What example did Lamarck give for his theory of acquired traits?

Lamarck illustrated his theory of acquired traits using the example of the giraffe. He proposed that ancestral giraffes stretched their necks to reach higher leaves, and this effort resulted in longer necks over generations. According to Lamarck, these acquired characteristics were then passed on to their offspring, leading to the longer necks observed in modern giraffes. This idea, however, has been largely discredited in favor of Darwinian evolution by natural selection.