418 JOHN BEAKD, 



Fig. 2. The right side of the apex of the cord shows six cells 

 taking on ganglionic characters. The cells of the spinal ganglia are in 

 course of migration. Embryo No. 135, 60 somites. Magnif. Leitz 2 mm, 



oc. 2 = 500 X I- 



Fig. 3. Portion of another section from the same embr3'0. An 

 earlier stage in the development of the transient ganglion-cells. The 

 central ones are still largely covered in by cells of the spinal ganglia. 

 One or two are in process of migration along with the latter. To the 

 left of the figure a nerve-process is seen passing out. Magnif. 500 X f- 



Fig. 4. From the same embrj^o as Fig. 2. Shows the migration 

 of ganglion-cells from the lips of the cord. To the left are two such 

 which have already wandered to the tip of the muscle plate. Magnif. 

 225 X I- 



Fig. 5. Is again intended to illustrate the early development of 

 the transient ganglion-cells. Four central ones are seen in the cord, 

 and among the cells of the spinal ganglia are three wandering transient 

 ganglion-cells. Pronephric region. Embryo No. 134, 54 — 55 somites, 

 5,25 mm. Magnif. Leitz 2 mm, 500 X f- 



Fig. 6. Shows the formation of a nerve chain by the application 

 of ganglion-cells end to end. Also transient cells wandering from the 

 cord. Embryo No. 141. Magnif. (Seibert, 4 mm) 225 X I- 



Fig. 7, 8, 9. Three consecutive sections from embrj^o No. 141. 

 To show the course and build of sub-epiblastic nerves formed by chains 

 of ganglion-cells, on each side of the body. Also their connection with 

 central ganglion-cells. Magnif. 225 X t- 



Fig. 10. From the same embryo. It shows more particularly a 

 transient ganglion-cell spinning a fibre over the muscle-plate. Magnif. 

 230 X |. 



Fig. 11. From embryo No. 141. The figure is very similar to 

 the preceding one. In addition it shows three central transient ganglion- 

 cells. Magnif. 225 X I- 



Fig. 12. A section from the same embryo, but ten sections further 

 forward. Five central ganglion-cells are depicted, of these three are in 

 the act of spinning nerve-processes. Magnif. (Seibeet 4 mm) 225 X ■§■• 



Fig. 13. In this figure, which is from the same embryo, a nerve- 

 process of a central ganglion-cell is shown passing between the myotome 

 and epiblast. Magnif. 500 X I- 



Fig. 14. A ganglion-cell resting on the tip of the myotome with 

 nerve-process spun to the centre in the spinal cord. Embryo No. 143, 

 10 mm, 86 somites. Magnif. 225 X I- 



Fig. 15. A section from the same embryo. The figure shows a 

 bipolar transient ganglion-cell which, by means of its nerve-processes, 

 bridges over the gap between the myotome and the spinal cord. Embr. 

 No. 143. Magnif. 500 X I- 



Fig. 16. Shows a ganglionic nerve-chain and wandering ganglion- 

 cells. The central cells are only becoming ganglionic. Embr. No. 143. 

 Magnif. as before. 



