ASCIDIA, a genus of animals belonging to the or-
der of vermes mollusca. The body is cylindrical, and fixed to a shell, rock, &c. It has two apertures: one on the summit, the other lower, forming a sheath. There are six species of this animal, viz. the papillosum, gelatinosum, intestinalis, quadridentata, rustica, and echinata; only one of which, viz. the rustica, is found in the British seas. Animals of this genus have the faculty of squirting out the water they take in.