FISHES 121 



great many kinds of animals called fishes, but in this all of 

 them agree : all have some sort of a backbone, all of them 

 breathe their life long by means of gills, and none have 

 fingers or toes with which to creep about on land." ^ 



90. The regions and appendages of a yellow perch. — 



Study Figure 90 and notice that the body of the yellow perch 

 is divided into three regions ; namely, head, trunk, and tail. 

 Unlike the body of many animals, no neck is present, and the 

 head, therefore, is joined directly to the trunk. The line 

 of union of head and trunk is the posterior ^ margin of 

 movable flaps, called the gill covers, on the sides of the head. 

 Just behind or posterior to the gill cover on each side of the 

 trunk of the fish is a paddle-like organ called the pectoral fin. 

 On the ventral surface, below the pectoral fins, is a second 

 pair which are known as the pelvic fins. The pectoral and 

 pelvic fins are together known as the paired fins of the fish. 

 Besides these this animal has several unpaired fins, which 

 we shall now locate. On the dorsal surface notice two 

 dorsal fins, one behind the other, which project upward. 

 Below the posterior dorsal fin, on the ventral surface, is 

 another single fin called the anal fin. The tail region is 

 considered to begin just in front of the anal fin, since in the 

 fish the body cavity that contains the important organs of 

 digestion, circulation, and reproduction ends at this point 

 (Fig. 98). The anal fin, therefore, and also most of the 

 posterior dorsal fin, are attached to the tail region. At the 

 posterior end of this third region is the broad forked tail 

 fin. 



91. Regions and appendages of a goldfish. — Laboratory 

 study. 



1 Jordan's "Guide to the Study of Fishes," Vol. I, p. 3. 



2 The meaning of each of these terms is explained ia 6. 



