Appendicularia

Appendicularia, a genus of Ascidians (q.v.), and type of a small but important order, the members of which retain the larval vertebrate characters which are lost in the more or less degenerate adult sea-squirts. Appendicularia is a minute free-swimming form with a long tail, and closely resembles an Ascidian larva. The brain and dorsal nerve-cord, the long notochord, the two respiratory slits opening directly from the pharynx to the exterior, and other vertebrate structures lost in the adult Ascidians, are here retained throughout life, and demonstrate the true position of the class to which Appendicularia belongs.