THE SENSE OF HEARING IN FISHES. 



71 



ears of no fewer than forty-eight species of fishes. The completely 

 differentiated internal ear of one of the higher fishes consists of a 

 utriculus (Fig. i, u) with its three semicircular canals and a sacculus 

 (sc) with its appended lagena (Ig). The utriculus is ordinarily 



Fig. 2. 



Fig. I. Left Ear of the European Perch, Perca fluviatilis, lateral view, 

 showing the three otoliths ; a, asteriscus ; /, lapillus ; Ig, lagena ; s, sagitta ; 

 sc, sacculus ; u, utriculus. After Retzius. 



Fig. 2. Left Ear of the European Perch, Perca fluviatilis, median view, 

 showing the sensory patches ; c, crista acustica ; /, lapilla acustica lagenae ; n, 

 macula acustica neglecta ; s, macula acustica sacculi ; u, macula acustica utric- 

 uli. After Retzius. 



connected with the sacculus by the utriculo-saccular canal. The 

 sense organs in this type of ear reach a maximum number of seven : 

 a crista acustica in the ampulla of each of the three semicircular 

 canals (Fig. 2, c), a macula acustica (n) in the utriculus and a 

 second one (s) in the sacculus, a macula acustica neglecta («) in 

 the utriculus, and a papilla acustica (/) in the lagena. No fish is 

 known to possess a papilla acustica basilaris cochlese or organ of 

 Corti, which makes its first appearance in certain amphibians and is 

 found in all higher vertebrates. Three otoliths are commonly pres- 

 ent in the ears of the higher fishes: a large one, the sagitta (Fig. i, 

 s) , on the macula acustica in the sacculus, a smaller one, the asteris- 

 cus (a), in the lagena, and a still smaller one, the lapillus (I), on the 

 macula acustica in the utriculus. 



