The main characteristics of Nematohelminthes are given below:
1.These are aquatic, terrestrial and parasitic.
2. Body is slender, sylindrical unsegment.
3. A false psydoceloum is present.
4. Except excretory system and respiratory system all organ system are well developed.
5. Nervous system with circumcentric nerve ring.
6. Excretory organ consists of flame cells.
7. Sexes are separate.
8. Fertilization is internal and develops in direct.