OF THE SKULL IN THE UKODELOUS AMPHIBIA. 
561 
Whilst the gills keep their full size and function, this second basal piece keeps its 
larval condition. Its transformation is a correlate of gill-wasting ; when these wither 
the most remarkable transformations are set up. 
Certain investing bones which were appearing in the last stage are now well seen. The 
prootic and pterotic have been developed in the otic capsule, and now the nasals and 
“ osteo-ectoethmoids ” ( e.eth .) have appeared. The nasals (Plate 26. fig. 1, n.) are thin 
shells of bone that form the inner side of the valvular outer nostril ( e.n .) ; they are sub- 
triangular, and are wedged in between the nasal processes of the intermaxillaries and 
the next bone. This bone, the outer ethmoid [e.eth.), is here a mere splint; in Osseous 
Pishes it forms the ossifying plate of the great prefrontal cartilage (“ Salmon’s Skull,” 
plate 5. fig. 7, l.e.). This bone is twice the size of the nasal, is much like the shell of a 
Mussel or a Cy there ; it articulates with the ascending plate of the maxillary [mx.), and, 
like the nasal, overlaps the frontal [f.). The investing ethmoid and the nasal apply them- 
selves, without ingrafting, to the cartilaginous nasal roof ( na .). The large semioval 
frontals (f.) creep beneath these bones and the nasal processes of the premaxillaries, and 
in their turn overlie the parietals ( p .), which reach the ethmoidal plates. The two great 
roof-bones on each side are nearly of a size ; the parietals have a temporal process and 
fossa ; a notch divides them behind, where they nearly cover the superoccipital plate. 
The growing premaxillaries and maxillaries [px., mx.) now form a very round fore 
face ; their outline altogether forms half a neat ellipse. 
The squamosals are still, like preoperculars, stout and nail-like below, where they 
hind on the quadrate ; they are digitate, with many splintery divisions above, where they 
thatch the auditory eave. 
The vomers and parasphenoid (v., pa.s.) are still quite larval ; the former are mere 
arcuate, obliquely placed plates, bearing a rasp of teeth, and the latter is a splintery 
plank, somewhat scooped above, where it floors the great basicranial fontanelle: 
almost oblong, it has some little side-growth into the ethmoidal and basitemporal 
regions. 
I have the more carefully gone into the details of this stage because of its morpho- 
logical interest, as being one good illustration of a perennibranch. When once its very 
low and primordial gills wither, then a new life crops up in every part of the creature, 
transforming it both without and within. It is good and profitable for comparison with 
what is seen in Proteus, Menobranclius, and Siren, but has also many things that are 
the likeness of what is found in the Selachians and the Dipnoi. It has, indeed, more 
likeness to them than to its neighbours, the Batrachia. 
The next stage takes rank with those Urodeles, such as the great Japanese Crypto - 
branchus and the Menopome, in which the branchiae almost disappear. These form an 
intermediate group of great value, which may be called the Cryptobranchiata. 
Ninth Stage. Large Axolotl (8^ inches long), with gills reduced to \ inch in length. 
This instructive stage I got from Mr. Tegetmeie’s vivarium. It was about the size 
MDCCCLXXVII. 4 K 
