No. 1.] AMPHIBIAN BRAIN STUDIES. 67 
inal system, with no apparent homology in the 
arrangement of its nuclei to either.} 
There is a strong ground for supposing that the fasciculus 
communis, although primarily given off with the Auditory, 
subsequently joins the Facial, since, first, it adjoins the lower 
motor bundle of the Facial, and second, it also joins the motor 
bundles of the roth, 9th, and probably of the 5th, nerves, which 
fall into the same general category as the 7th. Still, this ques- 
tion can only be settled by following this tract peripherad beyond 
the passage of the 8th into the auditory capsule. 
The posterior longitudinal fasciculus is stated by 
some authors to send a bundle to the 7th; I do not know 
that this has been positively determined. Spitzka regards it as 
highly improbable that this bundle enters the Auditory proper. 
It forms aclose union with this nerve, VII.-VIII., 3-4, soon after 
its exit, at which point the two facial and four auditory roots 
have the relations, shown in Fig. 16, to each other and to the 
large Auditory ganglion. It seems improbable, from these rela- 
tions, that this inferior bundle should unite with the facial bun- 
dle, and further, both Ahlborn? (83, p. 262) and Fulliquet 
(86, p. 81) have followed portions of these large fibres into the 
Auditory so that this tract is almost without doubt a portion 
of this nerve. There is also much similarity between the 
disposition of the 7th, 8th, and 5th tracts in Cryptobranchus and 
Petromyzon (op. cit., Taf XIV.). 
Facialis and Trigeminus. As already stated, the nuclei and 
tracts of the upper and lower /aczal bundles arise at a low level, 
opposite the exit of the 9th pair, somewhat lower, in fact, than 
represented in the scheme, Fig. 21. There is no difficulty in 
recognizing the upper tract as sensory, since it springs from 
the outer fold of the medulla in precisely the same manner as 
1 Dr. E. C. Spitzka, to whom I am indebted for some valuable suggestions as to 
the identification of these tracts, questions the determination of the upper bundles, 
7 u-l, in Fig. 15, as parts of the Facial, on the ground that the ventral position of 
the Auditory reverses the usual order. There can, however, be no doubt that these 
belong to the Trigeminal system, from the fact that 7 « passes directly to the Gasse- 
rian ganglion (see Fig. 5). 
2 Ahlborn distinguishes three groups of Miillerian fibres in Petromyzon, viz., 
lateral uncrossed, median crossed, and median uncrossed. The 
same groups are apparently present in Cryftobranchus. The first named corresponds 
in position with the posterior longitudinal fasciculus, and alone enters 
the Auditory root. See Appendix, Note 3. 
