no reactiorij, but then the fish swam rapidly in small circles 

 around the inlet „ Ihe reaction j particularly of the tunny, was 

 clearly positive, although not as violent as iivith the normal 

 clear extract o Tlie yellowfin behaved similarly to the tunny j 

 but might have been influenced by their behavior. None of the 

 fish snapped at the xnleto After normal cruising of the tank was 

 resumed, the fat fraction was introduced;, Ihere was no detectable 

 reactions 



A second experiment illustrates the behavior somewhat better j, 

 as the reaction was somewhat less pronounced and the timing tests 

 could be continued throughouto In this<, yellowfin flesh (180 grams) 

 was again used_, yielding 225 cubic centimeters of the clear solution 

 which was shaken with $0 cubic centimeters of petrol ethero Both 

 species schooled together^ mth the yellowfin trailing. The results 

 are shown in figures 9 and 10 o As soon as the protein fraction was 

 introduced, the fish were attracted and cruised in small circles at 

 the inlet o The yellowfin "sniffed" at the tube during Tests l5 and 

 19s ^^^ "the tunny both "sniffed" and snapped at the inlet during 

 Test 18 After waiting 2$ minutes, the fat fraction was siphoned 

 ino Unfortunately when siphoning was started^, two onlookers 

 appeared whose presence attracted and excited the fish (Tests 33 to 

 14.0)0 Ullhen they went away^ the normal cruising speed of the fish was 

 resumedo Except for the disturbing presence of the onlookers^ the 

 results are similar tc those m the previous experimento It appears 

 that the attractivB substance is located in the protein rather than 

 the fat fraction of the clear extract of tuna fLesho 



Eo A series of experiments was next performed to determine the 

 extent to which the tuna flesh preparation could be diluted and still 

 retain its quality of attractiono In these the whole preparation was 

 used J but it was made up in various dilutions o It should be kept in 

 mind that the concentrations given are those siphoned into the tank^ 

 and not those in the tanko "he concentration in the tank would be 

 difficult to determine as it does not remain constant because of 

 diffusion,, 



In the first experiments one yellowfin and five tunny were 

 present schooling togethero The whole preparation of yellowfin flesh 

 (156 grams ^ yielding 300 cubic centimeters of whole extract) was 

 divided into the following quantities and each was diluted to 3 liters 

 with seawaters (l) 10;, (2) 50-, (3) 90o and (ii) 150 cubic centimeterso 

 The results are shown in figures 11 and 12 When (1) was siphoned in, 

 there was an increase in cruising speed but no definite attraction to 

 the inlet o When (2) was siphoned in, there appeared to be a definite 

 attraction as both the yellowfin and tunny swam in small circles near 

 the inlet during the siphoning processo TShen (3) was siphoned in, 

 the reaction was similar, but for some unknown reason it was less 

 pronounced than in (2)o lilfhen (h) was siphoned in^ the reaction soon 

 became very pronounced., both species milling around near the inlet 

 at high speed for about 5 minutes » 



23 



