CoGHiLL, Cranial Nen>es of Ambly stoma. 275 



into the r. alveolaris after the former nerve has been joined by 

 the r. communicans. 



According to Hoffmann ('78) this r. communicans is 

 absent in Proteus and Menobranchus, and according to Platt, 

 also, it is wanting in Necturus. Druner, on the contrary, 

 finds the nerve in a reduced condition in both these forms. It 

 is probable, therefore, that the nerve occurs in all Urodela. 



Drlner's idea concerning the function of the r. commu- 

 nicans deserves special attention here. He says (p. 496) : 

 "So scheint es, als ob die vom R. jugularis versorgte Muscu- 

 latur in alien Theilen von Glossopharyngeus-Elementen 

 durchsetzt ist. " This relation, he believes, is brought about 

 through the r. communicans. 



Now it is very plain in serial sections that many of the 

 terminal ramuli of the r. jugularis contain both motor and gen- 

 eral cutaneous fibers. Moreover, Druner's method of dissection 

 does not seem to me adequate to determine the exact nature of 

 these terminal ramuli as they appear in serial sections. Further- 

 more, he has obviously been deceived concerning the function 

 of a part of the r. supratemporalis which is very like these 

 ramuli in its relation to the muscles and skin. 



A most important objection to Drijner's interpretation is 

 that it does not account for the presence of the general cu- 

 taneous fibers which are known to be in the r. jugularis. Such 

 fibers cannot come from the t. hyomandibularis in Amblystoma, 

 nor in any other amphibian which has been studied from the 

 point of view of nerve components. Moreover, general cu- 

 taneous neurones from the third vagus root enter the r. com- 

 municans in Amblystoma. Neurones, also, enter it from the 

 glossopharyngeus which appear to be communis. Therefore, 

 if there is a motor component in this nerve in addition to these 

 two known components, that component must be extremely 

 small and can scarcely have such an important function as 

 Druner assigns to it. 



Druner's statement (p. 540) that fibers sometimes pass 

 from the r. communicans directly to the m. cephalo-dorso- 

 mandibularis (depressor mandibulae) is also open to some ques- 



