scolex

from The Collaborative International Dictionary of English v.0.48

Scolex \Sco"lex\, n.; pl. {Scoleces}. [NL., from Gr. skw`lhx
   worm, grub.] (Zool.)
   (a) The embryo produced directly from the egg in a
       metagenetic series, especially the larva of a tapeworm or
       other parasitic worm. See Illust. of {Echinococcus}.
   (b) One of the Scolecida.
       [1913 Webster]