140 



vagi* (r. lat. prof, x.), coursing below the above, and 

 between the dorsal and lateral musculature, far from the 

 surface. The latter gives off no branches until it passes 

 upwards and outwards to supply the sense organs of the 

 posterior half of the main portion of the lateral canal. It 

 is at intervals very closely connected with branches from 

 .spinal nerves, but no fibres are exchanged as far as we 

 could see. The superficialis division, besides supplying 

 its portion of the lateral canal, gives off in front and above, 

 in fact as its first branch, the R. lateralis recurrens vagi 

 (1. rec. w.). This is also a true lateral line nerve distri- 

 buted to pit organs, and must therefore not be confounded 

 with the R. lateralis accessorius (trigemini), although in 

 some fishes its homologue appears to accompany the latter. 

 Its course, which is very extensive and just under the skin, 

 is shown in the chart, and it corresponds precisely to the 

 similar branch arising from the facial, and called the R. 

 lateralis recurrens facialis (/. rec. vii.). 



N e r V u s V a g u s — X. 



Arises by a single large root, which is, however, 

 formed by several large bundles (Stannius says 5) uniting 

 just on the surface of the medulla, and which is further 

 reinforced by two very small bundles in front, as shown 

 in the chart. This root {r. x.) is quite distinct both from 

 the roots of the glossopharyngeus and lateralis,! and in 

 fact the roots of these three nerves are more distinct and 

 clear in the Plaice than in most Teleosts. The vagus root 



* These nerves must not be confused with the R. lateralis trigemini of 

 the Cod (cp. Parker's " Zootomy"), which is not represented in the Plaice 

 at all. The latter is a communis nerve supplying its own, and not 

 lateral, sense organs. It has no connection typically with the trigeminal 

 nerve, and should be called the R. lateralis accessorius. 



t Stannius states that fibres pass from this root to the root of the 

 lateralis in the Plaice, but this is not the case. 



