(which took the lead) and its reactions were slower than that of 

 the tunny school „ These differences in behavior make it difficult 

 to draw general conclusions as to the relative strength of the react- 

 ion in the two species o 



Tll[hen the fish schooled, only one member of the school was tiiuedo 

 ■When both yellcwfm and tunny were present j the timing tests were con- 

 ducted alternately on each species o 



Finally it ^3hould be mentioned that the tuna tended to favor the 

 shady side of the tank, eogo> the east wall during the hours before 

 noono Before this was realized, many "positive" results were erron- 

 eously recorded in morning experiraentSj with ohe substance siphoned in 

 at C (figo 2)0 To avoid this difficulty, most of the experiments were 

 conducted between 11 aomo and 12s 30 pomo, with t he substance siphoned 

 in at Ao 



RESULTS 



The results ar'e shown gr-aphically in figSo 3 to 13^ The upper 

 panels show variation m the time in seconds required for 10 passes 

 in either direction across the line AC (figo 2)o The ordinate scale 

 has been reversed in direction so that increase in height of the 

 plotted points indicates increase in cruising speed and/or decrease 

 in the size of the swimming circles, ioeo, perception of the stimuluSo 

 In the acco\mt which follows, the word "cruising speed" has been used 

 to cover the complex behavior pattern measured by the time of 10 pass- 

 es,, The lower panels of figures 3-13 show variation in the number of 

 passes across the line AB| an increase beyond 5 shows that the fish 

 describes one or more complete circles in the near (west) half of the 

 tank, ioeo, it indicates attraction to the point of stimulation;, 



io Baitfish water 



Five experiments were performed with similai' resuitSo Only one 

 yellowfin was presento The results of one experiment are recorded in 

 figure 3o 



During the preliminary timing^, the yellowfin' s cruising speed 

 gradually decreased to an approximately constant valueo When the 

 baitfish, or "conditioned," water was siphoned in at A> there was no 

 apparent change in either cruising speed cr in the number of passes 

 across AB- Similarly, when the baitfish water was siphoned in at C^ 

 there was no apparent change in cruising speed or in the number of 

 passes across CC The experiment does not demonstrate the false 

 "positive" attraction which may result from the tuna's preference for 

 the shady side of the tank, although it was shown in other preliminary 



12 



