No. 1.] AMPHIBIAN BRAIN STUDIES. 85 
vestigated the medulla oblongata, especially the origin of the 
cranial nerves and the fate of the Miillerian fibres. The ar- 
rangement of the latter, I have reason to believe, is very similar 
to that in the Amphibia, but this system has not been as yet 
well investigated. His conclusions as to the origin of the 
cranial nerves are in many details supported and confirmed by 
my own, although I have discovered many additional struc- 
tures which either do not exist or have been overlooked in the 
lamprey. 
An important difference is seen as to the more primitive con- 
dition of the medulla in Petromyzon, in that the nerve nuclei 
are more central (Fig. 18), and not confined to the lateral regions 
of the medulla as in the Urodela. In the latter I have ob- 
served the large ganglion cells, gc, opposite the exit of the 
8th, but cannot confirm the entrance of their processes into the 
Auditory roots as observed by Rohon and partly confirmed by 
Ahlborn. He places the 7th and 8th in one group, which I find 
cannot be done in the Uvodela, the 7th being closely related to 
the 5th. 
One chief point of agreement is that in Petromyzon the 7th 
nuclei and exit are dorsal to the 8th; this confirms my 
observations and undermines the hypothesis that the 8th is the 
sensory portion of a typical pair of nerves of which the 7th 
forms the motor element. Our observations agree further in 
respect to the connection of the posterior longitudinal 
fasciculus with the 8th (acusticus haubenbahn, p. 268) ; 
also as to the presence of a nucleus of pale ganglion cells near 
the exit of the 8th (p. 261), which I have found is one of the 
chief Auditory nuclei in the Uvodela; further, the nuclei and 
tracts of the 8th have the same relation to those of the 5th, as 
I have described in Cryptobranchus; finally, in both genera 
the 8th sends a tract into the cerebellum.” 
The resemblance of the main Trigeminal system is also close. 
I do not find the nucleus of the transverse motor tract as 
large as he describes it, but the motor nucleus adjoining the 
ascending tract is similar in form and position (Figs. 16- 
21). -I do not find an upper and lower nucleus of the 8th, 
1 See Appendix, Note 3. 
2 This determination of the Auditory nuclei as ventral to those of the Facial is 
confirmed by both Stieda’s and K6ppen’s observations upon Rana. 
