FISHES 1 1 1 



Can it move backward ? How are the fins set in motion ? 

 What is the colour of the flesh, or muscles, of a fish? Count 

 the fins. How many are in pairs ? (Fig. 209.) How many- 

 are vertical ? How many are on the side ? How many 

 are on the middle line? Are the paired or the unpaired fins 

 more effective in balancing the fish ? In turning it from 

 side to side ? In raising and lowering the fish ? In pro- 

 pelling it forward ? How are some of the fins useful to 

 the fish besides for balancing and swimming ? 



The hard spines supporting the fins are called the fin 

 rays. The fin on the dorsal line of the fish is called the 

 dorsal fin. Are its rays larger or smaller than the rays of 

 the other fins ? The perch is sometimes said to have two 

 dorsal fins, since it is divided into two parts. The fin 

 forming the tail is called the tail fin, or caudal fin. Are 

 its upper and its lower corners alike in all fishes? (Fig. 228.) 

 On the ventral side, just behind the vent, is the ventral 

 fin, also called the anal fin. The three fins mentioned are 

 unpaired fins. Of the four-paired fins, the pair higher on 

 the sides (and usually nearer the front) are the pectoral 

 fins. The pair nearer the ventral line are the pelvic fins. 

 They are close together, and in many fish are joined 

 across the ventral line. The ventral fins are compared to 

 the legs, and the pectoral fins to the arms, of higher verte- 

 brates. (Fig. 244.) Compare fins of fish, pages 123, 124. 



Make a drawing of the fish seen from the side, omit- 

 ting the scales unless your drawing is very large. 



Are the eyes on the top or on the sides of the head, or on 

 both ? Can a fish shut its eyes? Why, or why not ? I s the eye- 

 ball bare, or covered by a membrane ? Is the covering of 

 the eyeball continuous with the skin of the head? Is 

 there a fold or wrinkle in this membrane or the surround- 

 ing skin ? Has the eye a pupil ? An iris ? Is the eye of 



