1 78 STRONG. [Vol. X. 



Regarding the N. lateralis, we find that it has in Selachii a 

 similar character from Shore's account also of the Vagus in the 

 shark. According to him, the lateral-line portion of the Vagus 

 is coarse-fibred and distinct in origin from the rest of the 

 nerve. It also possesses its own ganglion of rather scattered 

 ganglion cells. Its internal organ is not traced. A peculiar 

 feature, however, is that the lateral-line part of the Vagus arises 

 from a number of fasciculi forming the most posterior ii.e., 

 caudal) of the roots of the Vagus, and somewhat more vejitral 

 than the others. This account differs from the exit of this 

 root in Amphibia, Ganoids, and Teleosts, judging from the 

 writer's observations and the papers of Goronowitsch, Mayser, 

 Wright, and Ewart, as shown above. In all of these the 

 R. lateralis has its exit cephalad and dorsad of the rest of the 

 vago-glossopharyngeal roots. 



I may add that in some dissections made at the Marine 

 Biological Laboratory at Woods Holl during the summers of 

 1892 and 1894, upon Galeus canis and Galeocerdo vtaciilattiSy I 

 found also that the R. lateralis invariably arose by a single 

 root cephalad and dorsad of the other roots of the IX + X. I 

 cannot reconcile Shore's account in this respect with those of 

 other investigators or with my own observations. 



The lateral-line nerve, I found, may be reenforced by fibres 

 from one or both of the next two Vagus roots. What the 

 character of these fibres is can only be surmised, and will be 

 discussed below. Ewart and Mitchell (19) have made a similar 

 observation, and judging from what has been quoted (p. 156), 

 some of these at least would be general cutaneous fibres. 



(c) Resume of the Roots in Fishes. — In general, ^he arrange- 

 ment of these roots and principal branches seems to be as follows : 



I. The Trigeminus proper, with fibres of varying sizes, 

 which sometimes arises by two roots, in which case the one 

 cephalad is the R. ophthalmicus profundus. Besides this latter 

 it divides into the R. ophthalmicus superficialis, the R. maxil- 

 laris, and the R. mandibularis. It is this Trigeminus proper, 

 the central continuation of which is an ascending tract from the 

 cord, which has also a ventral motor root added, and is constant 

 in the main throughout the vertebrate series. 



