What was Lamarck's idea about evolutionary theory

Lamarck is best famed for his Theory of Inheritance of noninheritable Characteristics, initial given in 1801 (Darwin's initial book addressing survival was printed in 1859) : If associate degree organism changes throughout life so as to adapt to its atmosphere, those changes ar passed on to its offspring.

If an organism changes during life in order to adapt to its environment, those changes are passed on to its offspring.