xIV CRANIAL NERVES 381 
pre-branchial nerve (visceral sensory), skirting the anterior 
margin of a cleft in its ventral course; and (7) a post-branchial 
branch (visceral motor) similarly related to the hinder margin. 
The first six cranial nerves resemble those of the higher 
Craniates in their mode of origin from the brain, in the -physio- 
logical nature of their component fibres, and in their peripheral 
distribution, and therefore they need not be specially referred to 
here. The principal branches of the fifth or ¢rigeminal nerve 
are shown in Fig. 218. Comparing this nerve with a typical 
branchial nerve it would seem that the profundus and super- 
ficialis ophthalmic nerves are dorsal nerves; the mawillaris and 
mandibularis, pre- and post-branchial branches, respectively, in 
relation with the modified gill-cleft which forms the mouth, 
while the branch to the oral surface represents a palatine nerve. 
The most important of the distinctive features in the cranial 
nerves of Fishes are to be found in the relations of nerves vil., 1x., 
and x. to branchial clefts, and in the lateralis system of nerve 
components and its association with the lateral line sensory 
organs. The seventh or facial nerve is an exceptionally interest- 
ing nerve. Besides the usual components of a typical branchial 
nerve certain of its so-called branches are wholly or largely 
derived from the lateralis system. For this reason the nerve 
may be said to consist of two portions, the facial proper, or 
those fibres which constitute the facial nerve in air-breathing 
Craniates, and the lateralis branches which solely innervate 
lateral line sense-organs, and are therefore peculiar to aquatic 
forms. The facial proper has a ganglion (the facial or geni- 
culate ganglion) on its root, and on entering the orbit. after 
traversing the cranial wall it gives off a palatine nerve. Just 
over the spiracle a pre-branchial nerve, the representative of the 
chorda tympani of Mammals, leaves the main trunk, and passes 
ventrally in relation with the anterior wall of the spiracle to 
its ultimate distribution in the walls of the mouth cavity. 
The main trunk, now called the ramus hyomandibularis, 
then pursues a ventral course behind the spiracle as a 
post-branchial nerve, and certain of its mainly motor branches 
which pass downwards in connexion with the hyoid arch 
supply _ the muscles of that arch, and, if an_ operculum 
is present, the opercular muscles as well. The lateralis 
portion of the facial includes the following principal branches, 
