It is strange to see a quiet-looking shell suddenly take
to hopping and jumping like an acrobat.
To perform this astonishing feat the Cockle makes use of its foot, which
is worked by very strong muscles. It is large and pointed, and bent: if
the Cockle wishes to move quickly, it stretches out its foot from
between the shells, as far as it will go. Then, by using all its power,
it leaps backwards or forwards in a surprising manner.
There are many other interesting molluscs, besides those we have looked
at. The Piddock, or Pholas, is a smallish, rather delicate one, with a
soft foot. But this foot is a most wonderful boring tool, fitted with a
hard file. Hard rocks and wood are perforated by these little molluscs.
Indeed, they are a positive danger, for they pierce the wooden piles of
piers, and weaken them. They cannot pierce through iron, however, and so
iron plates or nails are used to protect the piles from their
onslaughts. You will often see stones and rocks riddled by the Piddock
as if they were as soft as cheese. Chalk, sandstone, or oak, it is all
the same to the Piddock, which rasps them away with its file.
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