CRANIAL NERVES OF SILURUS AND MORMYRUS a0 
the lateralis fibers have reached the dorsal unpaired nucleus, 
another set of fibers runs dorsally and laterally to the gray 
substance above mentioned. It may be that these are vestib- 
ular fibers, though I do not consider it very probable. As a 
rule there is considerable difference between lateralis and vestib- 
ularis fibers, the former being more fine and compact, the latter 
in part coarser and in part a great deal finer. 
The nervus lateralis posterior is very large in Mormyrus. I 
cannot understand how Sanders (loc. cit., p. 53) was not impressed 
by its considerable size. 
While in Silurus the whole of it enters on the level of the 
glossopharyngeus (fig. 10), its entrance in Mormyrus extends as 
far backward as the second vagal root, as a result of the consider- - 
able backward enlargement of its corresponding lobe. Within 
the bulb the nerve runs some sections frontad and then sends a 
strong bundle of nerve fibers [fig. 19 and fig. 20 (3)] into the dorsal 
lobus lineae lateralis posterioris, occupying the same position as 
fibers of the nervus lateralis anterior, but caudally from them. 
These fibers also are covered by the double row of large cells 
of the crista (fig. 19). 
The relations as found in Mormyrus are very much in favor of 
Johnston’s*® conception concerning the relation between the 
lobus lineae lateralis and the cerebellum, which here resemble 
each other still more than in Silurus, for, in addition to the great 
resemblance between the molecular layer and the crista cere- 
bellaris, the relation between the Purkinje cells of the cerebellum 
and the large cells of the crista cerebellaris is more striking than 
in Silurus. 
I will again emphasize here that the fibers which Franz has 
described as facial fibers (loc. cit., Tafel 26, fig. 6) are fibers of 
the nervus lateralis posterior. 
Not all the fibers of the nervus lateralis posterior pass directly 
into the dorsal lobe. Some of them—be it by bifurcation or as 
separate tracts—run directly forward [fig. 20 (4)] after their 
entrance into the bulb. Piercing the coarse-fibered tract of the 
spino-cerebellar bundle (fig. 18), they end in the more ventral 
40 The brain of Petromyzon. Jour. Comp. Neur., vol. 12, 1902, p. 1. 
