How is a flatworm tegument different from a roundworm cuticle?

In flatworms (Platyhelminthes), they have a tegument which is a living outer layer. As a parasite living in the gut of the host, it wants to absorb nutrients from the medium around them, therefore it is important that they have a metabolically active outer layer for vital activities such as absorbtion, protection and secretion.

On the other hand, roundworms (Nemathelminthes) have a rigid outer cuticle which works with the muscles to create a hydroskeleton. It has a digestive system which starts with a mouth and ends at the anus.

This is significant from a medical point of view as this characteristic, having a cuticle

or tegument determines what kind of drug is used to treat the parasite. Some drugs can destroy the living outer layer of a tapeworm, while other drugs are ingested by the roundworms which then attacks the lining of their gut.