100 Book of the Black Bass. 



— the body up in the air and the legs down in the water — is ex- 

 tremely doubtful. 



"The tank by which Dr. Hodgkinaon was enabled to demon- 

 strate his theories was made so that from one end the observer 

 could, by directing his vision from various depths of water, al- 

 ways look through a slip of glass placed at right angles to the 

 point toward which he looked. In this way, and by use of a little 

 figure to represent a man, the point where invisibility begins ( four 

 degrees) could be clearly seen, as well as the effect which the 

 water has of apparently lifting the object much above the position 

 which it occupies." 



Sense of Hearing. 



There is no external ear in fishes, the internal ear alone 

 existing, and which is extremely delicate in its construc- 

 tion. 



Dr. John Hunter observed that it varied much in the 

 different genera of fishes, but that in all it consisted of 

 three curved tubes, -which united one with another. The 

 whole organ is composed of a kind of cartilaginous sub- 

 stance, and in some fishes is crusted over with a thin 

 lamella to keep it from collapsing. 



The canals terminate in a cavity, in which cavity there 

 is a bone or bones. These ear-bones are familiar to most 

 anglers, and are sometimes very beautiful, resembling 

 porcelain, and are often called "brain-ivory;" those of 

 the sheepshead (Aplodinotus grunniens) of our western 

 waters are known as " lucky stones," and are highly prized 

 by boys as pocket pieces. 



It is the rule among physiologists to say, that while fishes 

 can hear sounds produced in the water, they are incapable 

 of hearing those produced in the air, and even to limit their 

 capacity for hearing accurately those produced in the water. 



