No. I.] THE CRANIAL NERVES OF AMPHIBIA. 20 1 



the ascending Trigeminus, but the lobus vagi and lobus tri- 

 gemini taken together, represent continuations of the spinal 

 cord; that in the tadpole the lobus vagi (fasciculus communis) 

 can be traced, enormously diminished, into the cord a short 

 distance at least ; and that, according to Ahlborn (i), and also 

 according to Ransom and Thompson (50), the Vagus, as well 

 as the Trigeminus, in Cyclostomes, come from centers rep- 

 resenting continuations of parts, though different parts, of the 

 cord. Mayser (41) and Ahlborn are in accord, however, in 

 considering the Acusticus-lateralis center as something distinct 

 and superadded. Even in Cyclostomes, however, the Vagus 

 center is a considerably enlarged and developed center in the 

 medulla. 



Returning to Kupffer, it would next seem probable that his 

 lateral element, which is derived from the dorsal fusion with 

 the epiblast, is represented by the lateral-line element, plus, 

 perhaps, that to the end buds; and that, finally, his epibranchial 

 ganglia are represented by the ganglia of nerves terminating 

 centrally in the lobus vagi (= fasciculus communis + terminal 

 nucleus = fasciculus solitarius + sensory nucleus IX + X). 

 Whether the ganglia of the nerves supplying the end buds can 

 be considered as belonging to or representing this series rather 

 than the preceding is a question whose answer depends upon 

 the answer to the correlated question, already considered, as to 

 the relation between the lobus trigemini and lobus vagi. 



IV. General Considerations. 

 I . Relation of Cranial and Spinal Nerves. 



Hatschek (30) has made some interesting and suggestive 

 comparisons between the nerves of Amphioxus and Ammo- 

 coetes, which at the same time throw more light upon the 

 origin of such nerves as the lateralis and visceralis, and of the 

 differences obtaining between the cranial and spinal nerves. 

 In brief, this view is as follows : In Amphioxus the dorsal root 

 divides into a dorsal and ventral branch. The dorsal branch 

 subdivides into a N. cutaneus dorsalis and a N. lateralis dor- 

 salis. The ventral branch divides into a N. cutaneus ventralis, 



