^■. KuPFFER, Cranial Nerves of ]'ertebratcs. 349 



agreement between cranial and spinal nerves, he himself dis- 

 covered at the same time facts w^hich cause the distinction 

 between both groups to appear more marked than was 

 hitherto supposed. On one side, he shows that the dorsal 

 cranial nerves in respect to their course bear relations 

 to the somites entirely different from the spinal nerves, 

 and it furthermore emerges from his investigations 

 that the epidermis participates in the development of 

 the peripheral twigs of the cranial nerves, as G6tte(') 

 and Semper(-') had already affirmed for the N. lateralis 

 vagi. 



Concerning the relation to the mesoderm, the dorsal 

 cranial nerves first take their course over the mesoderm 

 and on between the somites and the epidermis, but the 

 dorsal roots of spinal nerves pass within and below 

 the somites. This distinction is so important that it was 

 especially by this that C. Gegenbaur was driven to abandon 

 the homodynamy of cranial and spinal nerves, which he had 

 previously defended. 



According to Van Wihje's discovery, the facial, glosso- 

 pharyngeus and vagus enter into close connection with the 

 epidermis in a double row of points. On the one hand, 

 fusion of their ventral branches occurs at the upper hinder 

 side of the gill cleft which lies cephalad; on the other hand, 

 the rudiments (Anlage) of their dorsal branches fuse with 

 thickened portions of the epidermis. From the dorsal places 

 of connection are developed portions of the lateral -line sys- 

 tem with its nerves, in such a way that Van Wihje thought 

 the participation of elements of the epidermis in the forma- 

 tion of the nerves might be regarded as certain. P'rom the 

 places of fusion of the ventral branches with the epithelium 

 of the gill clefts the terminal twigs of those branches are 

 developed. 



1 " Embryology of the Toad." 



2 "Urogenital System of Plagiostomes," Arbeiten aus d. Zool.-Zoot. Institute zu 

 Wurzburg, Rd. II, p. 398. 



