44 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. 80.—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 
