148 THE SALAMANDER 



and developed posterior to the rudiment of the hyomandibular 

 cleft, while the plica hyomandibularis was a secondary structure, 

 developing behind the R. alveolaris VII, and in no way related to 

 the visceral cleft. The true R. pre-trematicus VII he identified 

 with a small branch of the R, palatinus VII distributed to the quad- 

 rate. In his later paper, 1 904, he confirmed these results. 



Thus the matter stands, and the accepted views with regard to the 

 questions enunciated above may be summarized. 



(i) The chorda tympani is a post-trematic branch of the Vllth nerve. 



(ii) The R. alveolaris VII of Urodeles is the true homologue of the 

 chorda tympani of Mammals. 



It should be noted that the above resume is confined to the more 

 immediately relevant literature and that all reference to the more 

 general, but nevertheless important papers by Cole, Goodrich, 

 Herrick, and Ruge, has been omitted for the sake of brevity. 



Very close to the point from which the R. alveolaris separates, the 

 R. communicans IX-\-X ad VII (r.9 + 10— 7) joins the main nerve. "^ 

 Driiner claims that it brings motor-fibres from the IXth nerve which 

 join those of the R. jugularis VII. This is almost certainly incorrect. 

 Without direct observation it is unsafe to make a definite statement, 

 but it seems very probable that the condition in the Salamander 

 resembles that described by Coghill for Amblystoma, viz. that the 

 Xth nerve stndiS general cutaneous fibres which enter the R. jugularis 

 VII, while the IXth nerve contributes communis fibres to the R. 

 alveolaris VII. One feature which strongly supports this assumption 

 is that one not infrequently finds the R. communicans bifurcating 

 just before reaching the Vllth nerve, and one portion, the smaller, 

 passing towards the R. alveolaris, and the other entering the R. 

 jugularis about a millimetre further distalwards. It should, however, 

 be noted that the same author can find no glossopharyngeal fibres 

 in the R. communicans of Triton but only general cutaneous fibres 

 from the vagus. 



After the separation of the R. alveolaris from the Truncus hyo- 

 mandibularis the remainder of the nerve becomes known as : 



R. jugularis (n.j.) (visceral motor, and general cutaneous derived 

 from vagus). 



R. mandibularis externus ...... Hoffmann. 



Its first branch, {a\ arises very close indeed to the point where the 

 R. communicans IX +X ad VII enters it, and in fact it usually 



^ The R. communicans may be easily displayed by dissecting the M. depressor 

 mandibulae away from its origin on the squamosal and turning it over ventrally. 



