712 B. W. KUNKEL 



In older embryos, as already described, in addition to the canalis 

 perilymphaticus is also the canalis hypoperilymphaticus opening 

 into the cochlear cavity from the sulcus supracristularis. 



INTERIOR OF CAPSULA OTICA 



The interior of the otic capsule (figs. 29 and 31) exhibits a com- 

 plicated form, but in contrast to that of Lacerta it is somewhat 

 simpler because of the absence of a septum intervestibulare and 

 the consequent differentiation of cava vestibuli anterius and pos- 

 terius. Besides this, the posterior development of the lagena 

 tends to make the interior more compact. It is possible to dis- 

 tinguish a cavum vestibuli with a cavum ampullare posterius, 

 laterale, and anterius, the three canales semicirculares, and 

 a cavum cochleae which communicates widely with the cavum 

 vestibuli. Of especial interest in comparison with Lacerta, in 

 addition to the absence of a septum intervestibulare and the 

 relation of the cavum cochleae, may be noted the sulcus in the 

 posterior wall of the cochlea in which the n. glossopharyngeus 

 is situated in its passage from the interior of the cranium to the 

 exterior. It is shghtly oblique in its course, extending slightly 

 ventrally from the median to the lateral side on the posterior 

 side of the cavum cochleae immediately below the recessus ampul- 

 laris posterior. 



The principal part of the total cavity of the capsule is repre- 

 sented by that of the vestibule. Medially the cavum vestibuli 

 extends to the median wall of the capsule, but the lateral wall 

 of the capsule forms only a part of its lateral boundary, the ver- 

 tically situated septum between the vestibulum and the canalis 

 semicircularis lateralis (septum semicirculare laterale) being 

 interposed in the space immediately in front of the recessus 

 ampullaris posterior and behind that of the lateral ampulla (s.s.L, 

 fig. 4). The roof of the cavum vestibuh is incomplete because 

 of the large foramen pro sinu superiore utriculi. The roof is 

 formed by the septa semicircularia anterius and posterius which 

 extend horizontally outwardly from the median wall of the otic 

 capsule and separate the canalis semicircularis anterior and pos- 

 terior respectively from the cavum vestibuli. The septum semi- 



