CRANIAL NERVES OF SILURUS AND MORMYRUS 31 
other fishes by Herrick in Menidia** and by Kappers in several 
other teleosts.*® 
The cells of the motor VII nucleus are larger than those of 
the eye-muscle nuclei and smaller than the adjacent reticular 
cells (fig. 16). The nucleus lies in the upper third part of the 
bulb and is separated from the floor of the ventricle only by the 
fasciculus longitudinalis posterior and the dorsal arcuate fibers 
(figs: 16;,.17): 
In the caudal direction the number of cells in the median 
line diminishes, while some lateral cells are added. In the most 
caudal sections the cells acquire a somewhat larger size and take 
a somewhat less deep stain. Some of them have come to lie 
next to the fasciculus longitudinalis posterior. It is difficult 
to define the exact caudal limit of the VII nucleus. It is very 
obvious that the chief VII nucleus in Mormyrus has a much more 
dorsal and also a more frontal position than in Silurus. The 
more frontal position may be partly due to the strange develop- 
ment of the dorsal arcuate fibers behind it, together with the small 
size of the taste nucleus. The lack of ventral migration is cer- 
tainly due to the absence or small size of the secondary gustatory 
tracts In comparison with Silurus. 
The posterior part of the VII nucleus, connected with the 
IX + X nucleus, extends some distance in the ventral direction 
(see the diagram, fig. 21). 
As could be predicted from the small size of the III and IV 
nerves, the abducens nerves are very small. Only few fibers could 
be found leaving the ventral region of the bulb, about at the level 
of figure 17, in a frontal direction. The nucleus could not be 
delimited with certainty. 
The sensory IX root has been mentioned already when dealing 
with the sensory VII, and it has been stated that in its caudal 
course before entering its nucleus it fuses with the sensory VII 
root (fig. 18). The root leaves the frontal pole of the communis 
3 Jour. Comp. Neur., vol. 9, 1899. 
36 Weitere Mitteilungen itiber Neurobiotaxis. no. VIII. Ueber den motorischen 
Glossopharyngeus und Facialis bei niederen Vertebraten. Folia Neurobiologica, 
Bd. 8, 1914, p. 383. 
