The New International Encyclopædia/Amphipoda

​AMPHIP′ODA (Gk. nom. neut. pl., from ἀμφί, amphi, around + πούς, pous, foot). An order of crustaceans, distinguished by the sessile, lateral eyes, and the greatly compressed body. They are mostly of small size, and some very minute. Their name alludes to the peculiar arrangement of the so-called walking-feet, four pairs of which point forward and three backward. The abdomen or "tail" is also a powerful locomotive organ, and assists the animal in jumping, which is its usual mode of progression. Even in swimming its movements are chiefly a succession of jumps. The amphipods are usually plainly colored, but some forms are very handsome. A large number of species is known, but zoölogists are by no means agreed as to their classification, some making only two, and some as many as nine, families. They occur in both fresh and salt water, and are especially abundant along sandy beaches, where they skip about in such a lively manner that they are called beach-fleas or sand-hoppers. They are widely distributed over the world, occurring even in the Arctic regions, and are of great practical importance as food for fishes. See Beach-flea, and Crustacea.