98 GEORGE W. BARTELMEZ 
which, caudal to Mauthner’s cell, is separated from the rest of 
the fasciculus longitudinalis medialis by the internal arcuate 
decussation. Wallenberg (’07) has termed this bundle ‘fascicu- 
lus octavo-motorius,’ but the term is hardly justified, as it should 
include only the coarse fibers of this bundle, the fine ones having 
descended from the mesencephalic (and diencephalic?) tegmen- 
tum. Moreover, all the ‘octavo-motorius’ fibers are not included 
within it, and the axones of the Miller cells of the partes suprema 
et superior are as much concerned with the cerebello-bulbar and 
cerebello-spinal systems as with the octavus (p. 95). 
The homologizing of these cells with the Miller cells of cyclo-- 
stomes, as Edinger has done, possibly requires further evidence, 
though the observations of Johnston (’02), Edinger (’08) and 
others leave little room for doubt that in cyclostomes the cells 
which give rise to the Miillerian fibers are merely the largest ele- 
ments of the nucleus motorius tegmenti. Their position between 
their tract, the fasciculus longitudinalis medialis, and the visceral 
motor nuclei is the same in all Ichthyopsida; more important are 
the facts that in the cyclostomes, ganoids and teleosts the bulbar 
cells are confined to the acoustico-lateral levels and most of the 
axones descend. Johnston (’02) counted from twenty to twenty- 
four giant fibers at the caudal end of the bulb in Petromyzon, 
although there were but seventeen or eighteen Miller cells in 
that region of the brain. The others presumably came from the 
mesencephalon. There are from twenty-five to twenty-seven bul- 
bar Miller cells in Ameiurus and at the caudal end of the oblon- 
gata their axones are the giant fibers, since the mesencephalic 
fibers are reduced in caliber at this level. It should be said at 
this point that Johnston found an additional pair of cells larger 
than all the others just behind the motor VIIth roots. That 
these are homologous with Mauthner’s cells there can be little 
doubt, as will appear below. The similarities in relations, 
receptive fields and: internal structure between the ordinary 
cells of the motor tegmental nucleus, the Miiller cells and the 
pair of Mauthner’s cells will be discussed under the head of 
Mauthner’s cell. 
