126 PLECTOGNATHI. 



mouth, it presses the valve down, and thus distends 

 the cells, but the pressure from behind throws it 

 back, so that none of it can escape through the 

 external orifice. 



Just as it comes to the surface, it seems to inhale 

 a prodigious volume of air, that at once swells the 

 whole body into the shape of a balloon. Before 

 this, the body is comparatively slender. As the 

 fish may be rolled about like a foot-ball, bounding 

 and rebounding, when thrown, precisely in the 

 same manner; it evidently has not the pow- 

 er of allowing the air to escape. 



If stamped upon, the bursting causes a loud 

 report. In the sun, the swelling increases so rap- 

 idly, by the expansive force of the pent up air, 

 that the skin gives way with a sudden rent, accom- 

 panied with a loud noise. Thrown upon the wa- 

 ter, it floats away partly on one side, resembling 

 at a distance, (the belly being delicately white,) a 

 white foam. 



However, after a while the size begins to lessen, 

 till finally the fish succeeds in getting under wa- 

 ter again, and survives the trial. Probably the 

 temperature of the water has some agency in con- 

 densing the air, till the valve, or epiglottis, by its 

 own elasticity, re-acts, and by the openings, per- 

 mits the confined air to escape. 



The swell-fish varies from eight inches to one 



