That some physical change is produced in the nerve-cells
or nerves which are habitually used can hardly be doubted,
for otherwise it is impossible to understand how the tendency
to certain acquired movements is inherited. That they are
inherited we see with horses in certain transmitted paces,
such as cantering and ambling, which are not natural to them,--
in the pointing of young pointers and the setting of young setters--
in the peculiar manner of flight of certain breeds of the pigeon,
&c. We have analogous cases with mankind in the inheritance
of tricks or unusual gestures, to which we shall presently recur.
To those who admit the gradual evolution of species,
a most striking instance of the perfection with which the most
difficult consensual movements can be transmitted, is afforded
by the humming-bird Sphinx-moth (_Macroglossa_); for this moth,
shortly after its emergence from the cocoon, as shown by the bloom
on its unruffled scales, may be seen poised stationary in the air,
with its long hair-like proboscis uncurled and inserted
into the minute orifices of flowers; and no one, I believe,
has ever seen this moth learning to perform its difficult task,
which requires such unerring aim.
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