182 J. B. JOHNSTON, 
collaterals first to a grey mass anterior (ventral) to the nucleus of 
Burpacx and later to a grey mass lying close to the posterior com- 
missure. This bundle continues as far as the end of the pyramidal 
decussation. 
It is evident that the fasciculus solitarius with the upper and 
vertical nuclei in Mammals are directly homologous with the lobus 
vagi in fishes and with the fasciculus communis and its accom- 
panying cells in Amphibia, or so much of these structures as are 
related with the IX and X nerves in the lower Vertebrates. The 
nucleus of the commissure (CAJAL) is undoubtedly homologous 
with the nucleus which I have described in Acipenser, Amia, and 
tana. The cervical bundle is probably better developed than in the 
lower Vertebrates. Neither commissure nor cervical bundle have 
been described before in the lower Vertebrates. 
Since writing the above the final paper of C. J. HERRICK (99) 
on Menidia has appeared. The close agreement of our independent 
results on Acipenser, Amia, Coregonus, Catostomus, Menidia, Mugil, 
and Rana gives strong support to the conclusion that the con- 
ditions described by Cagaz for Mammals will be found common to 
all Vertebrates. This must go far toward clearing up the question 
of visceral centers in the cord, of which I speak in the succeeding 
paragraphs. ' 
Conclusions on the lobus vagi. — The questions of 
present interest regarding the lobus vagi are those raised in my 
preliminary paper on the hind brain of Acipenser, namely: a) its 
relation to the dorsal horn of the cord and to the other sensory 
nuclei in the medulla; b) its homologue or representative in the 
cord; and c) does it serve as the end nucleus of a specific variety 
of fibres in the peripheral nerves? The first of these questions can 
be answered definitely. There is no evidence of any continuity of 
tissue, similarity of minute structure, or correspondence in the course 
and destination of the secondary tracts on which to base the conclusion 
that the lobus vagi or its homologue is a continuation or representative 
of the dorsal horn or any part of it, or that the lobus vagi or its homo- 
logue is directly related to or to be compared with the acusticum. 
In all Vertebrates this system forms a separate and distinct sensory 
center which serves as the end nucleus of the VII (nerve of Wris- 
BERG), IX, and X nerves. In fishes the secondary tract from this 
nucleus is an uncrossed tract running to a definite nucleus in 
the cephalic end of the medulla. In Vertebrates above the fishes 
