8 H. BERKELBACH VAN DER SPRENKEL 
of small irregularities. In order to indicate to which nuclei the 
roots correspond, the same markings are used as in Kappers’ 
diagrams. 
In figure 4 the exact place of entrance—not merely the level 
of each root is projected, together with its central course. Of 
the latter, only the most important points were projected, these 
being connected by rather smooth lines. 
These three projections are intended to show the natural 
forms and positions of the nuclei and roots in the medulla and 
basis mesencephali in the most painstaking way. The differences 
between these projections and Kappers’ diagrams lie chiefly in 
the fact that Kappers draws each nucleus as it appears when 
projected on its own radial, the center of the radius being the 
middle of the bottom of the [Vth ventricle, whereas I projected all 
the nuclei on the medial plane of the raphé. From this it results 
that the place of the V and VII nuclei is less ventral in my pro- 
jection than in Kappers’ diagram. Moreover, Kappers does not 
aim to show the exact form of the nuclei, but only the spaces 
within which they are found. 
SILURUS GLANIS 
The eye-muscle nerves in Silurus are poorly developed, in 
conformity with the life habits of this animal which belongs to 
the bottom-feeders, living in the mud and searching for their 
food chiefly by exploring the bottom with their taste organs. 
This is in contrast to the plankton feeders, which swim around 
near the surface and seek their food chiefly with their visual 
apparatus. 
The oculomotor nerve is, consequently, relatively thin. Ap- 
proaching the mesencephalon in the cleft between the inferior 
lobes and the base of the midbrain, it pierces through the base in a 
caudo-frontal direction (fig. 4). As figure 2 shows, the nucleus 
lies several sections in front of the entrance of the root, its caudal 
part being the larger. The cells are located near the raphé, 
but it is not an unpaired nucleus in the strict sense, since there is 
clearly a small region devoid of cells between the left and the 
right nucleus. The dorso-ventral and transverse diameters of 
