236 EIGHTH PACIFIC SCIENCE CONGRESS 



rarer than the first, while those near the bottom are represented by 

 Epinepherus and its allies. 



(5) Indifferent group: This group consists of the fishes which 

 have no significant relation to other animals on account of their 

 meagre population, short staying time under the light, and the fact 

 that they seldom eat or are eaten near the lamp. Some members of 

 this group occupy the situation between the lamp fishes and those 

 not assembling around the light; some others show enormously strong 

 phototaxis. Crabs, Atherina, Cypserulus, Miigil, Euthynnus, Tylosu- 

 rus, Teuthis and Ostracion are the main members of this group. The 

 following four inclinations are deducible from the above-mentioned 

 classification. 



1. The size of a lower rank is, in general, smaller than that of 

 the higher rank. The fishes of the younger stage belong to a rank 

 lower than that of its full-grown stage. 



2. The fishes of the lower rank take the food lower than that of 

 the higher fishes. 



3. The fishes of the lower food rank are controlled more strongly 

 by the light. 



4. The fish with a stronger dispersing influence on the community 

 is placed in the higher rank. 



Generalizing these inclinations, we may be able to determine the 

 niches of main lamp-animals as follows: (small planktons can not be 

 assembled by the light in the streaming tide) — smaller planktonic crus- 

 taceans [Oncaea venusta and Calanus) — larger planktonic crustaceans 

 (megalopae, Gammalid amphipods and Siriella) — Engraulis of Shirasu 

 stage — Stolephorus — Engraulis — (Clupeidae) — Pempheris — Carangi- 

 dae — Sphyraena — squids — Trichiurus — Squalus Coryphaena — Dol- 

 phinus. 



The lamp animals and those not assembling around the light can 

 not be separated distinctly from each other, but they are connected 

 completely by the existence of many fishes showing various degrees of 

 tendencies to assembling around the light. The distance between these 

 intermediate fishes and the lamp-animals may be determined by the 

 stability of the shoal, coaction to other animals and other behaviors 

 of the former. Thus, the primary predators assembling around the 

 light and the fishes of the same rank not assembling near the lamp are 

 continued which each other by a series of the following intermediate 

 fishes — Atherina — Cypserulus — Mugil — ; in the secondary predators 

 the series is represented as — mackerel — Sarda — Eiithynnus — {Kat- 

 mivonus) — ; and in the tertiary predators it is - Tylosurus — . Similar 



