*Phylum Nematoda consists completely of Roundworms.
*Two types: parasitic and free-living. 90,000 species known; many more exist!
*These Roundworms are unsegmented; they have long, narrow, cylindrical bodies that taper to a fine tip in the posterior and a blunt end at the head. Also, they have a cuticle--a tough layer of outerskin--covering their entire bodies.
*They are pseudocoelomates. They have a pseudocoelom, an internal body space surrounding the endoderm tissue of the digestive tract and surrounded by the mesoderm tissue.
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