aprimulgus rupestris) which rests in the bright sunshine on
little bare rocky islets in the Upper Rio Negro, where its unusually
light colours so closely resemble those of the rock and sand, that it
can scarcely be detected till trodden upon.

The Duke of Argyll, in his "Reign of Law," has pointed out the admirable
adaptation of the colours of the woodcock to its protection. The various
browns and yellows and pale ash-colour that occur in fallen leaves are
all reproduced in its plumage, so that when according to its habit it
rests upon the ground under trees, it is almost impossible to detect it.
In snipes the colours are modified so as to be equally in harmony with
the prevalent forms and colours of marshy vegetation. Mr. J. M. Lester,
in a paper read before the Rugby School Natural History Society,
observes:--"The wood-dove, when perched amongst the branches of its
favourite _fir_, is scarcely discernible; whereas, were it among some
lighter foliage, the blue and purple tints in its plumage would far
sooner betray it. The robin redbreast too, although it might be thought
that the red on its breast made it much easier to be seen, is in reality
not at all endangered by it, since it generally contrives to get among
some russet or yellow fading leaves, where the red matches very well
with the autumn tints, and the brown of the rest of the body with the
bare branches."

Reptiles offer us many similar examples. The most arboreal lizards, the
iguanas, are as green as the leaves they feed upon, and the slender
whip-snakes are rendered almost invisible as they glide among the
foliage by a similar colouration. How difficult it is sometimes to catch
sight of the little green tree-frogs sitting on the leaves of a small
plant enclosed in a glass case in the Zoological Gardens; yet how much
better concealed must they be among the fresh green damp foliage of a
marshy forest. There is a North-American frog found on lichen-covered
rocks and walls, which is so coloured as exactly to resemble them, and
as long as it remains quiet would certainly escape detection. Some of
the geckos which cling motionless on the trunks of trees in the tropics,
are of such curiously marbled colours as to match exactly with the bark
they rest upon.

In every part of the tropics there are tree-snakes that twist among
boughs and shrubs, or lie coiled up on the dense masses of foliage.
These are of many distinct groups, and comprise both venomous and
harml