Phylum - Nematoda (Roundworms) Commonly known as round worms,
they are one of the most abundant types of animal on earth. Many
Nematodes are free-living species, while others are parasitic on
animals and plants. They are typically tapered at both ends with
bilaterally symmetry. Round worms have a complete digestive
tract containing a mouth with lips, a gut and anus. The body of
most nematodes are made of a non-cellular cuticle. They have a
nervous system that is simple. Nematodes live in most parts of
the world.