linko The substances were dissolved m sea water immedia'ely before 

 testing to avoid hydrolysiSo The barium salt of adenylic diphosphate 

 was dissolved in 0„ 1 N hydrochloric acid and the barium was precipi- 

 tated with 6N sulphuric acid to have it present as free adenosine 

 diphosphate acidi, rather than as a barium salt (there had been indica = 

 tions that barium tended to destroy the attractive material^o I* was 

 presumed that the pH of seawater would assure the proper molecular 

 form of the sodium salt of adenosine triphosphateo First tests indica = 

 ted a sensing and an attraction of the tunny to both adenosine triphos* 

 phate (Noo 243) and diphosphate (Noo 2451 but not to adenosine (NOo 

 242) nor to adenylic acid (Noo 2445o However^ later tests with both 

 the triphosphate JNoSo 254 and 271) and the diphosphate (NoSo 255 and 

 270) gave negative resultSo 



The two dyeSj, eosin red (fNoo 36) and methylene blue 

 (Noo 38);, were visually repellent to the fisho This sanne reaction^ an 

 avoidance^ was occasionally noted with strong solutions of the green~ 

 ish fluorescein:, 



In addition to the substances listed above^ two alleged fish 

 attractants were tested^ one known as "Slik" which smelled of cod 

 liver oil;, and the other an unnanned "fish lure" which snnelled of tuna 

 or herring viscera extracto There was a slight sensing of the first 

 (Noo 174) and a weak but positive reaction to the second 'NOo 349)o 



ATTEMPTS AT TSOLATTON AND IDENTIFICATION 

 OF THE ATTRACTANT (S< 



The attractantCs) was initially segregated from the flesh 

 or other parts of the fish by virtue of its solubility in water,, ThuSj, on 

 centrifugingj the aqueous extract of finely-^divided tuna, flesh formed 

 a clear amber to reddish colored solution which usually caused a 

 strong positive response fNos, 1^ Sj, lOj, and numerous other experi= 

 ments in both tank and pond)o The residue from centrifuging was 

 either attractive fNOu 15) or not (NOo 2)^ depending on either the 

 thoroughness of the extraction or the part played by vision in the case 

 of the murky mixture o 



In early tank experimentSj boiling of tuna flesh with water, 

 thus precipitating the proteins and similar compounds^ appeared to 

 remove or destroy the attractanto The clear filtrate from the boiled 

 flesh failed to elici' a response 'NoSo 5^ 9^ 11„ 12t, 211 as was also found 

 previously by van Weel » 19521, However j, as will be discussed later^ 

 this was not the case with boiled extract of flesho 



DialysiS;, using a cellophane tube (K-S/S inch diameter),, 

 was next tried in an attempt to segregate the attractantp using clear 



37 



