Starfish
Aiton's Encyclopedia (1910)
a marine animal usually regarded as the type of radiate animals. The common starfish of the Atlantic coast is found from Labrador southward, being especially numerous on oyster beds. An apple-shaped body or disk in the center has a single opening or mouth on its lower surface, and is surrounded by five pointed rays. A corresponding animal on the British coast is called "five-fingered-Jack." Disk and rays are covered with a skeleton of many loosely connected rough pieces of limy shell. The starfish has neither jaws nor teeth. It is thought that a sensitive spot near the end of each ray is an eye, and that a blunt tentacle close by it is an organ of smell. The starfish travels mouth downward by a system of tiny feet or suckers along the under side of each ray. These feet are the ends of tubes connected with a central water reservoir under muscular control. If the animal desires to move eastward, the feet along the eastward arm are filled with water and protruded to their utmost length. They adhere to the surface by suction or atmospheric pressure. By exhausting the water along this arm, they may be shortened. They are not able to let go, and so drag the whole animal eastward. In this way a starfish can ascend a vertical wall or move about on the under side of a board. In feeding, the star-fish arches its body over an oyster, turns its stomach inside out through its mouth, absorbs the juices of the oyster, draws its stomach inside again and is fed. Starfishes are a pest to an oyster bed, and are a source of trouble to fishermen. There are many other curious facts about the starfish, which, of course, is not a fish at all. Sometimes the arms are so short that they are mere angles of a pentagon. In some species each arm becomes four. Ordinary starfish are the size of one's hand. One Pacific starfish is two feet in diameter. See Animal ; Sea-Urchin
What Has Changed in the Last Century
Aiton's 1910 account is sound on the mechanics — the water-vascular system, the everted stomach, the eyespot at each arm tip — though the tube feet do not grip by "suction or atmospheric pressure" as it supposed: they secrete and then chemically release an adhesive, which is why a starfish can in fact let go at will. The bigger shift is in reputation. Where 1910 saw chiefly "a pest to an oyster bed," ecologists after Robert Paine's 1960s experiments on the Pacific Pisaster made the starfish the original "keystone species," the predator whose removal collapses the whole shore community. Since 2013 sea star wasting disease has killed billions of animals along the Pacific coast of North America; the sunflower star, Pycnopodia helianthoides, was listed as critically endangered in 2020, and on the Great Barrier Reef crown-of-thorns outbreaks are managed as a threat to coral. Biologists now usually say "sea star," for the reason the entry itself gives: it is not a fish at all.
Written for this edition, 2026.