BRAIN AND BODY OF FISH 



CHAPTER I 

 INTELLIGENCE AND BRAIN PATTERN OF BONY FISH 



The subject of behaviour in animals has in recent years attracted 

 the attention of biologists in this country and also in America, and 

 a large literature devoted to its discussion has arisen. Recent 

 studies on fish have been made at the Marine Laboratory at Ply- 

 mouth, in which experiments have been made to test the ability 

 of fish to master the intricacies of a maze. 



Another type of experiment has shown that if a predatory fish 

 and its prey are put in the same tank, but separated from each other 

 by a glass partition wliich prevents the hunter from reaching its 

 would-be victim, after a short time the fish will keep to its own side 

 of the partition, even after this obstacle has been removed. These 

 observations seem to prove that a fish has a capacity to learn, to 

 associate facts and direct its movements up to a certain point, 

 according to experience. Nevertheless, one hears not infrequently 

 the remark " I didn't know fishes had brains " ; and to illustrate the 

 brainlessness of fish, or perhaps their want of feeling or perception 

 of pain, the tale is told, how a fish hooked with a certain bait, may, 

 when returned to the river, be caught again with the same bait after 

 a short interval. This conclusion does not bear criticism, because 

 M'hen a fish is hungry or greedy, or, as a fisherman would say, is 

 biting freely, there is no doubt it appears stupid, but that same fish 

 when not hungry, will be most cautious in examining the bait and 

 subject it to the closest scrutiny, so that the finest gut and cleanest 

 bait are required to lure it to its capture. When hunger is in com- 

 mand, discretion is forgotten. As bearing on the intelhgence of 

 fish some remarkable studies have been recently made on the homing 

 instinct of salmon. The most convincing experiments have been 

 made on the cliinook or king salmon in Canada, where in the 

 Columbia River system we find the Lower Columbia River, ninety 

 miles long, receiving the water of two systems. The salmon fre- 

 quenting one system are " spring run," and those of the other are 

 *' autumn run " fish. If eggs were transplanted from one system 



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