HOLOTHURIA, in zoology, a genus belonging to the order of vermes mollusca. There are nine species, all inhabitants of the ocean. The physalis, called by the Dutch befantyes, by Dampier cutters, and by the English sailors man-of-war, has a half-round body, stands directly upwards, has many long and many short tentacula, is slimy, transparent, somewhat bluish, shines in dark nights, is poisonous, and so light that it will scarce sink in Spanish brandy. Beyond the Cape they are small; in the ocean they are larger and very numerous, especially in March.