Any cellular projection surrounding a cylindrical shaft containing a bundle of eleven microtubules, nine of which form a circle around the central pair, while the cortical microtubules are doublets. Cilia and flagellae (q.v.) are examples. Mastigote protoctists possess undulipodia; amastigote protoctists do not. See axoneme, Rhizopoda.
Subjects: Biological Sciences.