(4) August Weismann gave thegerm plasm theory, accordingto which inheritance onlytakes place by means of thegerm cells (gametes such asegg cells and sperm cells). Othercells of the body (somaticcells) do not funct ion asagents of heredity. Weismannwas considered as the secondmost notable evolutionarytheorist of the 19th centuryafter Charles Darwin.