I think you are talking about Jean Baptiste Lamarck. He had two big ideas. The first was use and disuse. Parts of the body used extensively to cope with the environment became larger (blacksmith's arm or giraffe's neck). The second was the inheritance of acquired characteristics. Hence, giraffes' necks would get longer.
However, this was all disporved when someone cut the tails off generations of mice and each new generation still had tails.
However, Lamarck was not a total loser. He did claim that evolution explains the fossil record and the diversity in life. And his theory reflected the growing trend that the planet is old. Also, he noted that adapting to the environment was the product of evolution.
