230 EIGHTH PACIFIC SCIENCE CONGRESS 



above each of them. In order to make the illumination for the colored 

 lights equal to 50 lux on every water surface of the eight compartments, 

 some sheets of white paper were piled up over these filters for adjusting 

 the light. The color filters were arranged in two ways, one in the order 

 of wave length and the other at random in order that the fish might 

 not become familiar with the color arrangements. 



We observed the rates of frequencies of the time of entrance of 

 the fishes into each compartment of various lights, and compared the 

 rates with the relative energies which were calculated by the transpar- 

 encies of the filters, sensibilities of selen photometer and radiant ener- 

 gies of the lamp, and judged their phototaxis tendencies. By this meth- 

 od, we got considerable experimental results and will show the ab- 

 stract of these as follows: 



One of my co-workers, Dr. Osaki, studied the relation between the 

 phototaxis and the aggregation of young marine fishes, because, in a 

 biological phenomenon, the aggregation frequently comes into ques- 

 tion. Some investigators who have studied on the fish aggregation, have 

 probably made the assumption that apparent gatherings are real ag- 

 gregations. Nevertheless, it is possible that two fishes actually form an 

 aggregation even when they are so apart from each other that they may 

 be considered as a group. Therefore, it is next to impossible to con- 

 clude from the appearance whether a gathering is an aggregation or not. 

 In our studies on the phototaxis of fish, it is necessary to conduct re- 

 search on how aggregation affects the phenomenon and what difference 

 exists between the phototaxis of the individual fish and that of the ag- 

 gregated fish. The shape of the curves of fish gathering rate varied in 

 accordance with the number of fishes employed and wave lengths in the 

 experiments, but, at any rate, fishes are constantly forming various types 

 of aggregation, the shapes of gathering rates of each individual were at 

 random, while those of two or more numbers of fish in an aquarium 

 coincided with each other and maximum values of these appeared at 

 the range of green and blue colors in common fishes (Dr. H. Ozaki). 



The types of phototaxis of fish were found to be divided into two. 

 One was the greatest fish-gathering rates in the range of wave lengths 

 of green and blue as were seen in Oplegnathus, Monacanthus, Cybium, 

 Spheroides and Sphyraena, while the other was quite contrary as in 

 Anguilla (M. Takeda). 



The product of radiant energy of light of certain wave length and 

 the visibility of eyes to that light was called "Spectral luminosity" for 

 the same wave length; and when the spectral luminosity was calculated 

 by using the human visibility curve with the maximum displaced suit- 

 ably as a substitute for the true visibility curve of eyes of fish, it turned 



