Final answer:
Tapeworms, a type of parasitic flatworm, have no digestive tract and absorb nutrients directly from their hosts.
Step-by-step explanation:
The type of flatworm that has no digestive tract at all is the tapeworm. Tapeworms are parasitic flatworms that live in the digestive systems of their hosts. They absorb digested food from the host through their body wall instead of having a digestive system of their own. Tapeworms are known for their long, ribbon-like bodies composed of repeating segments called proglottids.