Although a positive response was obvious to the observer ^ 

 it was extremely difficult to measure quantitatively because of its 

 complexity and also at times because of erratic behaviour of the fish„ 

 Two quantitative measures were used, namely (1) the time out of 2- 

 (tank) or 3« (pond) minute periods spent by the fish in an "attraction" 

 area in which the test substance was dispersed, and (2) the number 

 of "passes" (movements of each fish in one of two directions) in the 

 attraction areao These measurements were usually made during five 

 control periods (before introducing a substance) and during five test 

 periods (after introducing a substance),, A roughly quantitative 

 (observational) measure of the strength of a response in one of five 

 categories (- to XXXX) was also recorded for each experiment^ With 

 either measure, the response to the sanne test substance was ex = 

 tremely variable in both manifestation and strength, producing appar- 

 ently inconsistent results in many of the replicated experinnentSo 



It is postulated that in tuna flesh there is present a 

 substance (or substances), herein called the attractant, which is 

 perceived by the tunny through its sense of smell or taste and which 

 promotes the urge to feed. 



The attractant was present in the flesh, viscera^, and 

 blood of several species of tuna and also in the flesh and blood of 

 certain white-fleshed fish. It was not present in beef bloodo It was 

 found in tuna cannery byproducts such as viscera preparations, 

 stickwater, and fish mealo 



Some 40 chemical compounds were tested as time 

 permitted, including certain amino acids, vitamins, aromatics, 

 proteins, etc„ In some, notably certain amino acids, vitannins, and 

 aromatics, there appeared to be a sensing of the dissolved or sus- 

 pended compound but the results could not be duplicated. In no case 

 did the response include all ol the components of a typical reaction to 

 a tuna flesh extracts 



Nature of the Attractive Substance 



Much of the work was devoted to attempts at 

 purification, fractionation, and identification of the unknown attract- 

 ant. Its properties are summarized in the paragraph which follows; 



The attractive substance is soluble in water and alcohol 

 but not in petroleum ether or acetone. It is not destroyed by cold or 

 by heat (although it may be partly precipitated on boiling an extract 

 which contains it)„ It is not precipitated by sodium chloride, tannic 

 acid, lead acetate, phosphotungstic acid, or other substances which 



58 



