THE CEREBRAL NERVES 



365 



geal nerves are beKeved to be derivatives of the gangKon crest, their cells migrat- 

 ing ventrally in early stages. 



The central processes from the neuroblasts of the vagus ganglia enter the 

 wall of the myelencephalon, turn caudalward, and, with the sensory fibers of the 



Vagus root ganglion (Jugular) Accessory root ganglia 



IX. root gang. {Superior) 



Br. to carotid plexus 



Gang. Froriep, 



Sympathetic 

 Fig. 365. — A reconstruction of the peripheral nerves in an embryo of 17.5 mm. (Streeter). X 16.7. 



facial and glossopharyngeal nerves, complete the formation of the soHtary tract. 

 The peripheral processes of the ganghon cells form the greatei: part of the vagus 

 trunks after the separation from it of the spinal accessory fibers. 



The Segmentation of the Vertebrate Head. — The vertebrate head undoubtedly 

 consists of fused segments. This was suggested to the earlier workers by the arrangement of 



