Absence of circulatory system in Hydra is compensated by

Step-by-step solution

Hydra is relatives of corals and jellyfish. All these species are members of the phylum Cnidaria characterized by symmetrical bodies crowned by 10-12 tentacles and an opening called a gastrovascular cavity. This class of organisms don't have a specialized circulatory system. They have a thin layer of cells which when coming in contact with water absorb the nutrients and oxygen required by the body.