586 'Journal of Comparative Neurology and Psychology. 



contraction of the adjacent myotomes and might not the impulses 

 sent in by them serve to bring about inhibition on the one side 

 and the contraction of the corresponding myotomes of the opposite 

 side ? 



THE VISCERAL SENSORY COMPONENTS. 



These components can be treated best by describing the sensory 

 portions of the IX and VII nerves. The X nerve need not be 

 described, since its branchial divisions after they leave the epi- 

 branchial trunk (see 1905 paper) are like the IX in every way. 

 The last two divisions of the vagus have not been studied in these 

 preparations. 



The roots of the IX nerve emerge from the cranium just behind 

 the auditory capsule and enter the "ganglion. Beyond the gan- 

 glion the sensory and motor fibers cannot be distinguished until 

 they reach their destinations. The trunk descends over the first 

 gill sac and enters the first branchial arch. Here it descends mesal 

 to the branchial cartilage (figs, i to 3) and gives off a visceral 

 sensory ramus mesad (figs. 4 to 6). The visceral ramus reaches 

 the wall of the water tube somewhat above its middle and divides 

 into dorsal and ventral branches. The dorsal branch runs up in 

 the wall of the water tube to its dorsal surface where it forms a 

 rich ramification (fig. 16) extending forward in the roof of the 

 water tube to the velum. In fig. 16 it is seen that the water tube 

 is much wider opposite the gill bars than between the gill pouches 

 and this accounts for the arrangement of the fibers. Some of the 

 fibers of this branch do not stop in the roof of the water tube but 

 pass on up to the wall of the oesophagus. A special bundle of 

 such fibers is marked o.b. in fig. 16 and its continuation is shown 

 in fig. 17, where it ramifies in the wall of the oesophagus. Fig. 16 

 is taken from the same section as fig. 6, where this same bundle 

 is indicated {o.b.). These endings in the wall of the water tube 

 and of the oesophagus are slender simple fibers or bunches of 

 fine fibers branching out from a small knot or varicosity. Many 

 of the fibers are so excessively fine that they could not be drawn 

 at this magnification. 



The ventral branch of the ramus visceralis descends in the wall 

 of the water tube and ramifies in its floor (fig. 18). Here again 

 very many of the finest fibers are omitted from the drawing. 

 Taste organs are present as in P. dorsatus but are not well impreg- 

 nated. 



