BOWERS. — CRANIAL NERVES OF SPELERPES BILINEATUS. 185 



E. Facialis and Acusticus. 



1. Roots. — Apparently the roots of the facial and acoustic nerves 

 (PI. 1, Figs. 1, 2) agree with the condition in Necturus as described by 

 Kingsbury ('95) ; at least the relation of the several components as they 

 emerge from the brain is the same. Most caudal and ventral is the 

 motor root of the facial ( VII. rx. mot.),* formed from two rootlets of 

 deeply staining fibres, which arise from the median ventral region of the 

 medulla. Dorsal to this emerges the one large root of the acoustic 

 ( VIII rx.), and close to the dorsal side of the latter the fine unstained 

 fibres of the fasciculus-communis root of the facial ( VII rx. fas. com.). 

 At a little distance dorsad to these three roots and a little more cephalad 

 emerge the very coarse, deeply staining fibres of the lateral-line root 

 of the facial ( VII. rx. In. /.).f This is the "dorsal VII." of Strong. 

 The fibres of this root are not grouped into two distinct rootlets, as in 

 Necturus, though from the appearance of some sections there seems to 

 be a tendency toward such a grouping. Immediately on leaving the 

 brain the fibres of this component unite with those of the three roots 

 ventral to it, forming a continuous dorso-ventral sheet (Fig. 1). 



The dorsal root (VII. rx. In. I.), however, quickly divides, and its 

 more ventral fibres curve veutrad and laterad to enter the acustico- 

 facialis ganglion (gn. ac.-fac), while its more dorsal fibres pass directly 

 cephalad along the mesial surface of the ear capsule in the form of a thin 

 dorso-ventrally expanded sheet (compare Fig. 2), and enter the Gas- 

 serian ganglion. 



This dorsal part of the lateral-line root of VII. contains ganglionic 

 cells, which lie dorsal to those of the Gasserian ganglion proper, with 

 which, however, they become fused into a common mass. Nevertheless, 

 the fibres of this portion of the lateral-line root are clearly traceable 

 in their passage through the Gasserian ganglion, from which they emerge 

 as two. 



2. Branches. — (a) R. ophthalmicus superficialis ( VII. opt. suf.) 

 and (b) r. buccalis ( VII hue ) of the seventh nerve. Both of these 

 branches are distributed to lateral-line organs, the former giving off 

 numerous twigs throughout the whole of its course from the ganglion to 

 the tip of the nose. Ramus buccalis VII. has already been referred to 

 as following closely the course of r. maxillaris V. (see Fig. 2), though 



* By an oversight this is lettered in Fig. 1 as VI. rx. mot. 



t Not lettered in Fig. 1. In this figure it is almost directly below the lettering 



