PHYLUM NEMATODA. Round worms, generally much elongated, with a single layer of longitudinal muscles in the 

 body wall. Nervous system as a ring in the anterior part of the body giving off nerves backwards and forwards 

 Body cavity but no vascular system. Male generative organs open into cloaca. Amceboid spermatozoa. Often parasitic 

 Ex. Ascaris, Filaria, Trichina, Rhabditis. 



