628 ALETS. [Vou. XII. 
o 
nerves to terminal buds in any region are split off from the 
ectoderm before the similar formation, in the same region, of 
nerves that supply the sense organs of the canal and pit lines. 
The branch of the glossopharyngeus to reach its destination 
runs first outward below the branches of the trigeminus and 
vagus and then medianward above them. 
The buds on the upper end of the operculum must be inner- 
vated either by the first dorsal branch of the vagus, by the 
hyoideus facialis, or by terminal extensions of the accessory 
branches of the trigeminus. Those on the gular plate and on 
the lower end of the gill cover are almost certainly innervated 
by those branches of the trigeminus that I have called ~ghs 
and v.ghi. The growth of the buds upward and backward from 
the lower part of the gill cover, corresponding to the direction 
of the branches of these two nerves, strongly indicates their 
innervation by them. If their innervation be by these nerves, 
the mandibularis internus facialis would probably take no part 
in the innervation of any of the buds on the outer surface of 
the head, and the nerve must be, in Amia, either a general cuta- 
neous nerve or a nerve like the palatinus facialis destined to 
supply terminal buds in the mouth cavity, as Strong supposes 
it to be. The almost total absence of buds along its course in 
Amia is, however, against this last supposition, and its course 
and position indicate strongly a nerve comparable to the one 
called by Pinkus branch 4 of the hyomandibularis in Protop- 
terus (No. 89, p. 304). As the nerve, in Amia, lies behind the 
spiracular canal it is a posttrematic branch of the facialis, and 
cannot, therefore, be the chorda tympani, for the course of that 
nerve in man through the upper portion of the tympanic cavity 
and then downward anterior to that cavity certainly indicates 
that it is a prespiracular nerve. That this nerve, in Amia, is 
the homologue of the nerve of the same name described by 
Ewart, Pollard, and Strong in other Ichthyopsida, and consid- 
ered by them as the homologue of the chorda tympani, is 
hardly open to question. The nerve in Amia is probably to 
be compared to the branch which, on each of the branchial 
arches, runs downward over the anterior face of the arch onto 
the inner surface of its ventral portion. Its position in Amia, 
