The Reactìona of the Vertebrate Embryo to Stimulation etc. 581 



Fig. 19. Lacerta rnuralis — Stage 20 of Peters Atlas Neurofibrils thicker 

 than those within the cord, and curiously twisted have reached the 

 inner surface of the myotome. At B thick bundles split up into 

 finer fibrils that pass inwards in direction of centrai canal, while some 

 may he seen nmning parallel with the periphery to form commissural 

 tracts. (Same magnification as fig. 1.) 



Fig. 20. Torpedo ocellata length 7 mm. N. ventralis spinai with sheath 

 cells clustering about the bundles of fibrils — in marked contrast to 

 Fig. 18. (Same magnification as fig. 1.) 



Piate 25. 



Fig. 21. Pristiurus melanostomus length 9 mm. Bündle of fibrils extending 

 from cord in the direction of myotome unaccompanied by sheath 

 cells. (Zeiss obj. D. oc. 5.) 



Fig. 22. Torpedo ocellata length 14 mm. In this section the great contrast 

 between the calibre of fibril-bundles lying without, and those within 

 the cord is very striking. The intramedullary fibrils split up into 

 extremely delicate filaments which seem to form a very fine network 

 best studied in the immediate vicinity of the ventral horn cells. (Zeiss 

 apochrom obj. 2 mm. oc. 8.) 



Fig. 23. Pristiurus melanostomus length 13 mm. Brauches from N. vent. 

 spin. entering myotome. The ends of fibril-bundles are never bulbous 

 as they are represented to be in sections stained by Ramon y Cajal's 

 method, when silver is frequently deppsited about the distai end of 

 nerve forming an artefact. 



Fig. 24. Torpedo ocellata — length 14 mm. Plexus of fibril bundles formed 

 by the union of ventral and dorsal roots. (Same magnification as fig. 1.) 



Fig. 25. Torpedo ocellata Semi-diagramatic representation of course of fibrils 

 in this Plexus D L. dorso - lateral brauch with filament entering 

 myotome. 



Fig. 26. Lacerta muralis. Sympathetic Plexus. (Same magnification as fig. 1.) 



Fig. 27. Lacerta tnuralis. Cells of Sympathetic Plexus : [a] Loose brush-like 

 arrangement of fibrils uniting to form a single bündle (I) which may 

 be followed in the section to (e) where it splits up again. — IL Fibrils 

 encirciing nucleus. — III. Fibril a may be traced in unbroken con- 

 tinuity into the thicker fibril b. (Zeiss apochromat. obj. 2 mm oc. 8.) 



Fig. 28. Torpedo ocellata length 14 mm. Bündle of fibrils from Vagus with 

 filaments entering epidermis. (Same magnification as fig. 1.) 



