1424 
On the level of the V. entrance, quite dorso-laterally, a group of 
very large cells can be seen, the nucleus octavo-motorius frontalis 
of Kappurs'), also described by Jonnston as “spindle-cell nucleus.” 
From these large cells the nearites go out in a ventral and also in 
a frontal direction to the mid-brain, where they cross the raphe 
close under the III nuclei. Collaterals of these seem to go, in my 
opinion, also to the environs of the [II nuclei from the same side. 
There is much in favour of Karpers’ theory that these large cells 
are the homologa, or at least the analoga, of the front portion of the 
nucleus Deiters or Becutrrews nucleus of the higher animals. For 
in reptiles one still finds the ne. Deiters grouped into two portions, 
each of which for a great part gives origin, the one to a tractus Deiters 
ascendens, the other to a tractus Deiters descendens. In this respect they 
show much similarity with the separated ne. octavo-mot. anterior and 
posterior (Karpers). In some of the lower mammals (Marsupials) 
something of this separation is still visible. 
Those large cells of Petromyzon, which lie on the border of the 
cerebellum, form with their neurones still the only certain connection 
of these regions with the base of the brain. Cells lying immediately 
medially and dorsally therefrom and of a smaller type, also send 
neurones ventrally and, what is of importance, also frontally, hereby 
thus forming a system of frontally running fibrae arcuatae. 
Whether these smaller cells, or some of the large ones, give rise 
to those fibres which Scuinuinc has called homologous to the 
brachium conjunctivium, I do not venture to decide. I consider it, 
however, most probable that from this lateral group of reflex cells, 
large, small, or both, the development of the nuclei cerebelli of the 
higher vertebrates proceeds, and that this takes the way as indi- 
cated in Selachians, where the primitive nucleus lateralis cerebelli 
also lies on the level of the entrance of the trigeminus root, laterally 
from the ventricle. 
Selachians. 
In Selachians (sharks) Karpers ®) has described a cellgroup as nucleus 
lateralis cerebelli. Regarding this nucleus nothing but its position 
has been given. 
It now appears to me that in all probability this is the forerunner 
of the nuclei cerebelli of the higher vertebrates. 
1) Arns Karpers, The structure of the Teleostean and Selachian Brain. Journal 
of Comp-Neurol. Vol. 16, 1906. 
2) KAPPERS, l. c. 
