How did Lamarckism explain the development of webbed feet in water birds?

Lamarckism, proposed by Jean-Baptiste Lamarck, suggests that physical changes acquired by an organism during its lifetime—often due to environmental needs—can be passed on to its offspring.12

Regarding water birds, Lamarck theorized that the development of webbed feet was a direct result of the birds' need to swim to find food. According to this doctrine, when these birds sought to rest or feed on water, they habitually spread their toes to navigate the surface. This repeated stretching of the skin between the toes caused the tissue to become accustomed to the tension, eventually forming the webbed structure. Lamarck argued that these material alterations, driven by the birds' new habits and efforts to satisfy environmental needs, were then inherited by subsequent generations.2

While these ideas were influential in the 19th century, they have been discredited by modern genetics, as there is no biological mechanism for such acquired somatic changes to be transmitted to an organism's sex cells.12