138 THE WEALTH OF THE SEA 



dark, such as the cave-dwelling fishes, for example, 

 have only rudiments of an eye and are entirely blind. 

 Even the species living in shallow water where there 

 is an abundance of light generally have eyesight 

 rather poorly developed. Movements in the water 

 and no doubt some movements above the water are 

 detected, but it is doubtful that there is any accuracy 

 about their vision. 



The eye, as well as other organs mentioned, pre- 

 sents great variations. Some fish have very small 

 eyes, as in the star-gazers whose eyes are mere dots 

 on the dorsal surface of the head. In the catalufas 

 the eye is proportionately very large, for a specimen 

 eleven inches in length has an eye approximately one 

 and one eighth inches in diameter. 



The sense of hearing, like that of sight, appears 

 to be imperfectly developed. In fact, it is doubtful 

 if it consists of much more than detecting disturb- 

 ances in the water. Fish have no external ear, but 

 have an inner one, consisting of a chamber in which 

 are situated the ear-stones or otoliths. The sense 

 of hearing may be assisted in some species by certain 

 sense organs located in the lateral line that consists 

 of a series of pores along the side, connected with 

 tubes richly supplied with nerves. 



It has been quite definitely proven that some fish, 

 at least, can detect odors, but this sense is probably 

 even more imperfectly developed than sight or hear- 

 ing. Nostrils in fishes are visible externally only as 

 pits in the snout, or rarely they project in short 

 tubes; but they never have a communication with 

 the throat, as in the higher vertebrates. 



