Dec, lOK)] Profundus and Gasserian Ganglia in PI ethodon 31 



root (Rt. Prof. G). It is noticeable that the boundaries of the 

 profundus at this level are uneven and irregular. The outline 

 (Fig. 12) shows that the supra-orbital lateral line placode (PI.) 

 persists at this level, which is near the posterior end of the 

 optic vesicle (O. V.). 



Immediately posterior to the beginning of the root of the 

 profundus the Gasserian ganglion increases in size and 10 micra 

 posterior to the level of figure 12 it comes to he in contact 

 with the profundus. The profundus forms the dorso-mesial 

 portion of the ganglionic mass and the Gasserian the ventro- 

 lateral portion. Just posterior to this first contact with the 

 profundus the Gasserian enters the medulla by a large, cellular 

 root. (Fig. 13 Rt. Gass. G.) 



The Gasserian portion remaining consists of a small, tri- 

 angular mass in contact with the medulla and a larger rec- 

 tangular mass extending ventro-laterally to the region of the 

 first visceral pouch. As one reads posteriorly the ganglionic 

 mass dorsal to the gill pouch increases in size and comes to lie 

 as an irregular oblong near the supra-orbital placode and dorso- 

 lateral to the first gill pouch. It is connected by a narrow neck 

 with the proximal portion. The neck portion then drops out, 

 leaving the condition shown in Figures 15-16, where the two 

 parts of the ganglion are entirely separate. Only the larger 

 portion (Fig. 15, Gass. G.) is figured in detail. Its close 

 relation w4th the first visceral pouch (Ph. P. I) is shown in the 

 outline (Fig. 10) while the detail drawing (Fig. 15) shows its 

 slight lateral contact with the supra-orbital lateral line placode 

 (PI). At its ventro-lateral border the ganglion is irregular 

 in outline and is at one point in close contact with the ectoderm 

 just ventral to the placode. At its extreme ventro-lateral edge 

 the ganglion comes into contact with the ectoderm of the first 

 visceral pouch (Ph. P. I). 



Slightly posterior to this level the proximal portion of the 

 Gasserian drops out, leaving only the part over the gill pocket. 

 At this same level a few nuclei of the dorsal lateralis ganglion 

 on VII appear as a loose mass dorso-lateral to the Gasserian 

 (not figured). The dorsal lateralis ganglion of VII is ver}' near 

 the ectoderm and dorsal to the gill pouch. It retains this 

 position for several sections. The Gasserian becomes gradually 

 smaller and more vaguely marked out and drops out just 

 posterior to Fig. 15. 



