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head, where the blind termination of it is covered 

 by the common integuments of the body. One 

 fish alone the Lepidoleprus Trachyrynchus 

 presents any appearance of a canal, proceeding 

 from the surface to meet the internal parts, as in 

 all animals above the rank of reptiles. But the 

 extreme simplicity of the auditory apparatus in 

 fishes and other aquatic animals, is precisely what 

 we should have looked for in beings destined to 

 hear through the medium of water ; the vibra- 

 tions of which, being so much more powerful 

 than those of air, would render the complicated 

 apparatus, requisite in terrestrial animals, in 

 them superfluous. 



Accordingly, it is in reptiles that we meet with, 

 for the first time, more or less constantly, not in- 

 deed a canal leading from the side of the head 

 towards the ear which none of them have but 

 one leading from the back of the pharynx, to 

 form a cavity, interior to which all the parts al- 

 ready described are situated. This cavity is 

 called the tympanum, and contains more or fewer 

 distinct bones, moved by proper muscles, and 

 serving to increase the impulse derived from the 

 vibrations of the air, and to convey it to the in- 

 ternal parts, which now take the name of laby- 

 rinth. Some additions, also, are now made to 

 this ; for, besides the three semicircular canals, 

 already described as branching from the common 

 bag in one direction, there is now a second series 

 of canals, of a very complicated structure, called 

 cochlea, branching in another, and affording, of 



