August Weismann was a German biologist known for his contributions to the understanding of heredity and evolution. He is best recognized for his theory of the germ plasm, which proposed that only the genetic material in reproductive cells (or germ cells) is passed on to the next generation, while somatic cells do not contribute to inheritance. This idea challenged the prevailing views of his time and laid the groundwork for modern genetics. Weismann's work also included studies on Darwin's theory of evolution and the role of natural selection. He conducted experiments on animal regeneration and emphasized the importance of the environment in shaping species. His ideas influenced later scientists, including Gregor Mendel, whose work on inheritance complemented Weismann's theories.