When the tide is out, the Limpet clings to the rock, its soft body
tucked safely away in the shell. Its feeding time comes when the water
covers the rocks once more. Then the Limpet's shell may be seen to tilt
up, and a foot, and a head with feelers and eyes, come out. The Limpet
crawls to the seaweed and begins to browse, using a rasp like that of
the Periwinkle. It then crawls back to its own place on the rock. In
time this resting-place becomes hollowed out, and the Limpet's shell
fits into the groove thus made.
Limpets are useful as bait for fish. The Whelk and Periwinkle are
gathered in immense numbers, and are used by us for food. Perhaps you
have seen the egg-bundle of the Whelk. It contains many eggs when first
laid in the sea. Each egg is as big as a pin's head. They swell in the
water, until the yellowish bundle is three times as large as the Whelk
that laid it. You often see the empty bundle blown by the wind along the
shore.
EXERCISES
1. Give the names of two bi-valve molluscs.
2. What is the Periwinkle's shell made of?
3. Describe how the Periwinkle eats seaweed.
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