THE ALLIES OF THE PERCH 



323 



numbers of valuable food fishes and lobsters, and are a great 

 bother to the set lines and nets of commercial fishermen. 



Bony Fishes. The bony fishes, or Teleos'tomi (Gr. teleos, 

 " complete " or " perfect " ; stoma, " mouth "), in the higher 

 forms, of which the perch is an example, have the skeleton 

 ossified (converted into bone) and the body usually covered 

 with scales (Fig. 165) ; in 

 the lower forms the body 

 may be covered with bony 

 plates, and the skeleton may 

 be hardly more ossified than 

 in the group which has just 

 been considered. Inalltele- 

 ostomes, however, the gills 

 open beneath a protecting 

 operculum. Most of our 

 present-day fishes belong 

 to this order. 



The gar pikes of Ameri- 

 can waters illustrate one 

 type of body covering, con- 

 sisting of bony, enameled, 

 closely set plates, which form 

 a complete coat of armor. 

 The sturgeons (Fig. 166) il- 

 lustrate another type, in 

 which the armor is greatly reduced, the teeth absent, and 

 the animals adapted to bottom feeding by the development 

 of a beak, and by barbels for feeling for their food in the 

 mud. Sturgeons are found in Europe as well as in the United 

 States and Canada. One of the European species grows to 

 be over twenty feet long. 



The remaining bony fishes have fully ossified skeletons. 

 The eels are forms in which the body is greatly elongated 



Fig. 165. A scale from a muskel- 

 lunge. (Greatly enlarged) 



The numbered rings are annual growth 

 rings, showing that the fish bearing this 

 scale was in its eleventh year. (Photo- 

 graph by Dr. Alvin R. Cahn) 



