SporosacSpo"ro*sac\, n. [Spore + sac.] (Zo["o]l.) (a) A hydrozoan reproductive zooid or gonophore which does not become medusoid in form or structure. See Illust. under Athecata. (b) An early or simple larval stage of trematode worms and some other invertebrates, which is capable or reproducing other germs by asexual generation; a nurse; a redia.