As they are completely immobile, corals were classified as plants up until the mid-18th century, when scientists discovered that their cells lacked walls and chloroplast, the sine qua non of the plant kingdom. Hence, they are animals through and through.
無法移動的珊瑚，長久以來被視為植物，直到 18 世紀中葉，科學家才確認它沒有細胞壁，細胞中也缺少葉綠體，是不折不扣的「動物」。