THE NERVOUS SYSTEM OF AMPHIBIA 265 



of the facial to the ascending tracts of the postauditory lateral 

 line roots is shown in figure 61, where the tract VII a is most 

 dorsal of the series. Between this and tract VII b is the dorsal 

 division of the postauditory roots. Most ventral in the set is 

 the ventral division of the latter. Good silver impregnations" 

 in longitudinal section make it appear that these tracts may all 

 be considerably longer than figure 6 represents them. 



2. The visceral sensory component. The geniculate ganglion is 

 now in contact with the ectoderm by only a slender column of 

 cells which rests also upon the entoderm. This ectodermal con- 

 tact of the ganglion lies about midway between two other pro- 

 jections of the ganglion: the one contributing fibers to the r. 

 hyomandibularis as the latter passes ventrad in very close rela- 

 tion with the caudal wall of the spiracular pouch (fig. 4, e); the 

 other, directed rostrad on the dorsal surface of the entoderm, 

 giving off a well defined r. palatinus (fig. 4, d). This nerve passes 

 mesad and a little rostrad over the pharyngeal cavity almost to 

 the middle line and forward to within abougt 50 n of the rostral 

 end of the foregut. 



The root fibers of the geniculate ganglion enter the brain ven- 

 trally of the lateral line roots, as seen in figure 56 {R.VII,Vis.) 

 and then turn caudad as the fasciculus solitarius (fig. 6, Fas.SoL). 

 The tract still lies immediately against the limiting membrane. 

 It is distinctly larger than in the coiled-reaction stage. 



3. The auditory organ and nerve. The endolymphatic append- 

 age is more sharply differentiated from the body of the auditory 

 vesicle than it was. in the earlier stage, and is still closely pressed 

 against the brain (fig. 79). The auditory ganglion and nerve 

 extend to the caudal border of the vesicle in the position shown 

 in figure 79. In silver impregnations the fibers of the nerve now 

 appear as exceedingly fine filaments which become closely merged 

 with the basal ends of the epithelial cells or with a basement 

 membrane which is also slightly impregnated. Nerve ending 

 upon the epithelial cells of the vesicle, however, have not been 

 observed. 



The root fibers of the auditory ganglion, entering the brain as 

 shown in figures 57 to 60, form a descending tract which extends 



