No. I.] THE CRANIAL NERVES OF AMPHIBIA. l6l 



That ventral half oi the lateral line component of the Facialis 

 which apparently unites with the VIII, actually, we have seen, 

 unites with the motor and fasciculus communis portions of the 

 VII, thereby forming the trunk of the Hyomandibularis. It is 

 distributed, we have seen, in the tadpole to lateral line organs 

 lying along the side of the head, and also to a line proceeding 

 around under the ventral side. Here, again, we have in Urodela, 

 as is evident from Osborn's account, a similar division of the 

 lateral component ("VII/"), but it is not certain, in all cases, 

 exactly into what branches it finally passes, for the arrange- 

 ment of the organs is, apparently, different, a fact not surpris- 

 ing when the anatomical differences obtaining between the 

 tadpole and Urodela are considered. 



In general, according to Fischer, the arrangement of the 

 Facialis in Urodela is as follows : A reenforcing branch is 

 sent forwards to the Trigeminus, as above discussed. The re- 

 mainder sends off the R. palatinus and, further along, the R. 

 alveolaris. The discussion of these branches properly comes 

 in another place. Besides these, there are two principal 

 branches, the R. jugularis and the R. mentalis. Either before 

 the separation into these latter two branches or from the R. 

 jugularis, twigs are given off to the M. digastricus. The R. 

 jugularis receives a communicating branch from the IX and 

 supplies the M. mylohyoideus posterior and the subjacent skin. 

 The R. mentalis divides into a branch along the side of the 

 lower jaw, and another branch more mesal. A comparison 

 with the figures of Amblystoma and of the tadpole will, I think, 

 make the homologies perfectly clear. In the tadpole the com- 

 municating branch from the IX is received before the VII 

 divides (as is also the case in some of the Urodela) into the 

 R. hyoideus to the M. mylohyoideus and adjacent skin, which = 

 the R. jugularis and the R. mandibularis externus, which =the 

 R. mentalis. Consequently the R. mentalis is the branch 

 belonging to the lateral line system. This homology must be 

 taken with the provision that other fibres, such as general 

 cutaneous fibres from the communicating branch from the IX, 

 may also compose a part of the R. mentalis. A partial mingling 

 of this kind we have found exists in the tadpole. Only a 



