THE NERVOUS SYSTEM OF AMPHIBIA 267 



ganglion. This incipient root, however, does not reach the brain 

 (fig. 1, G. Jug.). 



3. The visceral sensory component. The visceral ganglion of 

 the glossopharyngeus fuses with the ectodermal thickening which 

 rests upon the entoderm of the first branchial pouch (Paper I, 

 fig. 56, Ec.Th.). This structure is obviously the epibranchial 

 placode of the glossopharyngeus. From it a strand of ganglion 

 cells follows along the lateral line root to the brain. No definite 

 relation of root fibers, however, can be made out (fig. 1, G. Vis. IX). 



The visceral ganghon of the vagus nerve is in a still more 

 embryonic condition. It consists for the most part of a loose 

 collection of cells situated on the ventral side of the lateral line 

 and general cutaneous gangha. The most highly different iated 

 part of it reaches out to the ectodermal thickening over the second 

 branchial pouch, with which it fuses. Farther caudad there is 

 loose connection of the ganglion with the ectodermal thickening 

 over the third and fourth visceral pouches. The ganglion at this 

 time has no root connection with the brain (fig. 1, G.Vis.X). 



B. THE EARLY FLEXURE STAGE 



1. The lateral line component. The lateral line primordium, 

 which is situated over the first branchial pouch, has become 

 elongated dorso-vent rally, and two other primordia appear, the 

 one situated over the second branchial pouch ojiposite the first 

 myotome and the other opposite the second to fifth myotomes 

 (Paper I, fig. 57). 



The lateral line ganglion on the ninth nerve has now become 

 spindle form, but it still reaches to the primordium (fig. 2, 

 G.L.L.IX). Its root fibers reach the brain in close contact with 

 the root fibers from the lateral line ganghon on the vagus. The 

 latter ganglion now sends out a projection of cells which reaches 

 to the primordium which is situated over the second branchial 

 pouch, and extends caudad to the primordium of the trunk 

 (fig. 2). 



The roots of these postauditory lateral line ganglia approach 

 the brain together (figs. 29 and 30). In figure 30 this root 



