Weismann conducted the experiment of removing the tails of 68 white mice, and those of their offspring over five generations, and reporting that no mice were born in consequence without a tail or even with a shorter tail. In 1889, he stated that "901 young were produced by five generations of artificially mutilated parents, and yet there was not a single example of a rudimentary tail or of any other abnormality in this organ." The experiment, and the theory behind it, were thought at the time to be a refutation of Lamarckism.