No. I.] THE CRANIAL NERVES OF AMPHIBIA. 1 57 



ing the region thus innervated in the tadpole. It is in general 

 the opercular region; and when, with the loss of gills, etc., it 

 either disappears or is largely reduced, the nerve supply is 

 correspondingly diminished. Thus in the higher forms we 

 have here not only a disappearance of the lateral-line nerves, 

 but a reduction of the general cutaneous nerves of this region. 



The homologies of the R. communicans ad facialem present 

 considerable difficulty. In Petromyzon we have a branch, 

 described by Ahlborn and others, which runs around outside 

 the auditory capsule and connects the VII with the IX + X. 

 This branch, however, belongs, according to the observations of 

 Ahlborn, Dohrn (15), and others, to the lateral-line system, and, 

 consequently, cannot be the homologue of the R. communicans 

 ad facialem in the tadpole and frog. This is still further 

 brought out by the fact that while in the tadpole and frog this 

 branch is given off by the IX + X, and passes forwards to 

 reenforce the VII, in Petromyzon the reverse is what occurs, 

 the communicating branch here being given off by the VII and 

 passing backwards around the auditory capsule to reenforce the 

 IX + X, forming a considerable part of the N. lateralis. 

 Kupffer considers this nerve to be a remnant of the " epi- 

 branchial " commissure found in Ammocoetes. This view can 

 be best discussed under the consideration of the III component. 

 (See, also, p. 200.) 



Goronowitsch(28) describes a communicating branch between 

 the Facialis and the Glossopharyngeus. The nature of this 

 branch can be also best considered later. From his description 

 it would not contain cutaneous fibres. 



In Urodela there are described two communicating branches 

 between the IX + X and the VII. One of these, a fine branch, 

 is considered to be the cephalic part of the sympathetic; while 

 the other, stouter branch, does not seem to be always present 

 (Fischer, Hoffmann). Respecting the latter, Fischer (20) 

 remarks that it might pass into either the cutaneous or mus- 

 cular twigs of the facial branch with which it unites ; and, 

 further, according to Volkmann's researches (64), it contains no 

 motor fibres. This agrees with the results above obtained, and 

 this branch is probably the homologue of the R. communican.s 



