proscolex

from The Collaborative International Dictionary of English v.0.48

Proscolex \Pro*sco"lex\, n.; pl. {Proscolices}. [NL., fr. Gr. ?
   before + ?, ?, a worm.] (Zool.)
   An early larval form of a trematode worm; a redia. See
   {Redia}.
   [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Redia \Re"di*a\ (r?"d?*?), n.; pl. L. {Rediae} (-[=e]), E.
   {Redias} (-?z). [NL.; of uncertain origin.] (Zool.)
   A kind of larva, or nurse, which is prroduced within the
   sporocyst of certain trematodes by asexual generation. It in
   turn produces, in the same way, either another generation of
   rediae, or else cercariae within its own body. Called also
   {proscolex}, and {nurse}. See Illustration in Appendix.
   [1913 Webster]