470 COMPARATIVE ANATOMY AND PHYSIOLOGY. 



is expressed by the fact that the most internal portion 

 now projects into the cranial cavity. 



In no fish is there anything more than a rudiment 

 of the cochlea (Fig. 198 ; A, c). The highest condition 

 of the amphibian ear is seen in the Anura ; though 

 we cannot yet speak definitely of a bony labyrinth, 



Fig. 198. Diagrams to show the Relations of the Auditory Labyrinth in 

 the Vertebrate Series. 



A, Pish ; B, bird ; c, mammal ; u, utriculus, with the three semicircular canals ! 

 s, sacculus: c, cochlea; r, aquaeductus vestihuli ; 6, lagena; cr, canalis 

 reuniens. In c, r is seen to divide into separate passages for the utriculus 

 and sacculus ; the vestibule is seen to have a caecal sac at v ; k, coil of the 

 cochlea. (Af te r Waldeyer.) 



yet we can, in the frog, see that the membranous laby- 

 rinth within has an influence on the contour of the 

 surface of its bony and cartilaginous capsule. Two 

 foramina, the f. rotund um and the f. ovale, are now 

 to be distinguished. Two tubular outgrowths are 

 given off from the periosteum of the perilymphatic 

 space ; both of them end in blind sacs, and one of 

 them (the ductus perilymphaticus) extends into the 

 jugular canal, and part of the neck of the sac is 



