THE PERCH 67 



ber band about the anterior (pectoral) pair of fins and 

 watch the result. Catch it once more and put the band 

 about the posterior (pelvic) pair of fins and watch the 

 result. After these experiments what can you say regard- 

 ing the functions of the different fins? Which fins are 

 used to maintain an equilibrium of the body ? 



Watch the movements of the mouth and gill covers. In 

 what order do the movements follow each other? What 

 is the reason for these rhythmic orderly movements ? 



Watch the eyes. Are they capable of movement ? Do 

 the eyes move together? Are the eyes furnished with 

 lids? Do they seem to have any means of protection? 

 Determine, if possible, the extent of vision. 



Place some food on the surface of the water. Watch 

 the fish obtain and swallow this food. Scatter small 

 pieces of paper on the water. Does the fish swim for 

 them ? Upon what sense does it seem to depend to find 

 its food ? Does it eat the paper ? Does it seem to have 

 the sense of taste? 



B. EXTERNAL FEATURES OF A FISH (perch). Note the 

 shape of the body from a dorsal and side view. What can 

 be said of its adaptation to swimming through the water ? 

 The body is flattened from side to side or compressed. 

 Like the earthworm, the perch is bilaterally symmetrical. 



Note the number, situation, size, and shape of the fins. 

 How many are in pairs? Where are the pairs borne? 

 How many are borne singly? Are these in the middle 

 line of the body ? How many dorsal fins are there ? The 

 front pair of fins is known as the pectoral fins and they cor- 

 respond to the front pair of limbs in the higher animals. 

 The more posterior pair are the pelvic fins. The single fin 

 just back of the anal opening is the anal fin. 



