western 1/lOth of the pond. On turning back they sped eastward 

 through the field in 12 seconds (seventh histogram,, The two tunny 

 which separated from the school earlier circled slowly outside the 

 eastern border of the fieldp and 15 seconds after the nriajor school 

 left these two fish re-^entered the area and swam inside for 18 

 seconds (eighth histogram)o 



When a pair of colored lures was lowered repeatedly 

 into the water inside the attraction area^ one or more tunny might 

 be moving westerly towards the ^rea and near enough to see the 

 moving objects. In this case they would usually swim toward the 

 lures and try to take thema It often happened that when one or two 

 tunny started to bite^ the others near them would become active and 

 circle back to the lureSo On the other hadj, if the tunny were at the 

 far end of the pond„ the lures might be lowered repeatedly for a 

 long time without any response from the fish until they approached 

 the attraction areau When taking after the lureSj, the speed of move* 

 nnent was not noticeably increased compared with that during the 

 control periods 



Figure 19B shows the reaction of the tunny in an experi- 

 ment in which two lures, one red and the other blacky were presented„ 

 They entered the field 17 times in groups of different sizes^ In the 

 third 3-minute interval,, attraction and excitement is indicated by the 

 close spacing of the histograms. The symbols "C" and "O" in the fig- 

 ure- ir.dic ate looping andcirclingp respectively^ inside the area, Fronn 

 the strokes indicating the response to the lures (upper line), it will 

 be seen that they attennpted to "take" the red lure 8 times and the 

 black lure 6 timeSo 



When a stock extract of tuna flesh was introduced 

 through the stream of water at the western end of the pond the tun-" 

 ny would become greatly excited as soon as they sensed itj Usually 

 the extract was propelled Into the attraction area about 1 minute 

 after its introductiono The fish would dash about with increased 

 speedp biting at floating objects such as leaves and sticks, as well 

 as running for the lures and fighting among themselveSo There was 

 a clearly visible feeding reactiono But after 10 to 15 minutes the 

 response would gradually disappear and they would assume a pattern 

 sinnilar to that seen when lures alone were used,^ 



In figure 19C a kymograph record of the response to 

 lures and extract is seen. The number of passes at the lures is 

 indicated by numbers rather than by strokes. The great excitement 

 when extract was added is evident from the increased frequency of 

 the histograms,, together with their varied shapeo The fish took the 



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