DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
257 
next in the Tadpole, after it the prootic, right and left. Later on the fronto-parietals, 
and after them the premax diaries appear ; much later the maxillaries, nasals and 
quadrato-jugals, and later still, as a rule, the squamosals : last of all the generalised 
annular ethmoid or “ girdle-bone ; ” it is mostly contemporary with the shaft of the 
columella. 
But the appearance of the bony tracts, outer or inner, is but a small part of the 
matter; the changes in the fundamental chondrocranium are the most marvellous. 
The organic concussion of the metamorphosis, so to speak, causes the removal of 
some things that are disturbed by it, and the transformation of others, which, in new 
forms, are put to new uses. 
Whilst the large upper labials are still at their highest development two new small 
pairs appear, fitting, the inner to the end of the nasal process of each premaxillary, and 
the outer round each outer nostril, as a valve ; this is at the time that the opercular 
(or “ spiracular ”) cartilage becomes free. 
The band from the junction of the pedicle with the skull in front of the ear to the 
end of the suspensorium with its condyle for the mandible, is, in the larva, a long- 
arcuate tract two-thirds the length of the head : the cross band uniting this with the 
ethmoid, on the contrary, is very short. These relative lengths are, during meta¬ 
morphosis, entirely reversed ; the suspensorium becomes short and the pterygo-palatine 
band two-thirds the length of the skull. The pedicle, and the longitudinal part of the 
suspensorium (without the orbitar process), together, answering to the suborbital band 
of the Lamprey ; the upper and outer regions are absorbed. 
As to position, also, the condyle for the short mandible gets, in many cases, to the 
end of, or even behind, the skull, whereas it did reach nearly to the front; and 
then carries a long mandible which passes to the front. The outer or hyoid bar is 
carried with this pier, and gets under the fore part of the ear-capsules instead of, as 
once, in front of the eye-ball. Thus a small terminal suctorial, is exchanged for a 
widely-gaping inferior, mouth; a mouth like that of a Lamprey is exchanged for one 
like that of a Crocodile. 
The cornua trabeculae become merely the angulated subnasal tract or floor, united in 
front and above by the intertrabecular tract. Each cornu near its inner edge, below, 
develops a small hook-shaped secondary cornu, the “ pro-rhinal,” which is imbedded 
between the laminae of the premaxillary. 
Whilst the pterygo-palatines are becoming, from a short band, a long arch, the 
palatine bones appear in front, transversely, and the pterygoid bones, behind, as a 
forked tract—forked to invest the lower face of the new and short pedicle and the 
inner face of the quadrate region. 
In some forms—species of Rana— the pedicle has its own tract of bone—a distinct, 
“metapterygoid.” Whilst the bones are appearing the sub-apical part of the suspen¬ 
sorium grows into a large leaf of cartilage, ready to become pedate, with a terminal, 
sub-convex, oval condyle. This condyle, so far from its original root, articulates with 
2 L 
MDCOCLXXXI. 
