6o The Life Story of the Fish 



to a stop, and they cannot back water very successfully. The 

 advanced fishes, like the black bass and the striped bass, 

 have more flexible fins, and the position of the ventrals up 

 forward under the pectorals makes them of more use in 

 maneuvering. It is easy to see that by thrusting one ventral 

 straight down and giving a flip of its tail, the bass can spin 

 around as if it were on a pivot. Trout spend a great deal of 

 their time heading in one direction, upstream, and most 

 things come at them from the direction in which they are 

 headed, whereas bass live in quieter water, swim in all di- 

 rections, and have to be ready to spin around to any point 

 of the compass to confront enemies or food. However, this 

 line of thought should not be carried too far. The trout, 

 fishermen will agree, can turn around quickly enough if it 

 has to, whereas the shark, with no directional influences in 

 its life, is a pretty lumbering maneuverer. 



And in the delicate movements whose precision fascinates 

 us, the fins play the major r51e. No one who has ever 

 watched fishes can help being aware of the fact that they 

 have a control of their own bodies in their own element 

 unequaled by any other animal. Birds are the nearest ap- 

 proach, with their ability to fly and to soar, but the fish is 

 their master. He can move imperceptibly forward a fraction 

 of an inch, or shoot forward from a standing start with light- 

 ning speed. He can go straight up and straight down. He 

 can go backward. He can even remain suspended absolutely 

 motionless in the water for an indefinite length of time, and 

 while this stationary position depends upon the equilibrium 

 between the fish and the water which we spoke of earlier, it 

 also calls the fins into play. For the fish must breathe, and 

 his method of breathing is to pass water backward over the 

 gills and out through the gill openings. This backwardly 

 directed current tends to move him forward, and must in 

 most cases be counteracted by backing water with the fins. 



