296 IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
I 
more columnar posterior saccular portion. The auditory fibers 
enter the brain in a compact root just posterior and ventral to 
the lateral line roots. 
The geniculate or visceral VII ganglion is a triangular mass 
quite distinct from the rest, in contact caudally with the pos- 
terior lateral line ganglion. The roots of the YII-VIII complex 
are, from anterior to posterior : . (1) the large ventral lateral 
line root, (2) a visceral root soon separating into a distinct 
dorsal communis and a ventral motor root, (3) the dorsal lateral 
liiie root, (4) most posteriorly, the large auditory root. These 
do not follow each other in succession, but overlap to a large 
extent so that lateral line, communis, visceral motor, and audi- 
tory fibers may be seen leaving the brain in a single section. 
The IXth nerve contains visceral sensory, visceral motor and 
lateral line components. It rises from the wall of the medulla 
by a series of five roots. The first three are small motor roots, 
extending in an attenuated tract much farther anteriorly than 
the main root which is largely visceral sensory. The lateral line 
root is a small distinct tract entering the brain just ventral to 
the lateral line root of X. The ganglion lies at the end of a 
long root, in a cavity of the cartilage of the ear capsule. The 
visceral ganglion forms a large oval enlargement on the nerve. 
The lateral line ganglion is a small mass of cells beginning some- 
what anterior to the visceral ganglion. Though lying close 
to the latter, it is perfectly distinct from it, and its presence is 
indicated by an appreciable indentation in cross-section. 
The vagus nerve contains visceral sensory, visceral motor, gen- 
eral cutaneous and lateral line components. The last two are 
distributed through supra-temporal and auricular rami to the 
canal organs of the posterior head regions and through a large 
lateralis trunk to the canal organs of the body. The lateral 
line fibers rise in one large compact root just dorsal and ex- 
tending slightly posterior to the lateral line root of IX. They 
pass posteriorly in a flat ribbonlike band closely appressed to 
the brain wall. The lateral line ganglion shows evidence of seg- 
mentation into three parts. The first is the most anterior part 
of the vagal ganglion, a slender column of cells which gives rise 
to the supra-temporal ramus. Just posterior to this and for some 
distance in contact with it lies the major part of the ganglion, 
two scarcely separable masses of cells from the first of which 
