SWIMMING ANIMALS 



99 



rule. Jt only emerges by a jump so far that the front 

 wings are clear of the water and at once expanded. The 

 tail is then wagged vigorously to and fro, and thus, by 

 sculling action (for which the enlargement of the lower lobe 

 is helplul), increases the speed till suddenly the fish is drawn 

 up intu the air and remains in gliding flight with its wings 

 at rest and sometimes, for a distance of several hundred 



Fig. 18. — Showing position of fins of Flying Fish. A. When in full flight and 

 B. before reentering the water, the pelvic fins being depressed to reduce the speed 



of flight (after Hankin). 



metres, preserves a uniform height above the water. 



Occasionally, especially in cooler weather, slight fluttering 



of the wings does occur at starting, but the wings are nearly 



always at rest during the remainder of the flight ' ' (Fig. 1 8) . 



The flight is only a few inches above the water surface. 



In the sea horse the fins are often reduced to mere vestiges 



or are absent altogether. The fish is covered with a hard, 



H 



