nKYET,Or:\FKXT OF TTTR STCFLL TX THE TlATRAf'TTTA. 257 



next in the Tadpole, after it the prootic, riglit and loft. Later on the fronto-parietals, 

 and after them the premaxillaries appear ; much hxter the mnxillaries, 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 liouy 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 ; tliis is at the time that the opercular 

 (or " spiracular ") cartilage becomes free. 



The band fi-om 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. Tiius 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 trabeculse 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 secondaiy cornu, the " jtm-rhinal," which is imbedded 

 lietween 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 liana — the pedicle has its owti tract of bone — a distinct, 

 "meta pterygoid." 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 



MDCOCLXXXr. 2 L 



