"An animal," said Norah. "Where can such an animal live?""It lives," said Fred, "at the bottom of the sea, and a strange life it must be. It cannot move about, for it is fixed to the rocks by a sort of root.""I suppose," said Norah, "as this is only the skeleton that we see, it must have some flesh on it when it is alive?""Oh yes," said Fred, "but the flesh is only a sortof soft jelly. That all runs away, when it is taken outof the water. Nothing is left but the tough, elastic, porous framework of its body.""But," said Norah, "if it is an animal, I suppose it has a mouth; it must eat.""Well," said her brother, "it has a great many mouths. All these little pores in the sponge are so many mouths. Teacher says it feeds by drawing itself up, and then swelling out again. You know that the sponge is very elastic.
