid in Japan. According to 

 Harvey (1952) luminous squid are divided into the following three 

 groups, depending on their method of Hght production: (1) squid 

 associated with luminous bacteria, (2) squid producing an abundant 

 luminous secretion, and (3) squid with well-developed photophores 

 and intracellular luminescence. In Japan the first and third groups 

 have been studied by such workers as Watase (1905), Ishikawa 



