132 
This it undoubtedly is in many Teleosts, but in the Plaice 
it seems to correspond to palatinus and pre-trematicus ix. 
fused together. Otherwise there is no pre-trematicus ix. 
in the Plaice at all, or the whole of Jacobson’s anastomosis 
is that nerve, which is somewhat unlikely. 
The result, therefore, of the fusion of these two nerves 
is a large bundle formed in greater part of communis ix., 
but also to a lesser extent of communis vii. And as these 
two components consist of exactly similar fibres, the final 
course of each component can only be traced by degenera- 
tion experiments. The combined nerve (com. vid. + 22.) 
passes almost straight downwards on the inner side of the 
large pseudobranch and divides into an anterior branch to 
the mucosa of the roof and upper lateral wall of the 
pharynx, and a posterior branch to the mucosa of the 
ventro-lateral wall of the same. Although several of these 
branches passed close to the pseudobranch, none could be 
traced into it, as Herrick also finds in Wenidia. But the 
nerve fibres are of very fine calibre and difficult to follow, 
and as the pseudobranch has no other nerve supply it 
must derive its innervation frem this source, and’ indeed 
dissection shows that it does do so. But whether its fibres 
come from communis ix. or vil., or both, must be subse- 
quently determined. The large and_ well-developed 
pseudobranch, however, may well explain the size of 
Jacobson’s anastomosis. 
Near the origin of the post-trematicus some motor 
branches are given off from the Truncus hyomandibularis 
as in Menidia and Gadus. ‘The truncus then passes out- 
wards and downwards, and enters a canal in the hyoman- 
dibular bone, as in Gadus. Soon afterwards it gives off 
behind a lateral line nerve known as the :— 
8. Ramus opercularis superficialis vii. (op. s. v2z.).— 
This at once gives off two twigs which supply the last two 
