August Weismann was a German biologist and one of the founders of the science of genetics. He is best known for his ‘germ plasm’ theory. Weismann’s early studies were on the hydrozoa, which are small predatory animals which live mostly in the sea.
Weismann’s research on hydrozoa convinced him that the germ cells of animals contain ‘something essential for the species, something which must be carefully preserved and passed on from one generation to another’.
Thus was born the theory of the germ plasm, which he embodied in a book first published in German and then in English. Its essence was the notion that all living things contain a special hereditary substance, the germ plasm.
The general idea is still accepted as valid today, though in place of germ plasm one speaks of chromosomes, genes, and DNA. Weismann’s ideas made him one of the leading biologists of the world.