and pugnacity, the orioles gain immunity from attack
by their close resemblance to the protected species. When Dr. Sclater,
the distinguished ornithologist, was examining Mr. Forbes's collections
from Timorlaut, even his experienced eye was so taken in by another of
these deceptive bird-mimicries that he classified two birds of totally
distinct families as two different individuals of the same species.

Even among plants a few instances of true mimicry have been observed. In
the stony African Karoo, where every plant is eagerly sought out for
food by the scanty local fauna, there are tubers which exactly resemble
the pebbles around them; and I have little doubt that our perfectly
harmless English dead-nettle secures itself from the attacks of browsing
animals by its close likeness to the wholly unrelated, but
well-protected, stinging-nettle.

Finally, we must not forget the device of those animals which not merely
assimilate themselves in colour to the ordinary environment in a general
way, but have also the power of adapting themselves at will to whatever
object they may happen to lie against. Cases like that of the ptarmigan,
which in summer harmonises with the brown heather and grey rock, while
in winter it changes to the white of the snow-fields, lead us up
gradually to such ultimate results of the masquerading tendency. There
is a tiny crustacean, the chameleon shrimp, which can alter its hue to
that of any material on which it happens to rest. On a sandy bottom it
appears grey or sand-coloured; when lurking among seaweed it becomes
green, or red, or brown, according to the nature of its momentary
background. Probably the effect is quite unconscious, or at least
involuntary, like blushing with ourselves--and nobody ever blushes on
purpose, though they do say a distinguished poet once complained that an
eminent actor did not follow his stage directions because he omitted to
obey the rubrical remark, 'Here Harold purples with anger.' The change
is produced by certain automatic muscles which force up particular
pigment cells above the others, green coming to the top on a green
surface, red on a ruddy one, and brown or grey where the circumstances
demand them. Many kinds of fish similarly alter their colour to suit
their background by forcing forward or backward certain special
pigment-cells known as chromatophores, whose various combinations
produce at will almost any required tone or shade. Almost all reptiles
and