Yerkes, The Sense of Heanng in Frogs. 



283 



labyrinth with its several sense organs. The labyrinth is consti- 

 tuted by three semicircular canals each of which has a sense-organ, 

 the Crista acustica, in its ampulla, the utriculus, the sacculus and 



Amp. lat. 

 Sacc. 



Ca. B. c. ant. 



Fig. I. Membranous labyrinth of Rana esculenta. After Gaupp's modifi- 

 cation of Retzius' drawing ; A, seen from the outside ; B, seen from the inside. 



the lagena, in which together there are five sense organs. 

 Figure i, a and b are reproduced from Gaupp's "Anatomic des 



