430 Julia B. Platt 
capsule is developed only in its dorsal part and at the anterior and 
posterior margins. Through the posterior and smaller of the two 
notches, seen in fig. 16 in the margin of the inner wall of the capsule, 
the ductus endolymphaticus passes dorsalwards from out the 
otie chamber. The trigeminal ganglion lies between the auditory 
capsule and the quadrate cartilage. The roots of the facial and 
auditory ganglia are median to the large opening in the inner wall 
of the auditory capsule, through which the auditory nerves pass 
directly to the membranous ear, while the hyomandibular and palatine 
branches of the facial nerve accompany the auditory nerve into the 
capsule, passing outwards through the two anterior of the three open- 
ings in the floor of the capsule, seen in fig. 15, the smallest opening 
being that for the palatine nerve. The ganglion of the facial element 
of the lateral-line system lies median to the anterior part of the 
inner wall of the auditory capsule, the nerves from the ganglion 
passing dorsalwards and forwards near the trigeminal ganglion. 
Median to the posterior wall of the capsule lie the roots of the 
glossopharyngeal and vagus nerves, which pass outwards through 
the space between the occipital arch and the auditory capsule. 
The posterior and largest opening in the cartilaginous floor 
of the auditory chamber is that of the fenestra ovalis. The 
position of this opening is seen in transverse section in fig. 17, where 
it is also seen that were the inner wall complete, the auditory capsule 
would form in section a nearly equilateral triangle with rounded 
corners. As testified by all who have employed modern methods of 
study, the fenestra ovalis is not a secondary opening in the 
cartilaginous case of the ear, but is from the first merely closed by 
a membrane. 
At the stage represented in fig. 15 (i. e. 19 mm in length), the 
operculum! is unchondrified, and is not shown in the model. The 
Anlage, however, is already established in procartilage, and one 
finds that the operculum in Necturus, is neither part of the 
primitive otic capsule, nor formed in the membrane closing the fenestra. 
It arises independently. SröHr (80) tells us that in Triton and 
Siredon, the operculum is an outgrowth cut off from the margin 
1T regret the employment of the term »opereulum« to designate struc- 
tures so widely different as the covering of the gills, and a cartilage lying in 
the fenestra ovalis, but know not what word to substitute, since this carti- 
lage is not the equivalent of the »columella« of the Anura, and is of questionable 
homology with the »stapes« of higher Vertebrata. 
—_— Ss u 
