cyst
From ZooTerms (Dictionary of Invertebrate Zoology)
cyst (noun; Greek kystis, bladder): 1. A small sac, capsule or bladderlike structure.
2. A protective covering formed about an organism during unfavorable conditions or reproduction.
3. (NEMATA: Secernentea) The tanned cuticle of certain mature female nematodes (Heterodera or Globodera) in which eggs are retained.
