COACTION IN LAMP-COMMUNITIES 237 



relations can be expected also in the benthonic fishes, although they can 

 not be ascertained easily. 



It the above-mentioned relations are correct and of important eco- 

 logical significance, there must be a lot of phenomena reflecting these 

 relations distinctly. The social structure of the lamp community and 

 the arrival order of various animals near the lamp may be accepted as 

 good examples of these phenomena. 



When the lamp is lighted, many animals assemble one after an- 

 other and after a certain time they attain a condition of equilibrium. 

 At this time the animals occupy their situations horizontally, perhaps 

 also vertically, from the nearest part of the lamp to the periphery ac- 

 cording to the folloMdng orders (several actual examples are given be- 

 low): — planktonic crustaceans — Engraulis of Shirasu stage — Engraulis 

 of grown stages — Carangidae — Sphyraena (22h. 25 min. June 23, 1950), 

 planktonic crustaceans — Engraulis of Shirasu stage — Pempheris — Ca- 

 rangidae — squids — (111. 00 min. Aug. 6, 1950), planktonic crustaceans — 

 Stolephorus — Engraulis of grown stages — Pempheris — Carangidae — 

 Sphyraena (2h. 40 min, Aug. 6, 1950), planktonic crustaceans — Engrau- 

 lis of Shirasu stage — Stolephorus — Engraulis of grown stages — Sphy- 

 raena (19h. 45 min. Aug. 11, 1950). The arrangement of the situation of 

 the animals from the nearest part of the lamp to the periphery is quite 

 parallel to the order mentioned previously. This arrangement is called 

 the standard form, from which many modifications are derived by the 

 dispersive activity of the higher predators. When higher predators 

 are not so numerous or their predating activities are not so violent, 

 the spatial relations of lamp-animals are not changed, except for the 

 animals of the lowest rank of the community, which are unable to keep 

 their positions and are driven away from the central part \Stolephorus 

 — Carangidae — Sphyraena — benthonic fishes (vertically) or squids (ho- 

 rizontally) (4h. 05 min. June 24, 1950), Engraulis of grown stage — Stole- 

 phorus — benthonic fishes (vertically) or squids (horizontally) (4h. 10 

 min. Aug. 17, 1950), Stolephorus — Pempheris — Carangidae— benthonic 

 fishes (vertically) or squids (horizontally) (Oh. 00 min. Aug. 6, 1950), 

 Carangidae — Sphyraena (vertically) or squids (horizontally) (23h. 05 

 min. Aug. 22, 1950)]. When the higher predators are numerous their 

 predating activities become more violent, the spatial relations of ani- 

 mals in the community are reversed; the central part is occupied by 

 animals of higher ranks[r)'/o5Mrw.y — Carangidae — Pempheris — Engra- 

 ulis — squids (2h. 40 min. Aug. 23, 1950) and T)'/o5MrM5 — Carangidae — 

 Stolephorus (2h. 00 min. Aug. 24, 1950)] . Lastly comes the case when the 

 predating is very violent. This time most animals are unable to ap- 

 proach the light, the community consists merely of the predators and 



