40 H. BERKELBACH VAN DER SPRENKEL 
having a very ventral position along the spinal V tract, with 
which it may be correlated, it is not surprising to find the motor 
cells in question lying along it. 
There is, however, a difference between Tinea and Silurus 
regarding their VII cells, in that, while in Tinca some of these 
cells still remain in the dorsal IX + X column, in Silurus all of 
them appear to have descended to form the fronto-ventral nucleus. 
The motor V nuclei in both fishes also are strikingly similar, 
not only by reason of their position, but also by reason of the fact 
that in both animals a division, or at least an obvious indication 
of a division, into two groups of cells is visible. 
We do not know what this division means. It seems probable 
that it is caused by the caudal shifting of the posterior cells of 
the nucleus, which may be more under the influence of the stimu- 
lation of the gustatory fibers that reach the nucleus from behind. 
This separation is also indicated in the root during its intra- 
meduallary course in Silurus, as seen in figure 4. 
The IX and X cells retain their dorsal position in the motor 
column of the vagus. 
The reduction of the eye-muscle nuclei in Silurus is interesting. 
The reduction of the visual apparatus and hypertrophy of taste 
in bottom feeders has also been emphasized by Herrick. The 
trochlearis root leaves the brain in a very frontal position, in this 
respect being only surpassed by Mormyrus. It is probable 
that the frontal entrance of the IV root in Silurus and Mormyrus 
are both due to the considerable development of the valvula. 
Mormyrus, which is no ‘taste fish’ at all (as an accurate examin- 
ation of its root fibers shows), exhibits entirely different relations 
of the V and VII nuclei. Both nuclei have kept a more dorsal 
position and they do not lie in the same region of the brain, so 
that there is nothing in favor of their place being defined by the 
Same system as in the other fishes mentioned. The V nucleus 
extends a little ventro-laterally in the direction of the reticular 
substance of its own sensory root, and the VII nucleus remains 
far dorsally. The latter has also a more frontal position. The 
less caudal, but especially the less ventral position, of the motor 
