In the very middle of the lower part of the body of a starfish is its mouth. This is generally rather large, for the animal feeds chiefly on shell-bearing animals which it swallows whole, shells and all. Then, when it has digested the bodies of its victims, it turns their empty shells out again through its mouth. That is an odd way of feeding, isn't it? But sometimes it feeds in an odder way still, for when it finds a creature which is too big to be swallowed, it will actually turn its own digestive organs out of its mouth, wrap them round its victim, hold them there until it is digested, and then drag them in again and go off to look for another victim!
Starfishes eat a great many oysters in this way. So many do they destroy, indeed, that they are the very worst foes with which oyster-fishers have to deal, and the damage done by them in one single oyster-bed on the coast of North America is estimated at no less than fifty thousand dollars every year.
There are a great many different kinds of starfishes. One, for example, has twelve rays instead of five, and looks very much like a live sunflower. This is called the sun-star. Another has its five rays all joined together by webbing, very much like the toes on a duck's foot, and is known as the bird's-foot star. It is a very handsome creature, for while the greater part of its body is bright yellow, it has a broad band of crimson running all the way round the outer margin, and another stripe of the same color down the outer edges of each ray, while the membrane between them is fringed with yellow hairs. But you are not very likely to find it, for it lives in rather deep water, and is hardly ever caught except by means of that useful net which is called a dredge.
Odder by far than any of these, however, are the brittle-stars, which owe their name to their extraordinary habit of breaking themselves to pieces! They nearly always do this if they are touched or alarmed. In fact, they are so ready to do so that it is very difficult indeed to obtain a perfect brittle-star for a museum. The creature just gives a kind of shudder, and its five rays all drop off and break up into little pieces, all that is left of the animal being just the central disk. But it does not appear to suffer any pain, and loses hardly any blood. And before very long new rays grow in the place of the old ones, so that in a few weeks' time the starfish is just as perfect as ever!
The brittle-stars have five very long and very slender rays, which are generally fringed on either side with yellow hairs. And these rays are hardly ever still, but twist and writhe and curl about so actively that they really look almost like so many centipedes! It is by no means so numerous as the fivefinger, and is so easily broken that it is hard to find a whole one on the beach.
Very curious, too, is the basket-star, which at first sight does not look like a starfish at all. The reason is that, close to its body, each of the five rays divides into two. Then each of the branches divides into two again, and each of those into two more, and so on over and over again, till sometimes there are more than eighty thousand little arms altogether!
The basket-star catches its prey by means of these wonderful rays, which it wraps all round it in the form of a circular basket. It is not at all a common creature, and is only found in deep water.
But perhaps the oddest of all these creatures is the rosy feather-star, which actually grows on a stalk while it is young, and looks just like a flower with its petals spread. The stalk, which is fastened down to a rock at the bottom of the sea, is made up of a great number of tiny joints, and grows longer and longer. And when it reaches its full length the animal breaks itself free and swims away, leaving the stem behind.
The rosy feather-star lives in rather deep water, from which it is sometimes brought up by means of the dredge. It can crawl about on the ground by means of its sucker-like feet, and can swim through the water with some little speed. And very often, to save itself trouble, it will cling by means of its rays to a piece of floating wood, and allow itself to be carried for long distances by the waves.
In Great Britain these may often be found near shore, but the American feather-stars all live in very deep water. They are all that remain of a large class of such animals which abounded in the very ancient seas, whose fossil remains are called stone-lilies.