Many Platyhelminthes & Nematodes are parasitic and therefore many do NOT have complex digestive systems

Digestion

Platyhelminthes

(AKA: Flatworms)

Lab station diagram

Nematode

(AKA: Roundworm)

Lab station diagram

Some are carnivores and eat off of other animals.

Nutrition & Food Getting

Nutrition & Food Getting

Some simply absorb nutrients off of the tissues and organs inside of hosts.

Nutrition & Food Getting

Some simply suck fluid from hosts

Depending on the species...

*some digest food Extracellularly (either     outside of their cells or even outside their body)

*some digest food Intracellularly

*some can do both

DIGESTION

As you can see, depending on the species, they can be either carnivorous or saprophagous!

(Some juveniles are herbivorous and eat algae)