EARTH SCIENCE > BIOLOGICAL CLASSIFICATION > ANIMALS/INVERTEBRATES > ROUNDWORMS
Roundworms are mostly worm-like and unsegmented, with an external cuticle,
a pseudocoelom between body wall and gut, an anus and complex nervous
system but not circulatory system. They are mostly free living bottom
dwellers in marine and freshwater environments and in the soil.
Burn, David M. Animal World. 1980. Octopus Books Ltd. London.