The Theories of Heredity of Nägeli, Weismann, and de Vries

Unaware of Mendel’sMendel, Gregor Johann 1866 paper, NägeliNägeli, Carl von, WeismannWeismann, August Friedrich Leopold, and de Vriesde Vries, Hugo each proposed elaborate theories of heredity in the latter parts of the nineteenth century. NägeliNägeli, Carl von proposed a theory based on micellaemicellae, which were crystalline groups of invisible molecules. Regularly aggregated micellaemicellae formed the idioplasm.idioplasm During fertilizationfertilization, maternal and paternal idioplasmsidioplasm fused and were transmitted to offspring. WeismannWeismann, August Friedrich Leopold proposed a clear distinction between somatic and reproductive cells, with only the latter containing the hereditary material. He denoted the reproductive substance in the germ cells by the term “germ plasmgerm plasm” and proposed that the germ plasmgerm plasm was continuous and could affect the soma plasm, but not vice versa. De Vriesde Vries, Hugo’ theory was based on Darwin’sDarwin, Charles Robert gemmulesgemmulesin Darwin's provisional hypothesis of pangenesis (1868) (which he called pangenspangens) but excluded any transport of these gemmulesgemmulesin Darwin's provisional hypothesis of pangenesis (1868) from the body to reproductive cells. The pangenspangens resided inside the nucleus of every cell.