Basal Ganglia of Amphibia 115 



tilaginous or bony fishes. For instance, the 

 common bull-frog, in addition to a membranous 

 labyrinth such as exists in the auditory ap- 

 paratus of fishes, possesses the rudiments of a 

 structure known as the cochlea, which plays an 

 important part in the appreciation by the 

 animals of differences in sound. From experi- 

 ments made by Prof. Yerkes, it seems that 

 frogs appreciate differences in sound, as demon- 

 strated by their movements, and in an alteration 

 in the rate of their respiration when exposed to 

 differences of range of auditory vibrations. 

 That these movements depend on the action of 

 the auditory apparatus, and corresponding cere- 

 bral centres is shown by dividing the auditory 

 nerves of these animals that is, by destroying 

 the connection between their ears and auditory 

 cerebral centres; after this has been done, the 

 animal's movements in response to vibrations 

 of sound are abolished. 



Having in part adopted a terrestrial mode 

 of life, the olfactory organs of Amphibia have 

 become somewhat modified in response to the 

 altered nature of their environment; they 

 afford a direct passage for air to the animal's 



H 2 



