472 L. S. STONE 



When the operation is done at about stage 26 and an area is 

 removed as shown in figure 62, about twelve hours after operation, 

 no postauditory primordia of the lateral-Hne sense organs appear. 

 Only lateral-Une sense organs anterior to the ear may be found. 

 The extent of the blue area is marked out by dotted line (fig. 63) . 



An examination of certain typical specimens in this type of 

 operation does not show such an extensive lack of ganghonic 

 material as found in the regions of V and VII when all the crest 

 cells are present. 



The case illustrated in figure 63 shows normal branchial arches 

 (fig. 64) and certain small ganglionic masses of IX and X. There 

 is a very small X visceral ganglion (fig. 65). There are no first 

 nor second branchial trunks. From the poster o ventral portion 

 of this ganglion a slender trunk comparable to the visceral trunk 

 of the vagus passes posteroventrally alongside of a branchial 

 blood vessel behind the anlage of the branchial bars to the poste- 

 rior portion of the pharynx where its fibers are lost against the 

 side of a blood vessel. There are no lateralis fibers in the visceral 

 trunk because there are no lateral-line ganglia in the IX or X 

 complex. A small visceral ganghon of IX lies below the level of 

 X \'isceral ganglion at a lower level than on the normal side. 

 Through it pass a few motor fibers which are given off to branchial 

 muscles. A slender branchial trunk passes to the lateral side 

 of the anlage of the levator arcus branchialis primus muscle to 

 which it appears to give off a few motor fibers. Here it is lost 

 in the first branchial arch and gives no evidence of containing 

 sensory fibers. No special visceral fibers pass anteriorly toward 

 the pharyngeal region. 



Another specimen killed eighteen days after operation shows 

 a few poorly developed sense organs in the occipital region which 

 are supplied by a few nerve fibers from a very small IX lateral- 

 line ganglion (fig. 66) . A few lateralis fibers come from a small X 

 lateral-line ganglion to innervate the posterior sense organs of the 

 occipital group. The visceral ganglion of the vagus is somewhat 

 smaller than on the normal side and gives off a visceral trunk 

 which passes through a small ganglion on the median side of the 

 fourth branchial arch. This ganghon seems to be a portion of 



