Asked by: Ben Harrison, Cranleigh
Earthworms (Lumbricus terristris) are annelids and have a very simple nervous system, with a single nerve cord running the length of the body and side branches for each segment and no brain. If an annelid is cut in two, they can regenerate to some degree, and in some species you can even end up with two worms. The common earthworm, however, will only regenerate from the tail end; the head end always dies. The tail end that is left will still to be able to sense along its entire body, but the most sensitive sensory structures are located in the front-most segment, so its senses will be somewhat limited until this regenerates.