Some scientists disputed Darwin’s claim, arguing that the small, weak creatures weren’t capable of moving such massive amounts of material to the surface. Darwin responded to the criticism by conducting a more careful experiment. This time rather than measuring the rate at which objects were buried, he weighed all the worm castings thrown up to the surface each day. He found that in a single acre of farmland over eleven tons of earth passes to the surface through the bodies of worms every year! In the words of Charles Darwin: “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.”