COACTION IN LAMP-COMMUNITIES 239 



C. Preys absent. 



As I have asserted the significance of the prey of the object fishes 

 so strongly that readers may feel a contradiction in the title of this 

 paragraph, there is a case lacking the prey of the object fishes in the 

 community. It must be understood, however, that the light is used in 

 previous cases to gather fishes in places where no fish is found in 

 swarms. In this case, however, the light is used to attract the fishes 

 in places where fishes are found in swarms. 



In Harima nada, a part of the Inland sea west of Awazi Is., the 

 shoals of Engraulis are easily recognized on winter nights by the glim- 

 mering light brought about on the sea-surface by swimming Engraulis. 

 Fishing boats pursue the shoals and go across them, when the lamps 

 are lighted. The fishes are scattered at first, but the shoals are soon 

 reformed and keep the circular movement around the light. In this 

 case, there is no influence of the lower ranks on the behavior of Engra- 

 ulis, although there are some cases when the larger fishes such as yellow 

 tails (Seriola qiiinqueradiata) appear and disperse the shoal formed 

 around the lamp. It is not certain whether these higher predators are 

 the fishes always swimming after the shoal before the lamp is lighted 

 or fishes assembled after the lamp is lighted; although the former sup- 

 position seems more reasonable than the latter from the observations of 

 Engraulis shoals in the day time. 



D. Preys and predators absent. 



At Ejima, about 10 miles SSW from Murotsu, Engraulis shoals rest 

 at night among the rocks near the coast. These fishes assemble to the 

 light when a light of relatively weak intensity moves slowly along the 

 coast. In this case, the fishes assemble to the light so rapidly that no 

 effect of preys can be considered. Also the influences of other fi.shes are 

 not admitted, because the carangid and mackerel swim away to the outer 

 sea and yellow tails can not approach near the coast. There are found 

 some half-beaks {Hyporhamphus sajori) and flat-fishes (Paralichthys 

 olivaccus) mixing in the Engraulis shoal caught among the fishes in this 

 region by the light, but they are all of the indifferent group and scarcely 

 have any influence upon the shoal of Engvaulis. 



After many types of social structures of lamp-communities have 

 been discussed, it may be concluded that the mechanism keeping the 

 fishes near the light is based on the two factors, light and food-relations, 

 though these two factors are unable to be treated separately. There 

 are some intermediate forms between the animals comprising prey ani- 

 mals and primary predators, whose behaviors near the lamp are pri- 

 marily regulated by light, and the animals comprising quaternary and 

 end predators, whose behaviors near the lamp are regulated by the 



