These similar creatures, which belong to the cephalopod molluscs, and they have 3 hearts: the first function is to pump blood throughout the body, while the other two "Gill hearts" push it through their gills.
Although it is not formally called the "heart," the aortic arch of earthworms makes the same function and is usually called so for the sake of simplicity. From a Womble is 5 arc-hearts, separated into segments and exporting the blood throughout the body.
People know that this horrible creature in the body of the beating hearts? Do hagfish have as many as 4 hearts, one of which is three-chamber and most importantly, and the remaining three serve as an auxiliary "pump".
See also: three amazing animals that can talk
Yes, the world really have such people who have in the body beating hearts. All this because of heart transplants, when a person is implanted one additional heart.