in the Fish Gallery of the Indian Museum. 31 



in the Shark. The olfactory nerves are really out- 

 growths of the brain. 



From the under surface of the optic lobes the optic 

 nerves pass : they too are really outgrowths of the brain. 

 In the Carp and Lamprogrammus the optic nerves cross, 

 so that the nerve of the right side goes bodily to the left 

 eye and vice versa : but in the Shark they fuse where 

 they cross each other. 



Eight other pairs of nerves emerge from the under 

 surface of the brain. They supply the muscles that 

 move the eye-balls ; the skin and muscles of the head, 

 face, jaws, gill-covers and hyoid ; the organ of hearing ; 

 the mouth, tongue, gills and throat ; and the gullet, 

 stomach, heart, air-bladder and lateral line. 



The Spinal cord is continued from the medulla oblon- 

 gata along more or less of the canal formed by the 

 neural arches of the vertebra?, and it gives off a pair of 

 spinal nerves between every vertebra. 



The dissections of brains in Case 1 1 also display some 

 of the organs of special sense — namely the organs of 

 smell and hearing and the eye. 



Except in the case of the Dipnoi, in which the nostrils 

 open into the mouth, the organ of smell in Fishes con- 

 sists of a pair of closed sacks of considerable size, the 

 lining membrane of which is pleated. 



Except in certain fishes that inhabit subterranean 

 pools or ocean depths to which no light can penetrate 

 (e.g., Tauredophidium Hextii 'in Case 15), eyes are present 

 in Fishes and are peculiar in having the cornea fiat and 

 the lens'spherical. 



The organ of hearing in Fishes is enclosed within the 

 bones of the head, and consists, on either side, of the 

 labyrinth or " internal ear " only. The cavity that 

 corresponds with the tympanum or " middle ear " of 



