THE MIND OF FISHES. 59 



character of the brain of the fish indicates a low order of 

 intelhgence, both on account of its smalhiess and its 

 shape. Of all the vertebrata, the cerebral hemispheres 

 of fishes bear the smallest proportions to other parts of 

 the structure. The brain of the carp is said to be pro- 

 portionately the largest, and this fish is described by- 

 Walton as " a very subtle fish." Dr. Carpenter has the 

 following on the brains of fishes : — 



On opening the skull of a lish we usually observe four nervous masses 

 (three of them in pairs) lying one in front of the other, nearly in the same 

 line with the spinal cord. Those of the first pair are olfactory ganglia, or 

 the ganglia of the nerves of smell. In the shark and some other fishes 

 these are separated from the rest by peduncles, or foot-stalks. (A similar 

 arrangement is seen in the olfactory ganglia of man.) Behind these there is 

 a pair of ganglionic masses of which the relative size varies considerably in 

 different fishes (thus, in the cod they are much smaller than those which 

 succeed them, while in the shark they are much larger) ; these are the 

 cerebral hemispheres. Behind these again are two large masses, the optic 

 ganglia in which the optic nerves terminate. And at the back of these, 

 overlying the top of the spinal cord, is a single mass, the cerebellum ; this 

 is seen to be much larger in the active rapacious shark, the variety of whose 

 movements is very great, than in the less energetic cod. The spinal cord is 

 seen to be divided at the top by a fissure, which is most wide and deep 

 beneath the cerebellum, where there is a complete opening between its two 

 halves. This opening corresponds to that thfough which the cesophagus 

 passes in the invertebrata ; but as the whole nervous mass of vertebrated 

 animals is above the alimentary canal it does not serve the same purpose in 

 them ; and in the higher classes the fissure is almost entirely closed by the 

 union of the two halves of the cord on the central line. 



Thus it will be seen that the cerebellum, which is 

 supposed to be related to the purposes of motion, is 

 largely developed relatively, while the cerebrum, which 

 is supposed to be the peculiar seat of the intelligence, is 



