Physa

‖prop. n. [ NL., fr. Gr. fysalli`s a bladder, fr. fy^sa a bellows. ] (Zool.) A genus of large oceanic Siphonophora which includes the Portuguese man-of-war. [ 1913 Webster ]

☞ It has a large air sac, or float, with a sail-like crest on its upper side. Numerous zooids of different kinds are attached to the under side of the float. Some of the zooids have very long tentacles; some have a mouth and digest food; others produce gonophores. The American species (Physalia arethusa) is brilliantly colored, the float being pink or purple, and bright blue; the zooids blue. It is noted for its virulent stinging powers, as well as for its beautiful colors, graceful motions, and its ability to sail to windward. [ 1913 Webster ]

‖n. pl. [ NL. ] (Zool.) An order of Siphonophora which includes Physalia. [ 1913 Webster ]