108 PEOP. MARSHALL AND MR. SPENCER. 



to that of the fifth. These relations are well seen in the transverse 

 section drawn in fig. 6. This shows, as already noticed, the primary 

 and secondary roots of the seventh, and also the proximal portion of 

 the nerve vii d. This nerve is seen to be a direct continuation of the 

 primary root ; its inner, or deeper, portion is seen on both sides to 

 become continuous with the maxillary branch of the fifth (v 6), the 

 junction of the two forming the connection between the fifth and 

 seventh nerves already noticed. Beyond this point of union the nerve 

 vii d is continued downwards, lying immediately superficial to the 

 maxillary nerve (v b). The two nerves preserve this relation up to 

 their terminal distribution, two of the ultimate branches being 

 represented in figure 5 (v b and vii d). This very remarkable branch 

 of the seventh puzzled us greatly for a long time, and it was only 

 after working out the whole history of its development up to stage Q 

 that we succeeded in determining its import. The nerve has already 

 been described and figured by one of us, 1 and named tentatively the 

 palatine. This determination now proves to be erroneous ; the palatine 

 is a deeply placed nerve, whereas the nerve vii d retains its superficial 

 position in the adult. 



This nerve (vii d) we have now identified as the buccal nerve, the 

 proof of this determination, consisting in our having traced the nerve 

 directly up to the adult. The buccal nerve has always hitherto been 

 regarded as a branch of the fifth, and is described as such by Stannius, 2 

 Gegenbaur, 3 Jackson and Clarke, 4 Balfour, 5 and others. Stannius 6 

 points out that the buccal nerve in fishes is very variable ; that it may 

 either arise from the main stem of the fifth, from the maxillary or the 

 mandibular, or from both these nerves, or, finally, may be absent 

 altogether. 



Up to stage n, as shown in figures 6, 11, and 12, the buccal nerve 

 is clearly a branch of the seventh, and could not possibly be taken for 

 a branch of the fifth. After stage n, however, the connection between 

 the roots of the fifth and seventh nerves becomes, as we have seen, 

 very much more intimate ; and at the stage between o and p, 

 represented in fig. 14, the buccal nerve (vii d), which is now situated 

 completely in front of the maxillary (v b), might very easily be taken 



i Marshall, loc. cit., pp. 86, 87 ; and Pis. V, fig. 15, and VI, figs. 28 and 29. 

 12 * Handbuch der Zootomie,' p. 158. 



3 Loc. cit., p. 609. 



4 Loc cit., p 86. 

 6 Op. cit., p. 195. 



' Das Peripherische Nervensystem,' pp. 41 and 42. 



