PIKE. 623 



is longer wlien the fishes fly against than with or at an angle 

 to the wind. Any vertical or horizontal deviation from a 

 straight line is not caused at the will of the fish, but by cur- 

 rents of the air ; thus they retain a horizontally straight 

 course when flying with or against the wind, but are carried 

 towards the right or left whenever the direction of the wind 

 is at an angle with that of their flight. However, it some- 

 times happens that the fish during its flight immerses its 

 caudal fin in the water, and by a stroke of its tail turns 

 towards the right or left. In a calm the liue of their fiight 

 is always also vertically straight, or rather parabolic, like the 

 course of a projectile, but it may become undulated in a 

 rough sea, when they are flying against the course of the 

 waves ; they then frequently overtop each wave, being car- 

 ried over it by the pressure of the disturbed air. Flying- 

 fishes often fall on board of vessels, but this never happens 

 during a calm, or from the lee side, but during a breeze only, 

 and from the weather side. In daytime they avoid a ship, 

 flying away from it ; but during the night, when they are 

 unable to see, they frequently fly against the weather-board, 

 where they are caught by the current of ah, and carried 

 upwards to a height of 20 feet above the surface of the 

 water, while, under ordinary circumstances, they keep close to 

 it. All these observations point clearly to the fact that any 

 deflection from a straight course is due to external circum- 

 I stances, and not to voluntary action on the part of the fish. 



Tenth Family — EsociDiE. 



Body covered with scales; 'barbels none. Margin of the 

 upper jaw formed by the iniermaxillaries mesially, and by the 

 maxillaries laterally. Adipose fn none ; the dorsal fin belongs 

 to the caudal portion of the vertebral column. Stomach without 

 blind ^ sac ; pyloric appendages none. Pseudobranchice glandu- 

 lar, hidden ; air-bladder simple ; gill-opening very wide. 



