624 
ME. W. K. PAEKEE ON THE STEUCTUEE AND 
cartilage in front of the fenestra ovalis, and that part of the stapes which fits into this 
closed fossa is invested, on its outside, with a tissue that I failed to make out in my 
earlier researches. This tissue is a soft mass of fusiform cells, and is in shape like a half- 
opened fan, the sharp handle of which is twisted a little, and finds its way behind, and 
a little outside the pedicle of the condyle (figs. 6, 7, c.jgd ., co.). This soft tissue fills in 
the inverted fossa beneath the fore part of the tegmen ; it fines away to a point in front, 
but is copious where it lies in front of, and begins to invest, the stapes. 
I do not suppose that the whole of this tract chondrifies ; there is more of it than is 
wanted to form such a “ columella,” as we shall see in the next stage (fig. 8, co.). My 
view is that a filiform “ core ” of cartilage-cells is developed within this mass of tissue, 
and that the last is formed into fibrous connective tissue, the outer part of which is 
loose, and that further inwards more dense, forming the perichondrium of the slender 
rod. 
Skull of Bufo vulgaris. — Sixth Stage. First Summer Toads , 8 lines long. 
The figure here given is carefully drawn from my own preparation ; but I had pre- 
viously supplied Professor Huxley with numbers of young common Frogs of the same 
stage, and my first view of the first stage of a chondrified columella was from his pre- 
parations made from the Frogs. The drawings in his possession (made by him) differ 
in no way from these newer figures made by me ; newer , however, by merely a few 
weeks. 
The quadrate, with its obliquely scooped condyle, turns further backwards than in 
the last stage, the pterygoid ectostosis is spreading further up and down, and the hyoid 
is nearly touched by the leafy tegmen tympani (Plate 55. fig. 8, q.,pg., c.hy ., t.ty.). 
The arcuate “annulus” ( a.t .) is seen, partly, through the chink between the hyoid 
and quadrate. 
The stapes has now acquired its permanent shape (Plate 55. fig. 8, st., and Plate 54. 
figs. 7 & 8, sh). Its otherwise regularly oval form is spoiled by a slightly concave 
emargination outside its fore end ; against this emargination there lies the bulbous end 
of a small styloid cartilage. This rod is gently arcuate, and its convex margin is on the 
inside ; it lies in an extension of the primary inverted fossa (see Second Stage, fig. 4, au.), 
which we saw began very near the mandibular “ elbow,” and then grew backwards. 
This style is the “ columella ” (co.) ; it fills the chink in front of the excavation of the 
stapes, a good distance from the fenestra ovalis, and growing forwards, turns outwards 
also, pricking its way by its delicate filiform end, between the tegmen and the condyle 
of the pedicle (t.ty., c.jgd.). It is evident, if we compare this rod with the perfect 
columella, that the extrastapedial plate and the suprastapedial rod (Plate 54. figs. 7, 8, 
e.st., s.st.) have in this stage no existence ; they are aftergrowths from the filiform end. 
In our native Frog, by the first autumn the columella has become quite perfect 
(“ Frog’s Skull,” plate viii. figs. 7, 8, 8“, p. 172) ; not, however, in the manner of the Toad. 
The points of importance in which the Toad’s skull differs from the Frog’s are the 
following : — 
