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.
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