Gregarinae

‖prop. n. pl. [ NL., fr. Gregarina the typical genus, fr. L. gregarius. See Gregarious. ] (Zool.) An order of Protozoa, allied to the Rhizopoda, and parasitic in other animals, as in the earthworm, lobster, etc. When adult, they have a small, wormlike body inclosing a nucleus, but without external organs; in one of the young stages, they are amœbiform; -- called also Gregarinida, and Gregarinaria. [ 1913 Webster ]