The Mnemic Theory of Heredity

Abstract

IN a review of the third edition of Prof. Richard Semon's well-known book upon this subject, in NATURE of January 18 (p. 371), the reviewer writes as follows:” The mnemic theory, which is based upon a belief in the inheritance of acquired characters, naturally does not appeal to those who deny the possibility of such inheritance. From the point of view of modern embryological research, both of these statements are open to challenge. The founder of this mnemic theory, or memory as a general function of organised matter, has indeed written very little upon the subject, which he first broached in a public lecture in 1870. At the date named, when Prof. Ewald Hering, now of the University of Leipzig, gave his classic address, I imagine that the question of the inheritance or non-inheritance of acquired characters had hardly been raised. By a curious coincidence, it was in the same year that Prof. W. Waldeyer in his researches set up the doctrine of the somatic origin of germ-cells from the germinal epithelium, and obviously this doctrine of the somatic or bodily origin of germ-cells is demanded by the view of an inheritance of acquired characters. The history of embryological research upon the germ-cells during the present century demonstrates clearly that in his researches in the lower vertebrates the writer first established” in 1900” an actual tangible continuity of germ-cells from generation to generation, and the absence of any genetic connection between Waldeyer's germinal epithelium and the germ-cells, that in many other cases these finds have been, and are still being, confirmed by the investigations of other observers, and that Prof. Waldeyer himself some years ago withdrew his former researches in favour of such a continuity of germ-cells as underlying the life-cycle. Indeed, he wrote: “The consequences of this doctrine of the continuity of germ-cells are almost incalculable for every branch of biology;” so that now for animals a fundamental postulate of the doctrine of an inheritance of acquired characters has vanished.