106 JouRNAL oF COMPARATIVE NEUROLOGY. 
the spreading brush of such neurogliar processes and are there- 
by given support. 
9g. Summary of the Oblongata. 
The structural features of the oblongata of Mustelus may 
be homologized with those of the spinal cord to an unusual 
degree of clearness. 
The ventral cornu is represented by the nucleus of the VI 
nerve, and by the scattered commissural and tract-neurones of 
the formatio reticularis. 
The lobus vagi is, morphologically, the centre of the vis- 
cero-sensory system, but there has been afhnexed to it a com- 
plex of peripheral sense-organs. It has come to be, therefore, 
the centre for the entire communis system, components of the 
VII, IX, and X nerves. Endings are found related to neurones 
of the Golgi II type. These send their axones toward the 
viscero-motor nucleus. Fewer fibres of the system enter the 
fasciculus communis than in either the teleosts or the am- 
phibians. 
The viscero-motor nucleus is the representative of the 
paracentral nucleus. It is a morphologically continuous column 
of cells giving origin to the motor fibres of the V, VII, IX, 
and X nerves innervating viscera. The axones do not enter 
their nerve-roots directly, as a rule, but through the medium 
of the fasciculus longitudinalis dorsalis. Some appear to cross 
to the opposite side. Dendrites from the nucleus come into 
relation with axones of the lobus vagi. 
The general cutaneous nucleus is the homologue of the 
dorsal cornu. It is the primary centre for the general cutaneous 
components of the V, IX, and X nerves. The substantia gela- 
tinosa contains groups of small Golgi II neurones forming dense, 
_ felt-like tangles ; many terminal arborizations are found in these. 
Other terminations occur near larger neurones lying in the 
deeper parts of the nucleus. Many fibres of the system do not 
terminate in the nucleus, but are carried posteriorly as the 
spinal V tract for ultimate termination in the spinal cord. 
The tuberculum acusticum is a phylogenetically young 
