2o6 A HISTORY OF FISHES 



of human behaviour. A man observes a ripe pear hanging 

 from a tree and moves his arm forward to grasp it, a definitely 

 conscious action following upon the sight of the fruit conveyed 

 to the brain by the eye. At the same time his mouth begins 

 to secrete saliva, his stomach to pour forth its digestive juices, 

 and other preparations for the meal are started, all as the result 

 of a visual impression. 



The two types of action just described have different centres 

 of control in the brain, the conscious action being controlled 

 by the cerebral hemispheres, the seat of mind, and the reflexes 

 by the cerebellum and other parts of the brain. As has been 

 previously pointed out, these hemispheres are relatively small 

 in fishes, but in higher vertebrates they become progressively 

 larger and larger and take more and more control of the lower 

 centres, until in man they occupy the greater part of the space 

 allotted to the brain. 



To a large extent, the fish must be looked upon as a reflex 

 machine. That is to say, most of its movements and other 

 activities are the result of reflex actions rather than conscious 

 thought. A fish moves, breathes, feeds, and reproduces, but 

 rarely thinks. The elaborate habits of courtship, and the care 

 displayed by certain fishes in building a nest as well as in looking 

 after the welfare of the young, suggests that some at least are 

 susceptible to the instincts and emotions exhibited by the 

 higher animals. Apart from rare cases of fishes trained under 

 conditions of domestication, instances of definite thought or 

 memory are very scarce and of more than doubtful authenticity. 

 The combining together of two or more kinds of fish for the 

 purpose of obtaining food or of attacking an enemy may perhaps 

 point to a certain degree of intelligence, although it is open to 

 question whether there is really any constructive thought or 

 reason in the matter. 



