Finally, the attitude of the
body, the manner of walking, the mode of flight, and the voice, all
exhibit modifications of the most remarkable kind.[35]
_Acclimatisation_.
A very important kind of variation is that constitutional change termed
acclimatisation, which enables any organism to become gradually adapted
to a different climate from the parent stock. As closely allied species
often inhabit different countries possessing very different climates, we
should expect to find cases illustrating this change among our
domesticated animals and cultivated plants. A few examples will
therefore be adduced showing that such constitutional variation does
occur.
Among animals the cases are not numerous, because no systematic attempt
has been made to select varieties for this special quality. It has,
however, been observed that, though no European dogs thrive well in
India, the Newfoundland dog, originating from a severe climate, can
hardly be kept alive. A better case, perhaps, is furnished by merino
sheep, which, when imported directly from England, do not thrive, while
those which have been bred in the intermediate climate of the Cape of
Good Hope do much better.
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