.58 



Instincts, Habits, and Adaptations 



of the tail are continued until the whole body is out of the water. 

 When the tail is in motion the pectorals seem in a state of rapid 

 vibration. This is not produced by muscular action on the 

 fins themselves. It is the body of the fish which vibrates, the 

 pectorals projecting farthest having the greatest amplitude of 

 movement. While the tail is in the water the ventral fins are 

 folded. When the action of the tail ceases the pectorals and 

 ventrals are spread out wide and held at rest. They are not 

 used as true wings, but are held out firmly, acting as parachutes, 

 enabling the body to skim through the air. When the fish 

 begins to fall the tail touches the water. As soon as it is in the 

 water it begins its motion, and the body with the pectorals 

 again begins to vibrate. The fish may, by skimming the water, 

 regain motion once or twice, but it finally falls into the water 

 with a splash. While in the air it suggests a large dragon-fly. 



FIG. 120. Sand-darter, Ammocrypta clara (Jordan and Meek). Des Moines River. 



The motion is very swift, at first in a straight line, but is later 

 deflected in a curve, the direction bearing little or no relation 

 to that of the wind. When a vessel passes through a school 

 of these fishes, they spring up before it, moving in all directions, 

 as grasshoppers in a meadow. 



Quiescent Fishes. Some fishes, as the lancelet, lie buried in 

 the sand all their lives. Others, as the sand-darter (Ammocrypta 

 pellucida) and the hinalea (Julis gaimard), bury themselves in 

 the sand at intervals or to escape from their enemies. Some live 

 in the cavities of tunicates or sponges or holothurians or corals 

 or oysters, often passing their whole lives inside the cavity of 

 one animal. Many others hide themselves in the interstices of 

 kelp or seaweeds. Some eels coil themselves in the crevices of 

 rocks or coral masses, striking at their prey like snakes. Some 

 sea-horses cling by their tails to gulfweed or sea-wrack. Many 



