Editing August Weismann (section)

=== 1868–1881/82 ===
Weismann started out believing, like many other 19th century scientists, among them [[Charles Darwin]], that the observed variability of individuals of one species is due to the inheritance of ''sports'' (Darwin's term). He believed, as written in 1876, that transmutation of species is directly due to the influence of environment. He also wrote, "if every variation is regarded as a reaction of the organism to external conditions, as a deviation of the inherited line of development, it follows that no evolution can occur without a change of the environment". (This is close to the modern use of the concept that changes in the environment can mediate selective pressures on a population, so leading to evolutionary change.) Weismann also used the classic [[Lamarckism|Lamarckian]] metaphor of use and disuse of an organ.