Sacoelomate (they have no body cavity), triploblastic (the body has three tissue layers), and bilaterally symmetric (they have symmetric right and left sides and usually a definite head), and they have organ systems, including an excretory, digestive.

Feature of non-patasitic worm:

Bilaterally symmetrical.

Body having 3 layers of tissue with organs and organelles

Body contains no internal cavity.

Has Protonephridial excretory organs instead of an anus.
Has normally a nervous system of longitudinal fibres rather than a net.
Generally dorsoventrally flattened.
Reproduction mostly sexual as hermaphrodites.

Features of parasitic worm:

Mostly they feed on animals and other smaller life forms.
Some species occur in all major habitats, including many as parasites of other animals.

Possesses a blind gut (i.e. it has a mouth but no anus)



These worms have a complete digestive system and are more complex than the flatworms (phylumPlatyhelminthes) but lack a circulatory system and other advanced features found in the annelids (segmented worms).

Feature of parasitic:

Nematodes have a complete gut with a mouth and an anus. Teeth, which are used to pierce animal or plant matter, aid in obtaining food.

having both male and female reproductive organs. In dioecious species, males have a specialized spine forsexual reproduction that is used to open the female's reproductive tract and to inject sperm


  • Symmetry and Size. Annelids are all bilaterally symmetrical animals. ...
  • Coelom. Nearly all annelids have a fluid-filled cavity between the outer body wall and the gut, and this is referred to as a coelom
  • Body wall
  • Parapodia
  • Nervous system
  • Sense organs
  • Circulation and respiratory structures
  • Segmental organs

Feature of non-parasitic:

It uses it pharynx to suck food or soil into its mouth

The oesophageal glands add chalk to neutralizes any acidity in the soil

The gizzard has a lining which helps grind up the food into smaller particles

Feature of parasitic:

a cylindrical or slightly flattened body with suckers at either end for attaching to prey. The leech, like other annelids,

the mouth has three small jaws equipped with sharp teeth

hermaphroditic and cross-fertilizing.

salivary secretions of the leech contain hirudin, an anticoagulant, and other substances that promote blood flow