What does Phylum cnidaria have instead of a circulatory system?

Cnidarians have a hydrostatic skeleton, this means the body is supported by the liquid that fills it. They have a central cavity surrounded by two layers of tissue, the ectotherm and endotherm. The jellyfish has no circulatory system but a nervous system. It has some muscle fibers controlled by the network of nerves. IT has no brain to coordinate its reactions.