No. I.] THE CRANIAL NERVES OF AMPHIBIA. 207 



the innervation regions. In the preauditory nerves we have a 

 large general cutaneous element for the supply of the exten- 

 sive surface of that portion of the head, while the preauditory 

 supply for visceral surfaces is naturally comparatively small. 

 We have a large viscero-motor supply, however, for the en- 

 larged branchial (jaw) musculature. In the postauditory region 

 the general cutaneous supply is small, owing to a reduction of 

 the surface supplied, due to the breaking through of the gills, 

 and also possibly to encroachments by trunk nerves. On the 

 other hand, the visceral surfaces supplied are extensive and 

 these nerves correspondingly developed. 



The manner in which the auditory organ is interposed, as it 

 were, is evidenced by the many anastomoses around it. In the 

 tadpole, while one half of the lateral-line nerves is related to 

 the V, the other half comes into relation with a general cuta- 

 neous nerve from the IX + X (R. com. IX + X ad VII), 

 which unites with it in a manner similar to that in which the 

 first half of the lateral nerves unite with the V, and between 

 their respective branches similar parallelisms seem to exist. 



While the trunk nerve to the lateral line issues with the 

 IX + X, the parallel trunk nerve to the end buds of the trunk 

 (R. lateralis trigemini) has a preauditory exit. Furthermore, 

 among the fishes, the palatine nerve would appear to be formed 

 by a union of post- and preauditory nerves (Goronowitsch, 

 Pollard). The development of the auditory organ has probably 

 caused a separation of nerves formerly more closely connected. 

 This is evidenced also by the manner in which the lateral-line 

 nerves converge mesad of the auditory capsule just before 

 entering the medulla. Ayers (6) has brought forward reasons 

 for supposing that the acustico-lateralis system was originally 

 double. We might even go a step further and suggest the 

 possibility that it was once single. 



In any case, the general relations of the pre- and postauditory 

 nerves point, I think, to the conclusion that the auditory organ 

 is a neomorph interposed among the nerves and altering their 

 primitive courses. 



