OF THE SKULL IN THE UKODELOUS AMPHIBIA. 
543 
The nerve-cells that are becoming the ganglia of the 5th and 7th nerves in front, and 
the ganglia of the 9th and 10th nerves behind (5, 7, 9, 10, figs. 1 & 2, and 5, fig. 8) are 
large and conspicuous masses. 
The auditory sacs are now chondrified to a great extent below and outside. Prof. 
Huxley’s figure, op. cit. plate xxxi. fig. 1, au., shows them as membranous at this stage ; 
but the stained preparations correct this error. A large oval tract above is membranous, 
and a lesser tract in front of this is granular ; the rest is thin cartilage. The base 
(fig. 2, au.) is well chondrified, and the fenestral cleft has not yet appeared. The sec- 
tions (Plate 21. figs. 8-10) show the structure and condition of these capsules. In fig. 8 
the anterior and horizontal canals are shown well in section ( a.s.c ., h.s.c). Below and 
in front of the capsule the ganglionic mass of the 5th and 7th nerves is shown (Plate 23. 
fig. 8), and behind the capsule the ganglion of the 9th and 10th (9, 10, Plate 21. 
fig. 10). 
The large mandibular arch is now well developed, and its pier shows three out of 
four of its spurs or processes. The pterygoid outgrowth is much later. 
As no amount of controversy has sufficed to make Professor Huxley’s observations on 
the mandibular pier quite agree with mine, I shall show what I have seen, stage by 
stage, gladly naming the regions with his well-chosen terms. 
The cartilage of the “ pier ” closely embraces the front of the ear-capsule ; the 
flattened hinder part, which thins out and is afterwards clamped by the squamosal, is 
the “ otic process ” ( st.p .). 
The true apex of the mandible is roughly bifurcate, and the upper knob, which has 
no counterpart in the Frog, is the “ ascending process ” ( a.p .). 
The lower knob, which corresponds to the band which in the Frog coalesces with 
the elbow of the trabecula (“ Frog’s Skull,” plate 5. figs. 1-4, m.pg. ; see it also 
free in the embryo Salmon, “ Salmon’s Skull,” plate 2. figs. 3 & 7, mt.pg), is 
the pedicle ( pd .). It lies below the orbito-nasal nerve and the ascending process 
above it. 
Neither of these processes is yet modified by coalescence with the trabecula. The 
pedicle never does coalesce (as in the adult Frog, where it is the only inner process) ; 
but the “ ascending process ” does unite, by cartilage, to the alisphenoidal wall. 
Even now the ascending process has come closer to the trabecula than the pedicle ; 
the attachment of the pedicle is now (and always in the Urodeles) to the inner face 
of the ear-capsule in front. This relationship is secondary in the Frog, whose 
pedicle wastes above, and then expands further down into a large facet (“ Frog’s Skull,” 
plate 8, m.pg., and plate 9. figs. 2 & 7, m.pg), whose attachment is to a like 
cartilaginous surface on the ear-capsule ; this surface is a “ plaster ” derived from the 
basal plate. 
The free mandibular bar (mJc) continues to elongate, and it is losing the deflection 
at the chin. A dentary plate ( d ) is now added to the outside of the rod, besides the 
dentigerous “ splenial.” 
