The brain of Acipenser. 83 
the internal surface of the cerebellar crest and enter the ventro- 
mesial angle of this lobe, breaking up in it as do the fibres of the 
dorsal root. It is possible that some fibres of the lateral line X 
enter this lobe in the same way. The neurites of cells in the lobus 
which run ventrad around the internal surface of the cerebellar 
crest run with these lateral line fibres, and together they constitute 
the conspicuous bundle of fibres connecting the lobus lineae lateralis 
with the acusticum, shown in GORONOWITSCH’s fig. 53 and in my 
Phot. 3. Near the cephalic end of the lobus there is in the same 
situation a large bundle of fine fibres which come from the dorsal 
surface of the cerebellar crest and pass to the base of the medulla. 
I shall discuss the significance of these fibres in a later section 
(page 190 ff.). 
6) Visceral and end-bud center. 
The sensory roots of the VII, IX and X cranial nerves, ex- 
clusive of spinal V components and of the lateral line nerves which 
have often been assigned to the VII and X nerves, enter one common 
center in the medulla which in Ganoids and Selachians has been 
known as the lobus vagi, and in Teleosts has been described as two 
structures under the names of lobus vagi and lobus trigemini or 
lobus impar. I shall describe it under the name of lobus vagi, 
pending the discussion of its homologies in other Vertebrates. 
In frontal sections of the cephalic part of the spinal cord of 
Acipenser, stained with haematoxylin, there is seen in the dorsal 
raphe a bundle of fine non-medullated fibres which is laterally com- 
pressed between the dorsal tracts. Close examination brings to light 
two or three very small bundles at either side of the dorsal raphe 
and imbedded in the dorsal part of the reticular substance sur- 
rounding the central canal (Fig. B, E). Following these forward, 
both lateral and median bundles are found to increase in size and 
to come together into a common bundle above and at the sides of 
the central canal as it rises toward the dorsal surface to open out 
in the IV ventricle (Fig. B, B). Farther forward (Fig. B, A) the bundle 
grows larger and commissural fibres appear, crossing above the 
central canal. Meantime the medullated fibres of the dorsal tracts 
have been pushed outward at either side, and are very sharply 
distinct from the bundle of fine fibres. Among the fibres of the 
median bundle and the commissure are a number of cells which 
appear to be nervous in character. In front of the commissure the 
6* 
