What did August Weismann’s mouse-tail experiments test?

August Weismann’s mouse-tail experiments were designed to test the theory of the inheritance of acquired characteristics, a central tenet of Lamarckism.123

Weismann sought to determine whether physical mutilations—specifically the removal of tails—could be passed down to subsequent generations. By cutting off the tails of mice for several consecutive generations, he observed that the offspring consistently grew normal tails.23

Through these experiments, Weismann aimed to demonstrate that such acquired physical changes are not inherited, thereby challenging the Lamarckian view that environmental influences or bodily changes in a parent could be transmitted to their progeny. Instead, he argued that the germ plasm remains independent of the body cells (somatoplasm), serving as the stable hereditary material passed from generation to generation. While his experimental design is now viewed as somewhat naive, it served as a critical turning point in biology by shifting the focus toward more rigorous, evidence-based studies of heredity.231