Water enters this system through the madreporite , passes down a stone canal into a ring canal, and then into radial canals.
Water enters the water vascular system of an echinoderm through the madreporite, which is a sieve-like structure located on the aboral (upper) surface of the animal.
From there, the water passes down a stone canal into a ring canal that encircles the mouth. The water flows into radial canals that extend along the arms of the echinoderm.
The tube feet of echinoderms are powered by the water vascular system. Water pressure in the tube feet allows them to extend and contract, enabling the echinoderm to move around.
complete question:
Water enters this system through the _____ , passes down a stone canal into a ring canal, and then into radial canals.