Among the echinoderms the methods of feeding are interesting. The sea-cucumber holds fast to a rock by means of the suckers at the tips of its tube-feet, and, with tentacles widely expanded like the branches of a tree, waits for minute crustaceans and the larvae of all sorts of animals to comfortably settle themselves upon the hospitable branches. Then, with the least possible motion, the sea-cucumber very gradually bends a tentacle over and into the mouth, and, as it is again extended one of the two small tentacles scrapes off the resting organisms. So each tentacle, in rhythmical succession, takes its turn in the feeding process. Some species of star-fishes have large mouths and can swallow snails and mussels whole, sometimes consuming as many as twenty-five or thirty mollusks of various kinds at one meal. Other star-fishes have mouths too small to receive the animals commensurate with their appetites and so they simply turn their stomachs inside out, covering over a clump of oysters, and thus forming a sort of external stomach into which the secretion from the digestive glands is poured. When the soft parts are thus dissolved and absorbed the star-fish pulls in its stomach and goes on in its devastating course. The sea-urchin has an apparatus known as Aristotle's lantern providing five strong teeth worked by powerful muscles with which it catches live worms and crabs. The sea-crawfishes, built like lobsters except for the absence of the large pincers, most perfectly convey the impression of life on the bottom of the sea. They seem like uncanny agents of evil as they solemnly stalk about over the rocks, poking their great antennae into each other's affairs and always having several claws out for a fight, yet seldom engaging with one another. Some of the veterans, however, have lost an antenna, or a leg, and the missing parts are being regenerated.
