78 
MR. TV. K. PARKER ON THE STRUCTURE AND 
This new cartilage ( co .) lies inside the nerve, as it forks to join the glosso-pharyngeal 
(VII., IX.), and to supply the region of the first cleft, fore and aft. 
This rudimentary columella appears as a solid bud of cartilage abutting against the 
fore edge of the large, almost circular, stapes (st.). 
A section of these parts (Plate 11, fig. 9, st., co .) shows-that, according to the rule in 
the Batrachia, the dorsal end of this cartilage is wedged in between the antero-superior 
margin of the stapes and the auditory capsule ; it is already constricted into two 
regions; the massive “ inter-stapedial ” part (a distinct segment generally, but not in 
Pseudis (see Plate 10, fig. 4, m.st.), is already marked off from the main rod (Plate 11, 
fig. 9, co.). Below the stapes (Plate 11, fig. 8 ,fty.) the tympanic floor, once so large 
as a down-growth of the actual skull-base, is now a mere thickening of the bulbous 
vestibular region. 
The prsemaxillaries (Plate 12, fig. 1, px.) have been added to the bony plates, and 
they fit against a small inner (anterior) cartilage ( u.l .); a crescentic valve to the nostril 
is also found outside this ; the large primary upper labials have been removed ; they 
were ready to be absorbed. 
If the metamorphosis of this skull stayed here, we should have much to contemplate 
that is both striking and instructive ; this stage, however, is scarcely mid-way to the 
actual end of this changing skull. 
17 (continued).—(D) Fourth larva of Pseudis, rapidly acquiring the Frog-form, but 
with a tail still 3 inches long and 7 lines wide. 
In this species the tail co-exists for a long while after many of the characters of the 
adult skull have appeared (Plate 12, figs. 2-7). At first sight this larva appeared to 
be not very different from the last, but it had lost the contracted suctorial mouth, and 
had gained the characteristic open gape of an adult Frog. 
This had been done by the rapid enlargement of some parts, and the rapid lessening 
of others—an interstitial change which appears the more marvellous the more it is 
contemplated. 
In the broad basioccipital region the notochord (Plate 12, figs. 2, 3, nc.) still persists 
as a small thread; and a three-rayed tract of cartilage has escaped the ex-occipital 
growths ( e.o .); the lateral extensions of cartilage are the occipital condyles ( oc.c .), 
which are large and wide apart. 
The cranial cavity has become still wider than in the last; it lessens gently up to 
the ethmoidal region. 
The parietals are now fairly distinct from the frontals (p.,f), and the hinder part of 
the “ tegmen ” has no uncovered cartilage, the confluent ex-occipitals having the 
narrow part of the subquadrate parietals lying on their fore margin. 
These hinder bones send out a temporal angle behind the widest part of the frontals, 
and then the latter bones continue this down-turned edge (orbital plate) up to them 
narrow apex (fig. 4, /). 
