Pangenesis

Pangenesis, a working hypothesis proposed by C. Darwin ('Changes in Animals and Plants under Domestication') to explain the mechanism of hereditary transmission. The occasion was the need to specifically represent: 1) how a trait of a remote ancestor reappears in offspring (atavism); 2) acquired traits (e.g. through exercise) are transmitted to offspring (Darwin was convinced of this); 3) how an organism can be formed equally from sexual products and buds; 4) how hybrid forms, when developed through grafts, can bear traits of both plants; 5) how removed parts of organs are restored through regeneration. The essence of the hypothesis of P., which generalizes these facts, lies in the fact that 'not the organism as a whole reproduces its kind, but each unit reproduces one like itself.' According to Darwin, this is accomplished by means of the smallest germs {gemmules, see}, separated during development and life by all cells of the body, spreading throughout the organism, accumulating in the buds and sexual organs, and being the true cause of the appearance of similar units of the organism in the next generation. The transmission of gemmules in a dormant state, like seeds in the ground, explains the phenomena of atavism. In the hypothesis of pangenesis, Darwin brings together the phenomena of growth and reproduction—an idea expressed by the ancients (Hippocrates) and developed by Buffon. The hypothesis of P., despite the fact that it is currently abandoned, is valuable because hereditary substance is represented in it for the first time in the form of numerous individual hereditary units—an idea on which modern genetics is based. About 20 years later, de Vries in his theory of 'intracellular P.' suggested that all hereditary properties of an organism are represented by special particles, called by him pangenes, contained in the nuclei of cells in an inactive state: some of them leave the nucleus for the cell plasma and determine its properties. Thus, according to de Vries, the term 'pangen' originally implied an intranuclear, and ultimately a cytoplasmic, hypothetical unit of the cell.