THE NERVOUS SYSTEM OF A:\IPHIBIA 249 



dendritic processes. The structure of one of these cells, taken 

 from the most distal portion of the ganglion, is shown in figure 

 18. The proximal portion of the cell is not clearly seen in the 

 section figured, but the dendritic pole extends well out into 

 mesenchyme which surrounds the ganglion. In adjacent sec- 

 tions it can be followed as a delicate fibrillated strand of proto- 

 plasm about three times the extent of the process as shown in 

 the figure. The course of this fiber, however, is not directly 

 towards the skin and it becomes lost to view among the cells of 

 the mesenchyme. I have been unable to find in this stage of 

 the embryos any highly branched endings of naked fibers like 

 the terminals of the fibers of the giant ganglion cells of the trunk 

 (Paper I, figs. 17, 23 to 25). It may be that exceedingly fine 

 filaments of protoplasm from the ganglion cells reach the skin 

 here and there; Init if they do, they escape the most exhaustive 

 search through favorable preparations. The only perceptible 

 connection, therefore, of the ophthalmic ganglion with the skin 

 in the non-motile stage is through the areas of adhesion, or con- 

 tinuity with the ectoderm as described above. 



The attenuation of the ophthalmic ganglion caudad into a 

 slender root is illustrated in figures 1, 7 and 8 (G.oph.,R.oph.). 

 Caudally of the region indicated in figure 8 the root becomes 

 more slender still, so that it is very difficult to identify among 

 the mesenchyme cells. In frontal sections, however, it is easy 

 to trace the root to the brain in two closely associated divisions 

 which correspond to the two portions of the ganglion (figs. 11 

 and 12). As it nears the brain the root bends dorsad slightly 

 and approaches the brain in close association with the root of 

 the Gasserian ganglion l)ut at a slightly more ventral level than 

 the latter. 



As illustrated in figure 1, the Gasserian ganglion hes well out 

 from the brain with its long axis directed latero-ventrad. There 

 is at this time no perceptible development of fibers to form a 

 nerve trunk beyond the distal limits of this ganghon (fig. 1). 

 As in the case of the ophthalmic ganglion, there is here also an 

 area of adhesion between the ganglion and the skin. This con- 

 tact is at the distal end of the ganglion (fig. 9, Ad.G.G.). It is 



