222 JOHN BEAED. 



Auditory nerve, vg. Vagus nerve, vg.gl. Vagus ganglion. 

 Z. a, oc. 2, cam. luc. 



Fig. 28. High-power drawing of auditory portion of preceding. Shows 

 auditory nerve not yet separated from skin. Z. f, oc. 2, 

 cam. luc. 



Fig. 29. Transverse section through auditory region of an Elasmo- 

 branch embryo. Shows auditory ganglion and auditory 

 thickening intimately fused together. Auditory involu- 

 tion as yet only partial. 



Fig. 30. Similar section under low power. Auditory involution com- 

 plete. 



Fig. 31. Highly-magnified drawing of auditory portion of last sec- 

 tion. Shows intimate fusion of ganglion and thickening, 

 and proliferation of cells of thickening into ganglion. 

 Many nuclear figures near proliferating portion. 



Fig. 32. Transverse section through hind-brain of a Torpedo embryo. 

 Shows glossopharyngeal nerve (ix) just fused with its 

 primitive branchial sense organ (jp.br.o.). Z. c, oc. 2, 

 cam. luc. 



Fig. 33. Similar section to preceding. Vagus nerve (x) just before 

 fusion. Z. c, oc. 2, cam. 



Fig. 34. Similar section. Vagus nerve just fused with its thickening. 

 Post-branchial branch (p.n.) passing on to muscles of cleft. 

 Z. d, oc. 2, cam. 



Figs. 35 & 36. Portions of similar sections to preceding. Portions of 

 vagus ganglion (vg.gl.) above gill-cleft, and just separating 

 from skin; in separating, leaving a nerve behind, p.hr.o. 

 Branchial sensory thickening, phr. Pharynx, cl. Cleft. 

 T. ocellata. Z. d., oc. 2, cam. luc. 



Plate IX. 



Fig. 37. Horizontal section through head of a Torpedo embryo. Shows 

 hyoid prse-branchial nerve (jo.hr.7i.) forming in epiblast. 



Fig. 38. High-power view of small piece of preceding section, showing 

 hyoid pr@e-branchial nerve (p.br.n.) in epiblast. Z. f, oc. 2, 

 cam. 



Fig. 39. Horizontal section through Torpedo embryo. Vagus ganglion 

 separating from the skin. Lateral line (l.l.) growing back- 

 wards and pushing indifferent epiblast (i.e.) away, sp.gl. 

 Spinal ganglion. Z. a, oc. 2, cam. luc. 



