Y. HANEDA 369 



with a long duct which connects with the luminous gland. The lumi- 

 nous gland of Acropoma Jianedai is very long compared with that of 

 Acropoma japonicum, and the muscles which form the lenses are 

 comparatively poor. I obtained pure cultures of luminous bacteria 

 from both species of Acropoma and found their general biological 

 characteristics quite different. 



Other luminous fishes of the same general type as Acropoma belong 

 to the Leiognathidae. These are true shallow-water forms and are 

 abundant in southern Japanese waters and in tropical seas. In 1937 

 at Palao I observed that Gazza minufa and several other species of 

 this family are luminescent when alive. Externally this fish does not 

 present any unusual features. It was only by careful observation of 

 the living fish by night that the luminosity of the lower half of the 

 body was revealed. 



The source of the luminosity is a swollen ring of gland which en- 

 circles the esophagus. The body cavity and the thoracic and ventral 

 muscles are so modified as to increase the efficiency of the light- 

 producing mechanism. The light is visible externally as a diffused 

 greenish blue light, sometimes intermittent. The light control mech- 

 anism is due to chromatophores which are scattered over the trans- 

 parent membrane that covers the luminous gland. These fishes have 

 a far more complex luminous organ than Acropoma. In Japan there 

 are three species, L. argentum, L. rivulatum, and L. elongatum, 

 which are usually dried for sale for food. In more tropical countries 

 there are many species of Leiognathidae. I obtained and observed 

 eleven species of Leiognathidae, distributed in three genera {Leio- 

 gnathus, Secutor, and Gazza) in the southwestern Pacific. 



Gazza occurs in clear water in Palao at depths of about 30 meters, 

 while Leiognathiis lives in turbid water in the mangrove zone at 

 depths of 1 to 2 meters. In Palao, L. eqinihis ranged in length up to 

 70 mm, while in Sandakan Bay, North Borneo, it was 200 mm long. 

 In Sandakan, Chinese fishermen catch these fish in nets and bring 

 them for sale to the Sandakan fish market. 



Around Singapore and the Malay Peninsula these fish are easily 

 obtained in all seasons from fishing traps known as "Kelong." In 1938 

 Fowler reported twelve species of this family in Malaya. In Java I 

 collected many species of this family in the fish markets of Jakarta. 



