554 DAVIDSON BLACK 
importance corresponds to that of the jaw musculature which 
in this form is exceedingly well developed. 
A comparison of the reconstruction charts brings out the addi- 
tional fact that the independence of the rostro-dorsal motor V 
nucleus from the caudo-ventral moiety varies directly with the 
development of the visual apparatus, being greatest in Lophius 
and the Pleuronectidae and least in Ameiurus and Tinea. 
Further, this independence of the cell groups of the motor V 
nucleus varies indirectly with the development of the gusta- 
tory apparatus, being greatest in Lophius and the Pleuronec- 
tidae, where the secondary ascending gustatory tract is relatively 
small, and least in Ameiurus and Tinca, in which this system is 
highly developed. In regard to the functional development of 
the neurone systems contrasted above, Gadus occupies an inter- 
mediate place, a condition which is accurately reflected in the 
arrangement of the elements of the motor V nucleus in this 
form. 
‘Though many further examples might be cited of the variations 
of the moieties of the motor V nucleus in conformity to periph- 
eral development, especially when the relations of this nucleus 
are compared to this end among the Pleuronectidae, sufficient 
has been said to indicate that the dorsal group of motor tri- 
geminal elements is most probably concerned in the innervation 
of the musculature of the jaw, while the ventral group fune- 
tionates chiefly in the supply of the trigeminal opercular muscles. 
Oculomotor and trochlear nuclei and roots (Nu. et rad. Nn. III 
et IV). The peculiar and complex relations of the emergent 
trochlear root fibers have already been discussed in connection 
with the description of this nerve in Solea. However, the posi- 
tion, make up and mutual relations of the oculomotor and 
trochlear nuclei among teleosts present certain points of in- 
terest and will require some further consideration here. 
Kappers has already pointed out that the oculomotor nucleus 
as a general rule occupies a more rostral position among tele- 
osts than among selachians and broadly speaking this teleostean 
characteristic may be correlated with the increased relative im- 
portance of the tectum opticum and its efferent pathways among 
