wn hares in arctic regions after him. Or,
suppose, on the other hand, it were a brown fox who invaded the domain
of eternal snow. All the hares and ptarmigans of his new district would
behold him coming from afar and keep well out of his way, while he, poor
creature, would never be able to spot them at all among the white
snow-fields. He would starve for want of prey, at the very time when the
white fox, his neighbour, was stealing unperceived with stealthy tread
upon the hares and ptarmigans. In this way, from generation to
generation of arctic animals, the blacker or browner have been
constantly weeded out, and the greyer and whiter have been constantly
encouraged, till now all arctic animals alike are as spotlessly snowy as
the snow around them.

In the desert much the same causes operate, in a slightly different way,
in favour of a general greyness or brownness as against pronounced
shades of black, white, red, green, or yellow. Desert animals, like
intense South Kensington, go in only for neutral tints. In proportion as
each individual approaches in hue to the sand about it will it succeed
in life in avoiding its enemies or in creeping upon its prey, according
to circumstances. In proportion as it presents a strikingly vivid or
distinct appearance among the surrounding sand will it make itself a
sure mark for its watchful foes, if it happen to be an unprotected
skulker, or will it be seen beforehand and avoided by its prey, if it
happen to be a predatory hunting or insect-eating beast. Hence on the
sandy desert all species alike are uniformly sand-coloured. Spotty
lizards bask on spotty sands, keeping a sharp look-out for spotty
butterflies and spotty beetles, only to be themselves spotted and
devoured in turn by equally spotty birds, or snakes, or tortoises. All
nature seems to have gone into half-mourning together, or, converted by
a passing Puritan missionary, to have clad itself incontinently in grey
and fawn-colour.

Even the larger beasts that haunt the desert take their tone not a
little from their sandy surroundings. You have only to compare the
desert-haunting lion with the other great cats to see at once the reason
for his peculiar uniform. The tigers and other tropical jungle-cats have
their coats arranged in vertical stripes of black and yellow, which,
though you would hardly believe it unless you saw them in their native
nullahs (good word 'nullah,' gives a convincing Indian tone to a
narrative of ad