254 Journal of Comparative Neurology. 



which go out from the n. ambiguus to the striated bran- 

 chial musculature. If these latter fibres have been 

 derived from the pre-ganglionic system, they have cer- 

 tainly suffered a most remarkable metamorphosis. If, as 

 implied in Cole's remark above, they have not been thus 

 derived, we should find it difficult to find any homologue 

 for them in the trunk and we may be led to assume that 

 they belong primarily to the branchial region, for several 

 lines of current research seem to hint at the possibility 

 that this region may be older than the trunk after all. 



5. — The Root of the R. Lateralis Vagi. 



The root of the lateral line nerve, after separating from 

 the lateral aspect of the tuberculum acusticum (610) 

 and emerging from the oblongata immediately dorsally of 

 the origin of the IX nerve, as it passes caudad, sinks down 

 until it comes to rest upon the dorsal surface of the ramu- 

 lus ampullae posterioris (Fig. 17). At this level it begins 

 to be crowded laterally by the emerging vagus root, upon 

 the ectal surface of which it is closely appressed without, 

 however, anastomosing with it at all. It passes through 

 the same foramen as the vagus. The auditory ramulus 

 referred to almost immediately separates and turns laterad 

 to the proper auditory organ, without any interchange 

 of fibres with the lateralis root. 



The lateral line nerve at its origin is not composed ex- 

 clusively of the characteristic very large and heavily 

 myelinated fibres, but there are numerous medium-sized 

 fibres. These may be diffusely scattered through the 

 trunk or they may be gathered into rather compact bundles, 

 whose positions and relations, however, vary in different 

 specimens. They can be followed into the ganglion of 

 the lateral line nerve. Their peripheral relations and 



