Ascaris : Ascaris lumbricoides is also known as the common roundworm. The roundworms are different from the flatworms and tapeworms as they have cylindrical body, pseudocoelom and a complete digestive tract lined by endodermal epithelium.
Most of these roundworms are free living but some parasitic worms also exist. The species belonging to the genus Ascaris are largesized and they inhabit in the intestines of the vertebrate hosts. Ascaris lumbricoides is the most common roundworm which is the gastro-intestine parasite of the man.

Ascaris body cavity : A spacious fluid filled cavity is present between the body wall and the visceral organs. The fluid filled cavity is called as pseudo coelom and it cannot be considered as the true coelom as,

• It is not lined by the coelomic epithelium.
• It also has no relation with the reproductive and excretory organs.
• It is developed from the blastocoel.