FISHES. 217 



It was estimated at one time that one fifth of the popu 

 lation of Holland were devoted to this branch of indus- 

 try alone. 



366. There have been various systems of classification 

 proposed for the Fishes. Cuvier first divides them into 

 those that have really bony skeletons, and those that 

 have cartilaginous ones. He then divides the Osseous or 

 bony fishes into two groups according to their fins, the 

 first being spine-rayed, the second soft-rayed. The Car- 

 tilaginous fishes he divides into two groups according to 

 the arrangement of their gills, the fringes being free in 

 the one, and being fixed in the other. Professor Agassiz 

 classifies fishes according to the character of their scales, 

 making four orders. 



367. It would take us into too broad a field to go into 

 the minute classification of fishes. I shall, therefore t in 

 addition to what has already been presented, notice par- 

 ticularly only a few of the most interesting of these 

 animals. 



368. The Swordfish, Fig. 169, is found in every part 



Fig. 169. The Swordfish. 



of the Mediterranean Sea. Its " sword" is an elongation 

 of the upper jaw, of great strength. It uses it in trans- 

 fixing its prey, running into shoals of fishes for this pur- 

 pose. In the British Museum there is a piece of the 

 bottom of a ship with a " sword" thrust entirely through 

 it. The length of this fish is from twelve to fifteen feet. 

 Another fish of about the same size has a similar projeo 



