1427 
4th ventricle and in the basis of it, fig. 5, we must consider for 
the present as standing in no relation to the ne. cerebelli. They are 
probably reticular elements (perhaps the forerunners of the ne. loci 
cerulei of the higher vertebrates). 
If now we examine the nucleus cerebelli in its topographic 
conditions, it appears that it lies in that part of the cerebellum 
which passes over into the oblongata, (fig. 4 represents a frontal 
section through the greatest breadth of the nucleus), and that its 
cells border immediately on the cells of the area vestibulo-lateralis, 
only few of which are still to be seen in fig. 4, but which are to 
be seen better in fig. 3 (the boundary of the crista cerebellaris 
indicates in both figures approximately the boundary between VIII 
and V regions.) 
P 
ne reticul 
Fig. 5. Selache maxima. 
In this drawing a lateral group of cells is to be seen in the VIII 
area (fig. 30.¢.) which have a different axial position than the cells of 
the more medially situated group. They seem to be a very ventral 
continuation of the nucleus cerebelli. From there too arcuate-fibres 
go out, which run very peripherally in the oblongata. 
92 
Proceedings Royal Acad. Amsterdam. Vol. XVIII. 
