114 STRONG. [Vol. X. 



venience, together denominated the ^^ ventral VII,'' a name, as 

 seen immediately below, not applicable to some other forms. 

 There is one remarkable peculiarity in connection with this 

 root in the larvae and adults of Anura as contrasted with 

 Urodela. In the latter, as described by Osborn in Crypto- 

 branchus, its exit is just dorsal to the Acusticus, while in the 

 forrner, as described above, its exit is just ventral to the Acus- 

 ticus. This transference is probably connected with the change 

 in position of the Acusticus as noted above. 



These two roots fuse with the ventral side of the root of the 

 VIII so closely that tracing them in the tadpole is a matter of 

 some difficulty. 



The Acusticus shows the division into dorsal and ventral 

 roots described by Koppen (35). In the caudal part of the 

 former the fibres are smaller than those of the latter, which 

 are of varying sizes but contain some very large fibres. The 

 fibres of the dorsal root proceed obliquely ectad and ventrad, 

 and immediately pass within the auditory capsule and enter the 

 posterior portion of the auditory ganglion, which is composed 

 of small ganglion cells. The dorsal part of the ganglion 

 further cephalad, however, becomes composed of large gan- 

 glion cells which supply the coarser fibres of the auditory 

 branches. The posterior branch of the VIII consists of both 

 coarse and smaller fibres, as does the anterior, but the latter 

 branch seems to contain a larger proportion of coarse fibres. 

 The larger part of the dorsal root of the VIII seems to supply 

 the posterior auditory branch and the larger part of the ventral 

 root the anterior branch. 



The most dorsal fibres, belonging apparently to the cephalic 

 portion of the VIII at its exit, separate from the VI 11. They 

 form what was termed in the abstract the '^dorsal VIV or 

 " VII by This root can be seen to arise in part from fibres 

 running longitudinally in the dorsal part of the medulla at this 

 place. According to Osborn's observations on Cryptobranchus 

 (45) they ultimately arise from nuclei in this part of the 

 medulla. It may be remarked here, however, that the con- 

 nection between *' sensory " nuclei in the central nervous 

 system, such as those mentioned by Osborn, and the roots of 



