102 GEORGE W. BARTELMEZ 
chiefly from the vestibular nerve and are largely equilibratory in 
nature. According to Beccari, the root fibers which are related to 
the lateral dendrite in Salmo come from the ramus sacculi of the 
vestibularis. The evidence in Ameiurus is perfectly clear that 
fibers from both vestibular roots enter the bundle which surrounds 
the lateral dendrite. In view of Parker’s (’09) work, on hearing 
in fishes they are not necessarily all equilibratory (p. 114). 
The lateral dendrite retains its larval proportions more nearly 
than any of the others; the whole lateral side of the perikaryon 
tapers off into it. The series from which figure 10 is taken was 
‘cut in the plane of the lateral dendrite and so it appears without 
the foreshortening that comes of reconstructing a transverse 
series (figs. 6 and 11). Figure 10 shows that one, occasionally 
two, branches arise from it- Be but these are slender 
and difficult to recognize. 
The synapse between the lateral dendrite and the VIIIth root 
fibers in Salmo is as Beccari has described it, a simple neuropil 
in the midst of Deiters’ nucleus. But the withdrawal of the 
~ VIIIth root from Mauthner’s cell has brought about a change 
in siluroids which is manifested in all developmental stages. We 
may assume that in the course of phylogeny the VIIIth roots 
were crowded farther and farther back by the gustatory VIIth 
root, yet Mauthner’s cell remained stationary and its lateral 
dendrite did not elongate. So at least we interpret the facts, 
which are as follows. 
In the youngest Ameiurus larvae which I have studied (11 mm. 
long) and in all subsequent stages, the lateral dendrite does not 
arborize at the lateral periphery of the medulla as in Salmo, but 
ends farther medialward dorsal to the spinal V tract, and its 
terminal branches are reduced almost to nothing. This condi- 
tion is shown in figure 3. The nature of the synapse is also al- 
tered from what it is in the more generalized fishes. The den- 
drite is enveloped in a sheaf of thick VIIIth root fibers which 
end in club-like expansions upon its surface (unXed. VIII, figs. 
10, 11 and 18). The reduced terminal branching is shown in 
figure 10 at Br.L.Dend.; there are never more than two or three 
of these slender processes and they come into relation: with col- 
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