proteins. There was a good response when barium acetate was used, 

 the barium ion was removed by passage of the material through a 

 strong cation exchange column (Amberlite IR-120), and the filtrate 

 was tested (No. 216, 225). On the other^hand, strangely enough there 

 was no response with exactly the same treatment, but using barium 

 chloride (No, 218). When the material treated with phosphotungstic 

 acid was passed through a strong cation exchange column (Amberlite 

 IR-120), the filtrate was passed through a strong anion exchange 

 column (Amberlite lRA-400), and the eluate was tested (No, 223), there 

 was no response, although one was expected judging by the results of 

 previous tests o However, a weak response was obtained with the final 

 filtrate from a aeries of precipitations involving the use of both the 

 barium ion and sulphuric acid (No. 215), following the method of 

 Suzuki et ale (1909). 



Inconsistent or negative results were also obtained in 

 attempting to repeat the various purification and fractionation 

 techniques discussed above on a self-digested extract of ground skip- 

 jack viscera, preserved with sulphur dioxide, supplied by Hawaiian 

 Tuna Packers, Ltd, The extract itself promoted a strong response in 

 some experiments (No. 219), but only weak responses in others (Nos. 

 229, 230). It could be cooked under pressure (No. 236) or extracted 

 with alcohol (No. 235) without loss of its attractive properties, but it 

 could not be carried successfully through the various precipitation nor 

 ion adsorption processes (Nos. 232, 233, 234, 237, 238). 



As skipjack flesh was no longer available, attention was 

 directed at a study of extracts of bigeye tuna flesh. Simple alcohol 

 extracts gave good responses (Nos. 239, 240)^ However, weaJc or 

 negative responses were oDbtained when the purified materials were 

 passed through ion exchange columns (Nos. 246, 247, 248, 256, 257, 

 265). 



The negative results in these tests may have been due 

 either to loss or destruction of the attractant at some stage of frac- 

 tionation, or they may have been due to the moribund condition of the 

 fish prior to a January mortality. To examine the former possi- 

 bility a series of experiments with extracts of bigeye flesh was under- 

 tciken as illustrated in figure 12. The filtrate from alcohol extrac- 

 tion was treated with lead acetate to remove the proteins, and 

 filtered; the filtrate was treated with sodium chloride to precipitate 

 the lead as lead chloride, and was tested (No. 266) with an excellent 

 response. The filtrate from the sodium chloride treatment, when 

 boiled, gave only a slight response. Some loss may have been asso- 

 ciated with boiling after treatment with lead, although a repeat of the 

 procedure by heating on a water bath, rather than boiling, gave a 

 very strong response in a later experiment (No, 273). When part of 



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