It was observed in thisj, as in many other experiments^ that 

 before the substance was introduced^ the two species formed one 

 compact schoolj, with the yellowfin trailing, but when an attract- 

 ive substance was introduced, and the fish became excited^ each 

 species reacted at different cruising speeds^ thus breaking up the 

 compact school formationo 



In a second experiment,, one yellowfin and two tunny were pres- 

 ent, the yellowfin leading the school « The whole preparation of 

 yellowfin flesh (150 grams ^ yielding 300 cubic centimeters of ^^hole 

 extract) was divided into the fcllowing quantities^ each of which 

 was diluted to 3 liters with seawaters (1) Sg (2) 10 j (3) 50, and 

 CU) 23$ cubic centimeters „ Three of the tunny had &ed and the 

 remaining two seemed listless when this experiment, waa performedo 

 Consequently J, strong reactions were not expectedo The results 

 were similar to those of the previous experiment although the 

 reactions were not as pronounced o There was an indication that 

 ths tunny sensed the most dilute (1) solution in that they often 

 hesitated at the inlet but then quickly increased their speed so 

 that they caught up with the yellowfin,, Both the tunny and the 

 yellowfin made more passes across AB than BC^ indicating attract- 

 ion,, With (2) J the stimulus was apparently strong enough to cause 

 the tunny tc leave the yellowfin and react independently o Again j 

 an increase in cruising time and number of passes for both species 

 indicated attraction. With (3), the tunny frequently remained near 

 the inletj and orOy occasionally joined the cruising yellowfino 

 Again attraction was indicated in both species. With (k) both 

 yellowfin and tunny showed a pronounced increase in cruising speed 

 and in number of passes across AC However the fish did not mill 

 around the inlet as in the previous experiment^ even when the re- 

 mainder of the whole preparation was poured into the tanko 



Fo The objection might be raised that attraction to the txma 

 flesh prepai'ation occurs because the t-una were conditioned to this 

 kind of foodj and that a similar reaction would not necessarily be 

 obtained with "wild" fisho This possibility cannot be denied^ al- 

 though it is shown in the experiment to follow that the reaction 

 was also obtained with marlin flesh. The only survivor^ the yellow- 

 fin, had not yet been fed this material so it coul.d not have been 

 conditioned to ito 



Unfortunately, the yellowfin was in goor condition and did not 

 show pronounced reactions to its food. Accordingly it was considered 

 that even a weak reaction would be evidence of an attractive sub- 

 stance. Several experiments were performed vvith similar results o 

 Only one is recorded in figure 13 in which 260 grams of marlin flesh 

 was used as a whole preparation. 



28 



