ORIGIN OF JAW APPARATUS aot 
has thus been but slight displacement of the root portions of 
these nerves caudad. The septal nerve, while largely devoted 
to the sensory innervation of the snout, frequently sends one or 
two branches to the anterior end of the jaw apparatus. 
The innervation of the jaw apparatus is quite sharply limited 
posteriorly. There is thus a section of the central nervous system 
Fig. 11 Front view of velar disk of Amphioxus with the dorsal six of the velar 
tentacles projecting into the buccal cavity. When the lower six are thrust for- 
ward the lip fold disappears. 
lying in front of the jaw apparatus whose peripheral nerves do 
not typically invade the jaw territory and another section of 
the central nervous system whose nerves supply territory nor- 
mally behind the jaw apparatus; between these two lies a section 
of the central nerve cord which, to judge by the five nerves it 
sends out, is devoted exclusively to the control of the jaw appara- 
tus. In the peripheral reaches of its nerves is built up a plexi- 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 33, NO. 4 
