remove proteins and purineso It will pass through a dialyzing 



membrane (in partj, at leastJo It is not adsorbed fto any l&rge extent) 

 on activated caybono It may be loosely adsorbed on colunnns oi ac- 

 tivated Alumina or ion exchange resuiSo Of the la^tterp it appeiirs to 

 be held to a greater extent on an cinion exchanger thjtn on a cation 

 exchanger^ although the results are not consistento It is affected 

 slighrlyp if at all^ by radical changes in hydrogen ion concentration^ 

 In its purest form yet att.ainedj chemical teste showed the presence 

 of phosphorus (but not sulphur% the amide linltp and the benzene ringo 



It is not ye*: possible to identity the attractive 8ubstance(8) 

 from its chemical properties o it does not appear to be an amino acid, 

 a fatty acid or lipoidj a pur-ne^ or a protemo In many of its proper- 

 ties it resembles Vitamin Bi^o but this substance^ while sensed by 

 the fisht, did not promote a typical positive response when testedo 



Preservation of the At tractant 



As sea testing of the extracts was contemplatedu 

 considerable interest centered on methods of preservationo Aqueous 

 extracts of flesh ^nd viscera could be kept, for 2 or 3 weeks at tem= 

 peratures at or just above the freezing point without excessive 

 putreiiction and loss of aotivityo Aqueougi extracts could be preserved 

 indefinitely in a Z^percent solution of sulphur dioxide gaSj, sulphuric 

 acidj, phosphoric acidp or sodiiim bisvilphlte; apparently these chemi- 

 cal preservatives were not repul&ive to the fisho Alcohol extracts 

 could be kept indefinite lyo Both water and alcohol extracts could be 

 boiled to drynesSp producing a. dark brown^ gummy residue which 

 could be kept without deterioration lor long periods of time^ p>aJticu= 

 larly if suspended on sodium chloride crystals; when the gum.my sub- 

 stance was re^dissolved in water it was still attractive to the fisho 



Pos sibility of Conditio ningjof^ the_ Fish 



The question arises as to what extent the typical response 

 to extracts of tunc flesh and viscera is promoted by a conditioning of 

 the tunny to life in captivity andp particul^irryo to the type oi food fed 

 and the method of feedingo 



The life of the tuna in the tank and pond differs greatly 

 from that in the seao The fishes' movements a-re linnited by the walls 

 and they fall into a pattern which is often precise and regular -much 

 different from that of the open seao Not only are their movements 

 limited horizontally but they are also limited vertically by the 

 shallowness of the water o 



S9 



