The manipulation of food from the environment to the mouth in a cnidarian is made possible because of

Many Cnidarians eat small planktonic animals that they catch with their tentacles and stinging nematocysts. They don't go "hunting" but have to wait for their prey to blunder into the tentacles. Once this has happened other tentacles are brought to the prey to secure capture and subdue it with more stinging cells. The larger jellyfish can capture small fish this way too.Cnidarians have tentacles that are around the mouth which help them to catch and eat food, they use their nematocysts to fire out barbs or toxins at the prey to kill, injure, or paralyze them. Almost all cnidarians are carnivores, and feed mainly on shrimps, amphipods, plankton, and any other small organism that gets trapped in the tentacles. Once the prey is entangled in the discharged nematocysts it is moved into the mouth and digested in its gastrovascular cavity.