Cltral (#371) Teatoatarone (#501) 



Creatinine (#495) Threonine, DL (#461) 



Eucalyptol (#395, 513) Threonine, DL, with allothreonlne (#460) 



Glutamic acid hydrochloride, L (#519) Thiamine hydrochloride (#492) 



Glutamic acid monohydrate, DL (#452) Tonquin musk (#511) 



Glutarlc acid, alpha keto (#431) Tryptophane (#434) 



Gluten (#525) Tryptophane, DL (#458) 



Glycyl-glyclne (454) Tyrosine, DL (#490) 



Guanine (#435) Uracil (#494) 



Guanine hydrochloride (#464) Uraml (#465) 



Hexahydrobenzolo acid (#518) Vlosterol (Irradiated ergosterol) (#507) 



Hlstldlne (free base) (#448) Vitamin A, crystalline (#514) 



Hlstldlne monohydrochlorlde , DL (#432) Yeast hydrolysate (#520) 



Hydroxyprollne (#433) Xanthophyll oil (#457) 



lonlne, alpha methyl (#508) 



There was no positive response to any of the above substances. In a 

 few (#365, 413, 498, 503) , activity simulating a response was noted, but this may 

 have been caused by extraneous factors or it may have been'a curiosity about or 

 sensing of some of the strong smelling materials. In others of a bright orange 

 color (#510) or a dark green color (#459) there was an avoiding or repellent ef- 

 fect which was obviously visual in origin. 



Discussion 



In view of the results given in a proceding section which indicate that 

 the response to extracts of "food substances may be partially conditioned by the 

 particular type of food fed, it seems worchwhile to speculate further on the part 

 which conditioning may play in causing all responses in the pond. The so-called 

 "attractant" to tuna may be a complex of substances which are present in one 

 grouping or another, and to a greater or lesser extent, in extracts of many marine 

 animals such as fish, squid, shrimp, or even plankton. Certainly the tuna in the 

 pond have become accustomed to being fed on dead material--so much so that they 

 Ignore live bait in the pond. Possibly they have associated the act of feeding 

 with the smell or taste of this "attractant" which is released into the water 

 from the cut-up food material when it is thrown to them at feeding time. Thus they 

 may exhibit a conditioned feeding response when stimulated by this "attractant" 

 which is present in the extract. This would be a possible explanation of why they 

 respond to extracts of one material when another is being fed. In addition, a 

 further conditioning to a particular substance or complex of substances in a par- 

 ticular food organism could conceivably take place. If so, this would explain why 

 they show a heightened response to extracts prepared from the particular food sub- 

 stance which they are being fed. It was hoped that even if this were so, wild 

 fish at sea might be naturally "conditioned" to a smell given off by the whole, 

 live organisms on which they feed, particularly if the organisms were occasionally 

 injured diu'ing the feeding process and gave off attractive body juices. More in- 

 formation on the part played by conditioning, natural or otherwise, might be ob- 

 tained from pond experiments if the tunny would feed on live bait. As they will 

 not do this (unless the bait is caught and thrown to them), the only other obvious 

 way to settle the question Is to present the extracts to wild fish at sea and to 

 study their response. 



POND EXPERIMENTS WITH EDIBLE LURES 



As the tuna in the pond were accustomed to being fed with materials 

 thrown to the surface by an attendant, they showed a strong visual response to 

 objects which suddenly appeared on the surface and also to persons who approached 

 the edge of the pond. This conditioned behavior made it difficult to perform 

 meaningful experiments in the field of visual and visual-chenlcal stirrulation 

 (Hsiao and Tester 1954). Inedible objects such as leaves falling to the surface 

 or stones thrown to the surface would attract the fish If they were within about 

 50 feet of the object (the tunny have a keen sense of vision). They would dash 

 after such objects, snap at them, and sometimes take them into their mouths but, 

 as nearly as could be observed, would then reject them. It would have been possi- 

 ble to devise experiments to study the response to inedible objects of different 



