200 STRONG. [Vol. X. 



Acusticus center, thus differing from the origin so universal for 

 the N. lateralis in all other forms — it must be regarded as 

 very probable that this nerve does not represent the N. late- 

 ralis vagi of higher forms. Stannius has also called attention 

 to some of these difficulties and reached a similar conclusion 

 (57, p. 96). What it does represent is probably the R. lateralis 

 trigemini, so-called, of Teleosts — a nerve which is formed 

 principally, as we have seen, by a recurrent branch of the Fa- 

 cialis, derived from the lobus trigemini, and which is reenforced 

 by a branch from the Vagus. It would then much more prob- 

 ably innervate the papillae which are so numerous on the dorsal 

 fin, and which probably correspond to the structures innervated 

 by the so-called R. lateralis trigemini. The R. branchialis I 

 would, apparently, represent the R. lateralis. I am forced to 

 believe that the exact anatomy of these nerves is not yet accu- 

 rately known, nor have their connections with the cutaneous 

 sense-organs been sufficiently worked out. With respect to the 

 remainder of the Facialis, it has been asserted by Julin (33) 

 and Dohrn (15) to contain motor elements. If this be true, it 

 probably does not arise merely by the one root, as described. 



If the character of the so-called N. lateralis be as above sup- 

 posed, the most dorsal nucleus of the Acustico-facialis center, 

 from which the Facialis emerges, would correspond to the lobus 

 trigemini. Its structure, as described by Ahlborn, would seem 

 to support this view. If this be the case, it is evident that the 

 distinction between the lobus trigemini, on the one hand, and 

 the ascending Trigeminus and lobus vagi, on the other, is 

 already here sharply drawn, and is quite a primitive feature. 

 This would be in opposition to Mayser's views quoted above 

 (p. 189). The course of the Facialis in the head is not decisive 

 on this point, inasmuch as we have seen that in higher forms 

 the lobus trigemini and lateral-line components go together. 



In comparison with Kupffer's observations (36), it would 

 seem probable that, in general, Kupffer's medial elements 

 derived from the neural crest and common to both spinal and 

 cranial nerves, would be represented by such ganglionated 

 nerves as emerge from the ascending Trigeminus. It must 

 be remembered, however, that, according to Mayser, not only 



