Agnes did not suffer this permission to lie dormant; and she gathered sea-weed of a great variety of shades of pink, brown, green, black, and even white; as, however, she could not carry half the quantity she had collected, her mother promised to bring her back to the beach the following morning, if the weather should be fine, when she might provide herself with a basket.
They now found the tide coming in so rapidly that they judged it most prudent to return; though Agnes, who was fond of excitement, would willingly have gone on a little farther, in spite of the danger; which, indeed, was not very great, as the tide seldom rises very high on the back of the Isle of Wight, and there was a considerable space between the cliffs and the shore. The billows, however, came in with considerable force, and they brought with them a piece of board that looked as if it had belonged to a ship. Agnes picked it up, and found some Mussels sticking to it; one of which was attached by what looked like a tuft of coarse brown thread; but, when she asked what it was, her mother smiled, and told her it was the Byssus.
“The Byssus!” cried Agnes: “I thought that was produced by the Pinna, or Sea-wing. Don’t you remember, mamma, showing me a pair of gloves made of the Byssus of the Pinna at the British Museum? I am sure you said the Pinna.”
Fig. 22.
Freshwater Mussels (Dreissena polymorpha).
“I remember it perfectly; but other shell-fish produce Byssus besides the Pinna.”
“Indeed! and are gloves made of it?”
“I believe not; because it is not produced in other shell-fish in sufficient quantities.”
“Do not some Mussels produce pearls?” asked Agnes.
“Those are the River Mussels,” said Mrs. Merton. “Remember that there are several kinds of Mussels: as, for example, the River Mussel, or Unio, which produces what are called British pearls, and which is common in many British rivers, particularly in the Conway, in Wales, and in the Tay, in Scotland; the Sea Mussel, or Mytilus, the animal of which is eaten, and which produces the Byssus; and the Horse Mussel, or Modiola. The kind you have found, however, belongs to none of these, as it is a freshwater species generally found in docks; and it must have adhered to some vessel that has been shipwrecked here soon after it left the dock in which it had been repaired.”