amphibians possess the power of changing their hue in accordance
with their environment in a very high degree; and among certain
tree-toads and frogs it is difficult to say what is the normal
colouring, as they vary indefinitely from buff and dove-colour to
chocolate-brown, rose, and even lilac.

But of all the particoloured reptiles the chameleon is by far the best
known, and on the whole the most remarkable for his inconstancy of
coloration. Like a lacertine Vicar of Bray, he varies incontinently from
buff to blue, and from blue back to orange again, under stress of
circumstances. The mechanism of this curious change is extremely
complex. Tiny corpuscles of different pigments are sometimes hidden in
the depths of the chameleon's skin, and sometimes spread out on its
surface in an interlacing network of brown or purple. In addition to
this prime colouring matter, however, the animal also possesses a normal
yellow pigment, and a bluish layer in the skin which acts like the
iridium glass so largely employed by Dr. Salviati, being seen as
straw-coloured with a transmitted light, but assuming a faint lilac tint
against an opaque absorbent surface. While sleeping the chameleon
becomes almost white in the shade, but if light falls upon him he slowly
darkens by an automatic process. The movements of the corpuscles are
governed by opposite nerves and muscles, which either cause them to bury
themselves under the true skin, or to form an opaque ground behind the
blue layer, or to spread out in a ramifying mass on the outer surface,
and so produce as desired almost any necessary shade of grey, green,
black, or yellow. It is an interesting fact that many chrysalids undergo
precisely similar changes of colour in adaptation to the background
against which they suspend themselves, being grey on a grey surface,
green on a green one, and even half black and half red when hung up
against pieces of particoloured paper.

Nothing could more beautifully prove the noble superiority of the human
intellect than the fact that while our grouse are russet-brown to suit
the bracken and heather, and our caterpillars green to suit the lettuce
and the cabbage leaves, our British soldier should be wisely coated in
brilliant scarlet to form an effective mark for the rifles of an enemy.
Red is the easiest of all colours at which to aim from a great distance;
and its selection by authority for the uniform of unfortunate Tommy
Atkins reminds me of nothin