There is an opening at the bottom of the stomach through which the food passes after being digested. Sea-water also enters the body through the stomach, and both the water and the nourishment circulate freely through the chambers. Each tentacle is a hollow tube connected at its base with one of the chambers, and readily filled with water. Here we have an explanation of the mysterious manner in which the sea-anemone swells itself out and then shrinks away again. The body and tentacles are enlarged by drawing in water to fill them, and when they are suddenly contracted the water is forced out through the mouth.
The sea-anemone has no hard skeleton whatever; all parts of the body are soft, like a stiff jelly. It can draw its tentacles in out of sight, and it will do so upon the slightest alarm, rolling itself into an ugly lump like the one we found. Allow it to remain quiet for a while, however, and it will blossom out as gorgeously as ever.
When any little crab, or worm, or small fish brushes past the tentacles, the lasso-cells are darted out to paralyze it, and the tentacles seize the prey and pass it to the mouth. The bones or shells which remain after the meal are thrown out from the mouth. The tentacles hold the prey tightly, so that even cunning crabs can not escape, and you know it is not the easiest thing in the world to catch a crab and hold it.
Sea-anemones are greedy creatures. It takes a great deal of food to satisfy their appetites, and their mouths can be extended to receive quite large animals. They eat mussels and cockles by sucking the body out of its shell. Great numbers of sea-anemones, in their turn, are devoured by other animals, their soft bodies offering little resistance.
Fig. 2.—Cluster of Anemones.
The variety of color in these animals is almost endless. Some of them are rich olive and chocolate colors, or purple dotted with green. One beautiful species has violet tentacles pointed with white; another, red tentacles speckled with gray. This one spreads out its green arms edged with a circle of dead white, while that one opens a milk-white top circled with a border of pink. In Fig. 2 is a cluster, of beautiful anemones. The two small ones at the right show how these creatures look when closed.
Some sea-anemones which live in exposed situations are of a dull, dusky brown, covered with rough warts, while animals of the same species, living in deep water, where there is less need of concealment, have smooth skins adorned with brilliant tints of rose, scarlet, or light green. This is a beautiful provision of Nature for protecting the little creatures by rendering them inconspicuous when left upon rocks by the retreating waves.
The number of eggs produced by sea-anemones seems almost incredible. A single animal is said to throw out three hundred eggs in one day. The eggs are little jelly-like lumps which are formed on the inside of the partitions, and are thrown out from the mouth. After swimming about by means of hair-like appendages called cilia, they settle on some solid body and begin to grow. Sometimes the young ones remain within the body of the parent until their tentacles have grown. They are then ready to settle down soon after reaching the water.
Sea-anemones increase by budding as well as by eggs. At the lower edge of the body little round knobs are sometimes formed, which separate from the parent and grow into perfect animals. If the tentacles or other parts of the body are removed, new tentacles soon grow in their places. If an individual is torn in pieces, each fragment has the power of forming for itself a mouth and throwing out tentacles, and becoming a new sea-anemone, perfect in all its parts.