TREE FROGS 
it to be. Under the skin of the back is a bony plate, 
which is to be looked upon, as far as our present know- 
ledge goes, as a relic of the largely developed skin 
armature of some extinct forms of amphibians belonging 
to the well-known Labyrinthodonts. The green colour 
is quite an amphibian green ; it might be termed perhaps, 
—according to a classification of greens that we have 
seen recently, neither light nor dark, but “ pleasing.” 
Specimens have been on view at the Zoo at any rate 
since the year 1859. 
A GREEN TREE FROG 
It is a common belief that all tree-frogs are green. 
This is not the case ; some are mottled brown and of the 
general Batrachian colour. Buta good many are green ; 
and, as is the case with green tree-snakes and green tree- 
lizards, it is probable that they suck some profit there- 
out. The invisibility, however, is due to colour and 
not to form. Flat and adpressed to the leaf or stem 
though the frog sits, it is said that a photograph at once 
betrays its presence. Nature or a water-colour drawing 
may be deceptive ; notso the camera. With the excep- 
tion of three species, of which one, that concerning 
which we shall have something to say here, is European 
and Asiatic, the tree-frogs are confined to America and 
to Australia. Since they are not always green, it be- 
comes important to be able to say what a tree-frog is 
by some other method than a mere inspection of colour. 
The Hylide, called after the youth beloved of the Naiads, 
but who declined to dwell with them in fountains, 
differ from most other frogs in the adhesive pads de- 
veloped upon their fingers and toes which allow them 
to sit tight upon smooth surfaces, and the existence of 
teeth in the upper jaw. The former character alone 
is not enough. The common tree-frog, Hyla arborea, 
287 
