Cnidarian AnatomyAnemone and coral are shaped with one end attached to something solid and the other end with tentacles moving out into the water. The shape is generally called a polyp form. Yes, even coral have that going on. When you think of a coral, you are probably thinking of a hard thing. That hard exoskeleton is what is left of the coral after it dies. When it is alive, hundreds of thousands of cells are alive and waiting for food to come by.
Back to the anatomy of the cnidarians. Anemone and coral are an improvement on sponges. One big improvement is that they have a nervous system. That doesn't mean that they are thinking and planning how to catch food. It does mean that the whole organism can have a coordinated response. That response means if something happens in one part of the anemone, the rest of the anemone can act in a certain way. Maybe a fish is captured on the left side. The right side would then move over to help hold the fish so that it can't escape. They aren't thinking yet. They are acting based on a stimulus.
Specialized TissuesThe cnidarian family also has tissues. Tissues are specially developed groups of cells with one function. There could be tissue to digest food, tissue to help the anemone move, and tissue that helps the anemone stay attached to its rock. All of them work together and have specialized jobs.
The NematocystThere seems to be a theme here regarding special cells. The cnidarians have one called a nematocyst. It's basically a little harpoon or spear that it shoots at passing prey. That harpoon has a poisonous protein that it injects into the prey to stop it from escaping. Nematocysts are also described as stinging cells. Those cells make it dangerous to touch anemone and jellyfish with your bare hands. The poison of some cnidarians can even kill you.
Jellyfish Lake (BBC Video)