CRANIAL NERVES OF SILURUS AND MORMYRUS if 
tract it is closely followed by the sensory root, which remains 
dorsally of these gustatory fibers (figs. 6, 7 and 8). 
More caudally—behind the place where the secondary fibers 
from the sensory VII nucleus that constitute the larger part of 
the anterior secondary gustatory tract have disappeared from the 
sections—the descending sensory V acquires a more medial 
position, but only for a short distance, because it is soon pushed 
more laterally again, and especially more dorsally (fig. 10), 
by the communis nucleus of the [X and X.?° 
In the region of the X the descending V receives a considerable 
_ bundle of root fibers from the second sensory X root, which are 
doubtless the somatic sensory fibers of that nerve which have 
been described by C. J. Herrick. 
Where the oblongata passes over into the spinal cord, the de- 
scending V gradually disappears in the posterior horn of the 
cervical gray, which thus constitutes a correlation center for the 
sensibility of the skin of the head and the front part of the body. 
The motor VII root (figs. 4 and 6) directly after its entrance 
passes through the anterior secondary gustatory tract (fig. 7) 
as a strong coarse fibered tract, runs to the floor of the fourth 
ventricle through some strong bundles of the fibrae arcuatae 
internae, curves in a caudal direction (frontal knee-bend), and pro- 
ceeds backward in a horizontal course laterally from the fasciculus 
longitudinalis posterior and Mauthner’s fiber (fig. 8). Directly 
behind the frontal pole of the VII nucleus its fibers descend and 
diverge as indicated in figures 4 and 8. 
It is very interesting that a more caudal course of motor VII 
fibers (fig. 4) to the dorsal cell column of the [X and X, as occurs 
in most teleosts, cannot be traced in Silurus. 
This absence of a caudal VII root is the more interesting since 
in Tinea this caudal root is already considerably diminished in 
comparison with the Pleuronectidae (Hippoglossus, Rhombus, 
Pleuronectes). The same process of frontal, and _ especially 
ventral migration of the motor VII cells to the region of the 
° It seems strange to me that, while the sensory V has a relatively more ventral 
position in Mormyrus than in Silurus, the sensory communis roots in Silurus 
run dorsal to that tract while in Mormyrus they run ventrally of it. 
