MOTOR NUCLEI IN PHYLOGENY DAT 
looked for among lower vertebrates as muscles distinct from one 
another, though closely associated and synergic in their action. 
Among elasmobranchs the well developed trapezius is wholly 
a specialized visceral muscle, but it is closely associated in its 
action with somatic muscles innervated by cervical motor nerves. 
It would thus appear that in these animals a prostadium of the 
cucularis complex might be recognized in these two distinct 
though synergic sets of muscles. 
In teleosts, however, the elements of the trapezius musculature 
have necessarily been much reduced owing to the development 
of the bony operculum. It is probably on this account that both 
components of the cucularis complex of higher forms are ap- 
parently never represented in one individual among bony fishes, 
but either the visceral element (e.g., Ameiurus, Lophius) or the 
somatic element (e.g., Gadus) is alone retained. In either case, 
however, this levator musculature of the shoulder girdle in these 
forms would appear to be homologous with one or other of the 
components of the cucularis complex of mammals. 
This concept accords well with the facts of embryology and 
is in harmony with the further phylogenetic history of the acces- 
sory nucleus, as well as with its ontogenetic history in mammals. 
Motor facialis and glossopharyngeal nuclei and roots (Nu. et rad. 
mot. Nn. VII and IX). In contrast to the condition obtaining 
in ganoids and selachians, among all teleosts thus far examined a 
large portion of the VII motor nucleus is separated from the 
caudal viscero-motor column and lies more ventrally than the 
latter in the tegmentum. This sequestration of motor facial 
elements may affect the whole nucleus (e.g., Silurus, Ameiurus, 
Lophius), or only its rostral portion (e.g., Tinea, Pleuronectidae). 
The relations of the motor LX nucleus to the other constituents 
of the more primitive caudal viscero-motor column are also 
highly variable among the different species of teleosts. Thus, 
the motor IX nucleus together with the elements of the caudal 
motor VII nucleus may be in direct continuity with the motor 
X nucleus (e.g., Tinea, Pleuronectidae), or the motor IX nucleus 
alone may form the rostral end of the motor vagus column 
(e.g., Silurus, Ameiurus). Further, the motor IX nucleus may 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 27, NO. 4 
