314 G. E. COGHILL 



Fig. 15 is 60 fi still farther caudad, showing the Gasserian ganglion {G.G.) con- 

 nected by a slender root with the root mass (R.M.) at the surface of ther brain, 

 and the relation of this ganglion to the lateral line primordium {Siip.L.L.). 



Fig. 16 Early flexure stage (No. 550, section 1-2-14). X 50. This figure is 

 introduced to show the plane of section of figure 22, which is taken from the same 

 section. 



Fig. 17 Coiled-reaction stage (No. 561, section 1-3-14). X 50. This figure 

 is introduced to show the plane of section of figure 33, which was taken from the 

 region indicated between the lines at c. 



Fig. 18 Early flexure stage I'No. 545, section 5-2-14). X 500. A ganglion 

 cell with its peripheral, dendritic process, in the distal portion of the ophthalmic 

 ganglion. The spherules in the cytoplasm are yolk. 



Fig. 19 Early flexure stage (No. 593, section 2-5-7). X 500. Ganglion cells 

 of the Gasserian ganglion, with axones reaching towards the brain. Other indif- 

 ferent cells appear around the ganglion cells. The yolk is indicated in the cyto- 

 plasm as in the last figure. 



Figs. 20 and 21 Non-motile stage transverse section (No. 543, sections 3-3-16 

 and 13, respectively). X 500. 



Fig. 20 is 15 M caudad of figure 21, and shows root fibers of the trigeminal 

 nerve within the brain {Tr.Des.V). Both figures show cells of the root mass 

 (R.M.) Fig. 21 a large cell [D.C.) which has the anatomical features of Rohon- 

 Beard cells of the spinal cord sends a process out of the brain into the trigeminal 

 root. A similar cell [D.C.) appears in figure 20, in which figure the motor nucleus 

 of the trigeminus (Nuc. vis.m.) is seen to be in a much more ventral position. 



