I believe he is rising now from some management of the air-bladder.
The air-bladder large and strong, and in some cases notched on the margin.
But the primal purpose of the air-bladder was not to serve as a float.
In the sharks, rays, and chimæras there is no trace of an air-bladder.
The elasticity of the air enables fishes to rise and sink in water, through the action of ...