100 THE CATFISH. 



tween the two extremes is the trunk, not sharply distinguished 

 from either. Is there any region which could properly be called a 

 neck ? Arbitrary limits have been assigned to the three body 

 divisions, however; these will be discussed later. 



b) Observe the color of the catfish. Is there any good reason why the 



under parts should be much lighter than the sides and back? 

 Recall the appearance of the fish as you saw it swimming lazily 

 about near the bottom of a shallow pond. Place a live catfish in a 

 pail or box having a glass bottom and view the animal from 

 beneath, excluding from your eyes all light except that which 

 comes down through the water. 



c) Examine carefully the skin on different parts of the body. Is there 



any evidence of the scales you find in some fishes ? 



d) Running along each side of the fish is a row of small tube-like 



papillae constituting what is called the lateral line. Examine it 

 with a hand lens and determine its anterior and posterior limits. 

 Its intimate association with a prominent nerve beneath the skin 

 leads to the conclusion that its function is sensory. 



e) Observe now the organs of locomotion and equilibrium the fins. 



These may be divided into two classes those situated in the 

 sagittal plane of the body, and the paired fins corresponding to the 

 limbs of the higher vertebrates. How many fins of each class are 

 present in the catfish ? The one on the mid-dorsal line, just back 

 of the head, is the dorsal fin. Like all of the others, except one, 

 it is supported by fin rays. Behind this fin, near the tail, is the 

 adipose fin, a small projecting flap unsupported by rays. The 

 tail ends in a caudal fin, forked in some fishes, truncated or 

 rounded in others. What is the form in your specimen ? Do you 

 know any fish in which the upper fork is much longer than the 

 lower ? In front of the caudal fin, on the under side of the body, 

 is the anal fin. 



f) The paired fins are more lateral in position. The front pair 



pectoral fins is connected with a firm girdle of bones encircling 

 the body in that region. Prove this by feeling these structures. 

 Determine also the extent of the "girdle" to which the hindermost 



