152 THE SALAMANDER 



interesting example of the transition from a primitive fish-like state 

 towards the condition found in more specialized land vertebrates. 

 For example, the fourth and fifth visceral arch nerves retain a 

 considerable amount of independence, and remain definitely asso- 

 ciated with their respective arteries, while the nerve belonging to 

 the sixth visceral arch has become more specialized, although still 

 easily recognizable, and travels for a considerable distance in the 

 track of the intestinal trunk. A careful study of PI. X, fig. 54 will 

 make this clearer. 



(i) Fourth ^visceral arch nerve (n.vis.4). 



2nd Gill-arch nerve ....... Druner. 



Nearly always this nerve leaves the ganglion together with the 

 fifth visceral arch nerve, but occasionally they remain quite distinct 

 from the start. It passes lateral to the M. opercularis, and mesial to 

 the M. cucullaris, as do the other visceral nerves emerging from the 

 glossopharyngeus-vagus ganglion. Its course round the oesophagus 

 lies between the carotid and systemic arches. About 4 mm. distal to 

 the ganglion it gives oflF: 



{a) R. pharyngeus (n.phar.) which passes back mesially over the 

 roof of the pharynx to enter the pharyngeal complex mentioned 

 above. 



(b) RR. cutanei jugulares (n.cut.j.) which are given off at about the 

 level of the carotid gland. They correspond with those already 

 described for the glossopharyngeal nerve. 



A short distance beyond this point the nerve divides into two ter- 

 minal branches (<:) and {d). 



(c) R. muscularis for the M. subarcualis rectus I (s.r. i) passes 

 ventral to the common carotid, then, turning lateralwards, enters the 

 muscle at the posterior end. It usually unites with a corresponding 

 branch from the R. recurrens intestinalis X, and sometimes with one 

 from the fifth visceral arch nerve also. According to Druner this 

 muscular branch may be missing, but no such case has been met 

 with by the present author. The nerve between the arterial arches 

 and the muscle is greatly convoluted, thus allowing for the free 

 movement of the hyobranchial apparatus. 



(d) R. recurrens (n.rec.4). This is a sensory branch and passes 

 dorsal to the common carotid. It ramifies over the middle region 

 of the mouth-floor, to the mucous epithelium of which its fibres 

 are distributed. Druner reports occasional ganglion cells along 

 its course. 



The same author considers that the whole visceral nerve as de- 



