“I can understand that, mamma; and so I suppose that these poor oysters enjoy the warmth of the sun and the flowing of the tide, as much as I do the fresh breeze when it blows against me as I run.” “Exactly so. Every creature has a capability of happiness adapted to the situation in which it is placed; and when we do not perceive how this is effected, we may rest assured that the fault is in ourselves, and not in the system of Nature.” While they were conversing in this manner, they had strolled to a considerable distance along the beach, and were beginning to think of turning back, as they were going from the Chine, which they intended to visit before they returned to the inn, when Agnes’s attention was attracted by a splendid mass of tangle, that had been thrown on the beach by the sea; and catching hold of it, she picked up at the same time a little crab not bigger than the end of her finger. The little crab was of a pale yellow, and as soon as it was caught, it began to run sideways as fast as possible. Agnes had often heard of crabs running sideways, but she had never seen one do so before; and the motions of this little creature struck her as so very odd that she burst into a violent fit of laughter. Mrs. Merton came up to know what was the matter; and when she saw the little crab running sideways as fast as possible with only half of its legs, and then back with the other half, she could not forbear smiling also. The next moment, however, she checked herself. “We ought not to laugh at this little creature,” said she, “since there is nothing really ridiculous that is natural; but it only strikes us as absurd because we are not used to it.” “What curious creatures crabs are!” cried Agnes. “They are called Crustaceous animals,” returned her mother, “because they are covered with a crust or shell; and they are said to be articulated, because their limbs are jointed so that they can throw one off without suffering much inconvenience.” “Lobsters can do the same thing, can they not?” “Yes, they also belong to the Crustacea, and so do shrimps, and prawns, and cray-fish, besides many other creatures you are not acquainted with. All the Crustacea have also the power of throwing off their shells when they have grown too large for them, and forming new ones, as I think I explained to you some years ago when we were speaking of cray-fish.” [Illustration: _Fig. 20._ IRISH MOSS, OR CARRAGEEN. (_Fucus crispus._) ] “They must suffer a great deal of pain when they change their shells.” “They do; and some are said even to die under the operation; but I suppose they must also suffer a good deal from the old shell being too tight for them, before they throw it off.” Agnes now picked up some sea-weed which struck her as being like what her mother had once taken, boiled with milk, for a troublesome cough. “It is the same,” said Mrs. Merton; “the popular name is Carrageen, or Irish moss, but it is a kind of Fucus.”