THE EAR OF AMBLYOPSIS. 101 



each has its ampulla fully developed. The three ampullae and the sinus utriculus 

 superior communicate with the utriculus in front, behind, and above. Below, the 

 utriculus communicates with the sacculus, which terminates posteriorly in an 

 appendage, the lagena. The three ear bones are present, one in the recessus 

 utriculi, one (the largest) in the sacculus, and the other in the lagena. 



The auditory nerve divides into two branches, the ramus anterior and the 

 ramus posterior. The ramus anterior divides into three branches — the ramulus 

 ampulla? anterioris, which extends to the anterior ampulla; the ramulus ampullae 

 externae, which extends to the external ampulla; the ramulus recessus utriculi, 

 which extends to the recessus utriculi. The ramus posterior gives off a heavy 

 branch, the ramulus sacculi, which extends to the sacculus. The rest of the ramus 

 posterior divides into the ramulus lagenae, which extends to the lagena; and the 

 ramulus ampulla posterioris, which extends to the posterior ampulla. Another 

 branch, the ramulus neglectus, which is normally given off where the ramus pos- 

 terior divides into the ramulus ampulla posterioris and ramulus lagenae, has not 

 been identified. 



The normal fish ear has seven auditory spots — the macula acusticus recessus 

 utriculi, three cristas acusticus ampullarum, macula acusticus sacculi, papilla 

 acusticus, and the macula acusticus neglecta. In Amblyopsis all of these auditory 

 spots are present. 



