160 INTRODUCTION TO THE CLASS OF FISHES 



devised to be of no use whatever to any one save an ich- 

 thyologist. 



When this array confronts the general student, the pros- 

 pect is appalling. From the first page to the last, every tech- 

 nical work on fishes abounds in descriptive terms that to most 

 persons are about as attractive as the spines on a porcupine 

 fish. If the general reader attempts to master them, he soon 

 finds himself involved and discouraged, and the desired gen- 

 eral view of our finny tribes is obscured in fog. 



But the whole subject of fish study is merely a matter of 

 method. With fishes, as with the other vertebrates, the 

 Orders are the master keys by which a proper exhibit can be 

 unlocked and displayed. At the same time, the Subclass 

 divisions are of great importance, and must constantly be 

 kept in mind. Leaving out the deep-sea fishes, which we can 

 well spare for the present, there are twenty well-defined Or- 

 ders, the types of which are almost as easily known and re- 

 membered as a score of pictures in an art gallery.- The Orders 

 must not be lost sight of, for when they are firmly grasped 

 by the understanding and the memory the fog begins to 

 rise. 



GENERAL CHARACTERS. A typical fish is a cold-blooded 

 animal, with a bony skeleton, an elongated body which is cov- 

 ered with overlapping scales, and an outfit of fins for bal- 

 ancing, steering and propulsion. It has gills instead of lungs, 

 fixed eyes, and a swimming-bladder, and is specially fitted for 

 a wholly aquatic life. It is provided with teeth, it hears 

 sounds by the transmitting power of the bony plates of the 

 skull, and usually it lays eggs for the production of its young. 



