August Friedrich Leopold Weismann (January 17, 1834 - November 5, 1914) was a German biologist. He advocated the germ plasm theory, stating that a multicellular organism consists of germ cells that pass on hereditary information, and somatic cells that perform body functions. The germ cells are not affected by anything the body learns or any ability it acquires during its life, and cannot pass this information on to the next generation, this is called the Weismann Barrier. This eventually led to the rediscovery of Gregor Mendel's work. Weismann also conducted one of the seminal experiments disproving the fallacy of Lamarckianism. By cutting the tails off mice for many generations and seeing that their offspring retained their tails, Weismann demonstrated that the injury was not passed on to the offspring and thus that acquired characteristics are not heritable.