This theory is given by German biologists August Weishmann. According to this theory, “in living organisms, there are two types of cells:
- Somatic cells
- Germinal cells.
Weishmann proved that only the changes in germinal cells are inherited from parents to offspring but not the changes in somatic cells. For this, Weishmann cut the tail of mice for 20 generations and measured the tails in each generation. In all generation of the mouse, he found the shape and size of this tails similar or equal. This was because there were changes in only the somatic cells not in the germinal cells.