MAUTHNER’S CELL 95 
the pre-mauthnerian group (P.Pre M.) is closer to Mauthner’s 
cell, while the post-mauthnerian group (P. Post M.) is separated 
from it by a distinct interval. In some brains, in fact, the most 
caudal cells of the former group are found in the same transverse 
sections as the body of Mauthner’s cell. The Miiller cells of the 
post-mauthnerian groups are distinctive, but’ the other cells dif- 
fer from those of more caudal levels only in that there are more 
and larger dendritic branchings in the ventro-lateral than in the 
ventro-medial field, as appears in figure 4. The cells of the pre- 
mauthnerian group are large, like those of the pars superior and 
pars suprema; it has about a dozen cells as large as the largest 
Miller cells of lower levels. Here too we find the densest neuro- 
pil ventro-laterally. 
The two most rostral groups, pars superior and pars suprema, 
lie at the upper end of the acoustico-lateral decussation, with 
which they are intimately connected; and through the lemniscus 
lateralis they connect with all levels of the dorsal acoustic nucleus. 
At this level the fasciculus longitudinalis medialis and lemniscus 
are turning laterally and the cells of the nuclei of the motor teg- 
mentum are also more lateral, so that most of them lie just ven- 
tral to the lemniscus. Like all other groups, they are closely 
related, to both of these tracts. Both groups have another im- 
portant connection: most of the fibers of the cerebello-tegmental 
tracts end in them. The direct cerebello-tegmental tract cannot 
be traced much farther caudally than the pars superior, and the 
pars suprema may be looked upon as the chief end-station of 
this system. The more caudal cerebellar system, which is re- 
layed in what Tello has described as the preventricular tegmental 
nucleus, makes connections with the peri-mauthnerian groups, as 
well as with the pars superior. This system will be discussed at 
greater length in the paper on the acoustic nuclei. The pars 
superior is more intimately related to it than to the direct cere- 
_bellar path. The pars superior. differs from the pars suprema 
also in that it, like the pre-mauthnerian group, is closely related 
to the nucleus princeps trigemini. Both of these groups have 
their dendritic fields farther laterally than the more caudal groups, 
and their dendrites extend somewhat rostrally as well; this con- 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL, 25, No. 1 
