260 G. E. COGHILL 



degree of separation of these two ganj2;lia is somewhat exaggerated 

 in figure 2. Ganghon a is distinctly farther advanced in develop- 

 ment than ganglion b. In horizontal sections it exhibits a line 

 of cleavage between two portions, and each portion gives rise to 

 a distinct fiber bundle. These two bundles emerge from the 

 distal end of the ganglion and obviously represent the r. oph- 

 thalmicus superficialis VII and the r, buccahs VII. The latter 

 is directed the more ventrad. There are now sheath cells upon 

 the fiber bundle from the ganglion to the lateral line primordium, 

 and closely attached to the latter the naked fibers extend for 

 some distance in two strands, representing the two nerves as 

 indicated. The primordia of the lateral lines have shifted farther 

 rostrad relative to the position of the auditory vesicle, from 

 which they have become completely detached (Paper I, fig, 57, 

 Pr.LL) Their position, also, is somewhat more dorsal. Their 

 ventral projection is distinctly larger and shows a tendency to 

 form into two divisions. 



Ganglion b, of the hyomandibular division, is still very imper- 

 fectly differentiated in its proximal portion from the auditory 

 ganglion. Distally it is seen in frontal sections along the caudal 

 and lateral border of the geniculate ganglion (fig. 2, G.gen.), 

 the point of it extending ventrad behind the attachment of the 

 entoderm of the spiracular pouch to the ectoderm. From this 

 point of the ganglion a few^ fibers extend on ventrad and into 

 the primordium of the hyoid arch. These fibers can be recog- 

 nized only as they run in the plane of section. The fact that 

 these fibers have no perceptible connection with the skin and 

 that the primordium of the mandibular lateral line has not yet 

 appeared leads me to interpret them as probably motor. 



The root fibers of the lateral line ganglia still enter the brain 

 at a slightly more rostral level than the auditory vesicle, and in 

 two divisions (figs. 23 to 28, R.L.L.VII,a and b). The dorsal 

 division seems to arise from ganglion a; the ventral division, 

 from ganglion b. In figure 23 a few ascending fibers of each 

 division can be seen {L.L.VII,Asc.,a,b). In figure 28 the corre- 

 sponding descending divisions of these root fibers are repre- 

 sented {L.L.VII,Des., a and b). Presumably the fibers bifurcate 



