224 JOHN BEARD. 



Fig. 48. Low-power drawing of transverse section through nose of an 

 adult Triton showing Blaue's smell-buds (sm.b.). 



Fig. 49. High-power drawing of two such smell-buds. Z. f, oc. 2, 

 cam. luc. 



Fig. 50. Diagrammatic transverse section through the gill-bearing 

 region of an Elasmobranch or other Ichthyopsid. Nervous 

 system not yet closed in. On the left side the gill muscle 

 plate is shown, and on the right the gill-cleft, h.c. Head 

 cavity, n.s. Nervous system, p.r. Posterior root. n. Noto- 

 chord. p.br.o. Branchial sense organ, br.gl. Branchial 

 ganglion, l.m. Lateral muscle plate, p.n. Post-branchial 

 nerve, al.c. Alimentary canal. 



Fig. 51. Diagram taken partly from my own drawings and partly 

 from Prof. Marshall's. Shows the ganglia and various 

 branches of the cranial nerves. Also mouth (m.) and gill- 

 clefts (cl.i, cL 2 ), &c. For lettering, see general list. 



