Imagine a worm that has the ability to grow an extra head at its rear end! This weird but real Japanese green syllid worm is called Megasyllis nipponica. The worm can detach this head-like part, which also grows eyes and antennae, and swim away to find another worm of the opposite sex for mating. Scientists have discovered that this strange ability is controlled by the worm's genes, specifically a set of genes called Hox genes. These genes usually help determine the different parts of an animal's body, but in these worms, they play a role in creating the stolon or the detachable part. So instead of just growing one head at its front end, this unique worm can also create another one at its rear end!