THE FISHES. 179 



Before describing the various fishes, we would say a 

 few words on those organs by which their mental intelli- 

 gence and powers of movement are regulated. 



Naturalists and physiologists up to a very recent period 

 have placed the fishes into the lowest class of vertebrate 

 animals as regards their mental capacities. Professor 

 Rymer Jones, writing some thirty years ago, says : " We 

 are justified in anticipating that in intelligence, and in the 

 relative perfection of their senses, fishes should be less 

 highly endowed than the other vertebrate classes ; " and 

 he continues in another paragraph : "With such inferiority 

 in their powers of communication with the external world, 

 and with faculties so circumscribed, we might justly infer 

 that, as relates to their intellectual powers, fishes hold a 

 position equally debased and degraded." 



The observations of later years, owing to a much closer 

 investigation of their habits particularly in fresh-water 

 fish not only show that they have considerable mental 

 intelligence, but that they are able to exercise the powers 

 both of reason and deduction. 



The brain of a fish differs very considerably in capacity 

 from the higher vertebrata, and occupies but a small por- 

 tion of the cranial cavity, the interval between the cranium 

 and the brain being much less in young fish than in adults, 

 which proves that the brain does not grow in the same 

 proportion to the rest of the body ; indeed, it has been 

 observed by Cuvier and others, the size of the brain is 

 nearly equal in individuals of the same species, even al- 

 though the body of one is twice the size of that of the 

 other. The brain of a fish consists of several masses 

 placed one behind the other, either in pairs or singly ; these 

 masses may be regarded as so many distinct ganglia, the 

 complexity and perfection of which are gradually increased 

 as we proceed upwards in the scale. 



The cerebral hemispheres of all vertebrated animals are 

 supposed to be the seat of the mental powers. In the 

 higher animals, in quadrupeds, and more especially in man, 

 the proportionate size of the hemispheres of the brain 

 is so large as to conceal the ganglia and other parts ; 



