Jellyfish are bell shaped and roundworms aren't. Jellyfish sting and roundworms do not. jellyfish are radial and and roundworms are not.
cylinderical
they are round
Roundworms have long, cylindrical bodies that taper at both ends. They have a complete digestive system with a mouth and an anus, and their bodies are covered in a protective cuticle. Roundworms also have a fluid-filled body cavity called a pseudocoelom.
roundworms have 2 body opening. The mouth and the anus
Roundworms have a cylindrical body shape with a distinct head and tail. They have a digestive system that runs through the length of their body and a nervous system with a simple brain. Their bodies are covered by a cuticle that helps protect them.
roundworms
Bilateral symmetry.
roundworms
The largest organism that can enter the body and cause infection is typically a parasitic worm, such as tapeworms or roundworms. These worms can enter the body through contaminated food or water, and cause infections in various organs.
Roundworms have a simple circulatory system with a dorsal blood vessel that runs the length of the body and pumps nutrients and oxygen to the tissues. The blood is not contained within vessels but rather flows freely in the body cavity. Gas exchange occurs through diffusion across the body wall.
Because they are parts of phylam Annelida as I have read