CHAPTER XXVI. 

 THE BONY FISHES. 



In the age succeeding the coal period, the Ganoids be- 

 came small and scarce, and mostly confined to rivers and 

 estuaries, and soon the sea began to swarm with a new type 

 of fish-life, until at the present time there are in our muse- 

 ums nearly 10,000 species of new-fashioned bony fishes. 

 Our herring, menhaden, shad, mackerel, cod, etc., which 

 traverse the ocean in vast swarms, are modern creations. 

 Not only do the bony fishes stock the ocean, but they en- 

 liven our rivers, lakes, and ponds with myriad scaly forms. 

 What is there in this modern type of fish which has made 

 it so triumphant in life's struggle ? The fact is apparent, 

 but the causes obscure, and naturalists are just beginning 

 to discover them. 



One reason is their immense fertility. Thus the cod 

 deposits each year from eight to nine millions of eggs, and 

 the hake and haddock are probably only less prolific. While 

 most of the eggs and young fishes are snapped up by other 

 fish, many come to maturity — at least enough to stock the 

 ocean. And so on with other kinds of fish. 



Another reason is the adaptation of bony fish to every 

 variety of station in salt, brackish, or fresh water, and to 

 the diJEerent localities within these limits. Some are sur- 

 face-feeders, others remain at the bottom; there is a great 

 variation in the organs of digestion, in the shape of the 

 swimming-bladder, when it is present, but especially in the 

 shape and position of the fins. While no two kinds of fish 

 swim in exactly the same manner, the power of swimming 

 has been wrought out most thoroughly in the bony fishes, in 

 vfhJch Nature has exhausted every refinement and variety 



