lateralis ones, and they are said to have been definitely traced to certain opercular p it organs. In
Pleuronectes, Cole and Johnstone (’01, p. 132) also find th e nerve a purely lateralis one, its terminal
branches supplying an opercular line of p it organs.
Having given off this small branch the main truncus, in Scorpaena and Lepidotrigla, traverses
the facialis canal in the hyomandibular and issues on th e external surface of th e shank of th a t bone.
There it separates into its two parts, the ramus hyoideus and truncus mandibularis, the la tte r of which
soon separates into th e rami mandibularis externus and internus. The ramus hyoideus runs downward
and backward through th e opening between th e hyomandibular and the preopercular and so reaches
th e hyoid arch, its further course n o t being traced. The rami mandibularis externus and internus
run downward and forward across th e hyomandibulo-symplectic interspace of cartilage, and then
pass, respectively, through th e openings on th e posterior and anterior side of th e symplectic, as
already fully described, and so reach th e inner surface of th e palato-quadrate apparatus and then
th e mandible. The externus sends branches, as usual, to th e latero-sensory organs of th e preoper-
culo-mandibular line, and certain branches also to th e general tissues, th e nerve th u s n o t being a
simple latero-sensory nerve. The internus goes to th e inner surface of the mandible, its special distribution
and relations to th e other nerves not being investigated. Whether it contains communis fibers,
and those fibers only, as in Menidia, could n o t be determined, b u t, whatever its composition may
be, it is a tru e ramus mandibularis internus as th a t nerve is defined by Stannius. Herrick (’99, p. 171)
takes th e position, and it may be correct, th a t a nerve can not be a mandibularis internus unless
it contains communis fibers; and th e inference is th a t it must contain those fibers alone, for he says
th a t th e nerve is absent in Gadus notwithstanding th a t both Stannius and Cole describe a nerve in
th a t fish th a t is said to have th e topographical position of an internus. Neither Stannius’ nor Cole’s
descriptions of th e course of th e nerve being very definite, I have had th e nerve looked for in dissections
of Gadus merlangus, b u t it could not be found; which would seem to confirm Herrick’s conclusion
th a t th e nerve, when present, contains communis fibers only.
In Dactylopterus th e truncus hyoideo-mandibularis facialis does n o t traverse a single canal
in th e hyomandibular and issue on th e external surface of th a t bone, as it does in Scorpaena, Cottus,
Trigla and Lepidotrigla. When it reaches th e internal surface of th e hyomandibular the nerve, in
Dactylopterus, separates into its two portions, th e ramus hyoideus and th e truncus mandibularis,
th e la tte r of which alone traverses th e facialis canal through th e bone and issues on its external surface.
The ramus hyoideus simply passes beneath a bridge of bone on th e internal surface of the
hyomandibular and reappears on the internal surface of th a t bone. This will be further discussed
when describing th e bones in this fish. From th e truncus mandibularis, as it enters its canal in the
hyomandibular, a lateralis branch, accompanied by what are apparently wholly general cutaneous
fibers, passes backward through a small b ranch canal in th e bone, this nerve supplying th e two dorsal
organs of th e preopercular canal and the tissues on th e outer surface of th e opercular. The truncus
mandibularis contains communis fibers and is joined, after it reaches the outer surface of th e hyomandibular,
and as already stated, by th e communicating general cutaneous branch th a t issues
through th e trigeminus opening of th e trigemino-facialis chamber. After being joined by this communicating
branch, the entire truncus mandibularis passes to th e internal surface of th e palato-
quadrate through an opening th a t lies posterior to th e symplectic, no evident branch passing inward
anterior to th a t bone. There is thus no evident ramus mandibularis internus in this fish. The
mandibularis externus, after it reaches the internal surface of the palato-quadrate, certainly contains
fibers other than lateralis ones, but whether they are all general cutaneous ones, or partly communis,
could not be determined. If they are all general cutaneous ones, Dactylopterus would resemble
Ameiurus (Herrick, ’01) in this respect, the communis fibers that form part of the ramus mandibularis
facialis in that fish all being distributed to regions external to the palato-quadrate.
N E R V U S ACUSTI CUS .
The nervus acusticus has, in sections of Scorpaena and Lepidotrigla, two roots, which enter
the tuberculum acusticum close together, the slight swelling a t their point of entrance lying immediately
ventral to the swelling for the lateralis nerves. The anterior root belongs to the anterior
division of the nervus, the posterior root to its posterior division.
The anterior division, or ramus vestibularis, running forward sends, in my 55 mm Scorpaena,
two branches to th e macula aeustica sacculi. In th e 63 mm Lepidotrigla, one of the two branches
th a t go to this organ has a separate origin from the medulla, between the anterior and posterior roots
of the nervus, th e second branch arising from the posterior root. In both fishes, the ramus vestibularis
then sends a branch to the macula acustica utriculi, another branch to th e crista acustica in the
ampulla of the external canal, and then ends in the crista acustica of the ampulla of th e anterior
canal. All of these several branches separate distally into two parts, the two, parts of the two
nerves th a t go to th e ampullae supplying two separate and distinct organs in each of th e ampullae,
b u t th e nerve th a t goes to the utriculus supplying different p arts, only, of the large and continuous
utricular macula.
The posterior division of the nervus, or ramus cochlearis, runs backward and separates into
two parts one of which passes dorsal to the root of the glossopharyngeus and the other ventral to that
root. Thp dorsal branch supplies the two organs of the crista acustica in the ampulla of the posterior
canal, the ventral one supplying the two organs of the macula neglecta and also the papilla acustica
lagenae. The lagena is partially differentiated as a diverticulum arising from the dorsal surface of
the hind end of the sacculus.
The papilla lagenae and the maculae sacculi and utriculi each have related otoliths.
There was no indication of a ductus endolymphaticus in the dissections of Scorpaena, but in
sections, both of embryos and of the adult, a small remnant of the ductus is evident. In Trigla hirundo
the ductus is two or three times as large as in Scorpaena, being evident even in dissections. Retzius
(’81) shows the ductus in Trigla gurnardus.
N E R V U S G L O S S O P H A RY N G E U S .
The nervus glossopharyngeus of Scorpaena arises by a single apparent root, composed, as in
Menidia, of two bundles of fibers, a motor and a communis one.
After issuing from the medulla the root runs a t first posteriorly, then turns outward between
the dorsal and ventral branches of th e ramus cochlearis acustici, and then forward and laterally to
its foramen, passing between the sacculus and the sinus utriculi posterior. A t th e bend in th e root
there is an important collection of ganglion cells lying on the posterior aspect of the nerve, and from
this ganglion, in the adult, an intracranial communicating branch was found, going to the root of the
vagus. In th e 55 mm specimen this branch could not be satisfactorily traced. In the 63 mm Lepidotrigla
two branches arise from th e ganglion, one of which joins the root of the Vagus> the other one
entering th e intracranial vagus ganglion. The dorsal one of the two branches receives, on one side of