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Its larvae is excreted, and sets up house in a water snail.

It was just what it seemed to be, the shell of a water snail.

It is nothing but the cast off shell of a water snail.

It begins its life in a water snail, transfers itself through the mouth and skin to the body of any human being it can, and there makes hay of his or her internal arrangements in a peculiarly distressing manner.

Of two kinds of water snail found in the Thames, and among the commonest molluscs, one is a vegetable feeder.