No. I.] THE CRANIAL NERVES OF AMPHIBIA. ijc) 



2. One or usually two broad-fibred roots arising from the 

 tuberculum acusticum (=lobus posterior medullae oblongatae, 

 Stannius = corpus restiforme = dorso-lateral tract, Gorono- 

 witsch). One of these passes forwards over the Trigeminus 

 proper and Gasserian ganglion and there divides into the supra- 

 orbital R. ophthalmicus superficialis and the infraorbital R. 

 buccalis. The other root, nearest the Acusticus, unites with a 

 motor root, and passes into the hyoideo-mandibularis — the 

 Facialis proper. 



3. A root, most dorsal of any, from the lobus trigemini 

 (= lobus impar). This root divides in such a way as to send 

 fibres to both divisions of No. 2. While that part of No. 2 

 joining the Trigeminus does not seem to necessarily form an 

 intimate union with the latter, No. 3 seems to completely 

 mingle with No. 2. Besides mingling with the latter, however, 

 No. 3 in some cases forms a R. palatinus and a R. lateralis, 

 besides other smaller branches. Often the R. ophthalmicus super- 

 ficialis VII appears to be especially connected with this root. 



4. A broad-fibred motor root close to the Acusticus and 

 passing exclusively into the hyoideo-mandibularis. 



5. In some cases, at least, a fine-fibred root from the lobus 

 vagi (Goronowitsch). 



The N. lateralis vagi always arises by a broad-fibred root 

 from the tuberculum acusticum, dorsad and cephalad of the 

 other roots of the IX + X. 



I may add here that this arrangement of the roots is con- 

 firmed by my own dissections of Selachians. 



It is No. 2 which innervates the lateral canals in all cases, a 

 fact which Stannius seems to have clearly recognized, though 

 he does not always seem to have distinguished clearly between 

 its branches and those of the Trigeminus proper. Marshall 

 and Spencer, and Van Wijhe, I believe, were the first to make 

 this clear. The fact that the Trigeminus proper does not par- 

 ticipate in the innervation of the lateral-line system has also been 

 brought out by Allis (Amia), by Ewart (Laemargus and Raja), 

 and by the writer (tadpole). 



It is very evident from the above that the lateral-line system 

 of nerves are alike in their main arrangement in all the forms 



