I judge of this from having held at different
times a poker heated to dull redness near some worms, at a distance
which caused a very sensible degree of warmth in my hand. One of
them took no notice; a second withdrew into its burrow, but not
quickly; the third and fourth much more quickly, and the fifth as
quickly as possible. The light from a candle, concentrated by a
lens and passing through a sheet of glass which would intercept
most of the heat-rays, generally caused a much more rapid retreat
than did the heated poker. Worms are sensitive to a low
temperature, as may be inferred from their not coming out of their
burrows during a frost.
Worms do not possess any sense of hearing. They took not the least
notice of the shrill notes from a metal whistle, which was
repeatedly sounded near them; nor did they of the deepest and
loudest tones of a bassoon. They were indifferent to shouts, if
care was taken that the breath did not strike them. When placed on
a table close to the keys of a piano, which was played as loudly as
possible, they remained perfectly quiet.
Although they are indifferent to undulations in the air audible by
us, they are extremely sensitive to vibrations in any solid object.
When the pots containing two worms which had remained quite
indifferent to the sound of the piano, were placed on this
instrument, and the note C in the bass clef was struck, both
instantly retreated into their burrows.
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