156 Descriptive Zoology. 



forward and to the left. But the fish quickly makes an- 

 other stroke in the opposite direction, and as a result of 

 the two he may go straight ahead. The fish may simply 

 make the double stroke, right and left, and without further 

 strokes dart straight forward, but usually there is a suc- 

 cession of strokes by which it is enabled to pursue a 

 straight course. It should be noted that nearly all fishes 

 that can swim rapidly have a pointed snout to diminish the 

 resistance. Resistance to the motion of the fish is still 

 further reduced by the mode of overlapping the scales and 

 the coating of mucus. The fins, too, point backward. 



How the Perch Eats. The perch feeds on minnows, 

 worms, water insects, and larvae of various sorts, which it 

 catches and swallows alive. The extensibility of the mouth 

 is very great. The upper jaw can be protruded so that 

 the opening of ' the mouth is a wide circle, nearly as large 

 as the greatest circumference of the fish at any point. It 

 has been noticed that when the fish keeps the mouth closed 

 the snout presents a sharp point ; this is in marked con- 

 trast with the large opening shown when the fish is about 

 to ingulf its prey. It must be kept in mind that the fish 

 has no special organs of prehension, but must do all the 

 work of catching with the mouth alone. There are 

 numerous teeth, but they are not large, serving merely to 

 hold the struggling captive, and used little, if any, for either 

 tearing or masticating it. 



Digestive Organs of the Perch. The mouth narrows back 

 into the wide gullet, which is kept closed except when 

 swallowing. The gullet leads into a fair-sized stomach, 

 which ends blindly behind. The intestine arises from one 

 side of the anterior end of the stomach. At the begin- 

 ning of the intestine are three short blind tubes, the ceca. 

 The intestine takes one or two turns and terminates in 



