354 HOWARD AYERS 
length of the jaw bar near the base of the tentacles made up 
of the larger nerve branches given off from the five jaw nerves. 
A satisfactory analysis of this longitudinal trunk, its components 
and the relations of the plexiform structures to it has not been 
Fig. 8 Dorsal view of velum, velar tentacles and chamber, and anterior end 
of gill basket of Amphioxus. Six of the velar tentacles are protruded into the 
buccal cavity. The attachment of the velar ligaments is shown on the left side. 
The insertion of three myotomes is seen on the left side. 
published. One or more branches of the longitudinal trunk 
run out into each tentacle. Thus the ventral branches of five 
pairs of segmental nerves of unmodified spinal type supply the 
jaw apparatus and exercise control of the whole mechanism 
