Nematomorpha

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Nematomorpha (hairworms; phylum Aschelminthes) A small class or phylum of pseudocoelomate, unsegmented worms, the vast majority of which are marine. Their narrow, hair-like bodies have a thick cuticle. All lack a true excretory system. The young are parasitic, and mature individuals are free-living in fresh water. They are first recorded from the Eocene.