226 MARINE BIOLOGICAL LABORATORY. 



accessory apparatus is a ponderous mass, which only 

 relatively powerful vibrations can set in motion. All 

 vibrations of the air which do not succeed in moving 

 this conducting apparatus are lost to us. It is for the 

 purpose of making up this great loss that the external 

 ear has been developed. Traces of accessory apparatus 

 to place the internal ear in more favorable communi- 

 cation with the exterior, begin to make their appearance 



Fig. 17. — A projection of the internal ear on a flat surface, to illustrate 

 the relations of the sense-organs and canals of the Torpedo ear, when 

 the auditory chamber is brought to the surface and spread out flat. 



c Canal. n" Macula neglecta. 



po Canal pore. tnl Papilla lagense. 



n' Crista acustica. tns Macula sacculi. 



inu Macula utriculi. c. de Endolymphatic duct. 



among the cartilaginous fishes, whose ears still retain 

 their direct connection wTth the sea-water by means 

 of an endolymphatic duct. This tendency is due to 



