580 Stewart Paton 



a Fibrils passing beyond cell in direction of central canal, e Fibril 

 Coming from cell b unites with one from cell d. (Same magnification 

 as Fig. 1.) 



Fig. 6. Torpedo ocellata length 6 mm. I. Cell from ventro-lateral portion of 

 spinal cord, a Fibril may be traced in unbroken continuity from cell 

 process into bündle running in direction of h. IL Ventral roots — 

 same section. (Zeiss apochrom. obj. 2 mm. oc. 12.) 



Fig. 7. Scyllium eanicula length 8 mm. At this stage neurofibrils may be 

 Seen threading their way among the nuclei, which are now a con- 

 stituent part of the bridge. At -E" is a small part of commissural tract. 



Fig. 8. Torpedo ocellata length 6 mm. Within the protoplasm of the bridges 

 (B, bundles of fibrils some of which are surrounded by envelopes 

 that are continuous with the process of certain cells [h). Frequently 

 the fibrils as they approach the nuclei spread out in a brush-like 

 arrangement, and others (c) skirt the edge of these structures as they 

 pass inwards in the direction of the central canal. (Zeiss apochrom. 

 obj. 2 mm. oc. 12.) 



Fig. 9. Lacerta muralis. Bundles of fibrils (/) running in the direction of the 

 central canal. The small black granules represent cross sections of 

 fibrils running at right angles to the plane of section. (Bausch and 

 Lomb homog. imm. Vi2 oc. 2.) 



Fig. 10. Lacerta muralis (Stage 20 of Peter's Atlas). Fibrils encircling nuclei 

 in the outer cell layer of the spinal cord, and running in the direction 

 of the central canal. 



Fig. 11. Lacerta muralis (more advanced stage than that of fig. 9). Cells in 

 region of ventral roots. a) Basket work arrangement of fibrils about 

 nucleus uniting at c and d to form single filaraent. b) Large nucleus 

 from outer cell layer of cord. (Same magnification as fig. 7.) 



Fig. 12. Pristiurus melanostomus length 5 mm. Giant (Beard) cells in spinal 

 cord. At this stage there seems to be no connection between the 

 individuai fibrils. (Bausch and Lomb homog. imm. 1/12 oc. 2.) 



Fig. 13. Scyllium eanicula length 6 mm. Giant ganglion cells with the com- 

 mon net in process of formation. (Zeiss apochrom. obj. 2 mm. 

 oc. 12.) 



Fig. 14. Scyllium eanicula length 6 mm. Two giant cells with common net. 

 (Zeiss apochrom. obj. 2 mm. oc. 18.) 



Piate 24. 



Fig. 15. Scyllium eanicula length 6 mm. Giant cells with common net. (Zeiss 



apochrom. obj. 2 mm. oc. 18.) 

 Fig. 16. Lacerta muralis — Stage 20 of Peter's Atlas Spinal ganglion cells. 



(Same magnification as Fig. 1.) 

 Fig. 17. Scyllium eanicula length 11 mm. Spinal ganglion cell (c) process of 



giant cell running just beneath epidermis. (Same magnification as 



fig. 1.) 

 Fig. 18. Pristiurus melanostotnus length 9 mm. Fibrils from N. ventralis 



spinalis at inner border of myotome creeping in between the nuclei. 



(Zeiss obj. D. oc. 3.) 



