CoGHir.L, Cranial Nefves of Amblystoma. 217 



the r. maxillaris V, but in applying this term to the nerve in 

 Amblystoma I use it in a restricted sense discussed in Part 

 Second of this paper. 



^. — The Lateral Line Root. 



The area of exit of the lateralis VII root is divided into 

 four sections. Counting from the dorsal side, the first and third 

 sections are well separated from each other and project farther 

 caudad than either of the other two. The second section lies 

 chiefly between the first and third although it projects farther 

 cephalad than either. The fourth section lies close to the antero- 

 ventral margin of the third and extends farther cephalad and 

 ventrad than any of the other sections. From the first and 

 third of these sections arises the posterior division of the later- 

 alis VII root which enters the truncus hyomandibularis VII; 

 from the second and fourth sections arises the anterior division 

 of the same root which enters into relation with the trigeminus. 

 The neurones of the second section form the r. ophthalmicus 

 superficialis VII; those of the fourth section form the r. buc- 

 calis VII. It is evident, therefore, that the neurones of the rr. 

 ophthalmicus superficialis and buccalis tend to enter the 

 medulla farther cephalad than do those of the truncus hyoman- 

 dibularis. 



As the anterior division of the lateralis VII root emerges 

 from the medulla, it becomes compressed between the medulla 

 and the most dorsal and anterior portion of the posterior divis- 

 ion of the root. It does not at any point come in contact with 

 the auditory roots or with the motor or communis roots of the 

 facialis. It begins to separate from the posterior division of the 

 lateralis root at about the transverse level of the exit of the tri- 

 geminal root. In older specimens, it comes at the same time 

 into contact with the latero-dorsal side of the root of the tri- 

 geminus, but in younger larvae it is compressed against the 

 lateral margin of the dorsal rim of the medulla and cerebellum 

 to near the Gasserian ganglion. The ganglion of this root lies 

 on the dorsal surface of the Gasserian ganglion. The two gang- 

 lia axe so fused together that it is difficult to distinguish them 

 even with the aid of serial sections. 



