Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 22, 2025
The exercise of the muscles might possibly cause such a condition of the blood that the portion of the germ-plasm representing the muscular system of the next generation might be especially nourished or stimulated. Thus an athletic parent might produce more athletic children. But let us imagine twin brothers of equal muscular development.
Professor Weismann's theory is, that at every new birth a part of the substance which proceeds from parents and which goes to form the new embryo is not used up in forming the new animal, but remains apart to generate the germ-cells or perhaps I should say "germ-plasm" which the new animal itself will in due course issue.
If we are to regard the body as a trustee of the germ-plasm, it is evident that the body which carries the germ-plasm with itself to the grave the "immortality of the germ-plasm" being only conditional and at the mercy of the acts of individuals has stultified Nature's end; and it will be a serious concern of ours in the present work to show how, amongst human beings, at any rate, this stultification may be averted, many childless persons of both sexes having served the race for evermore in the highest degree.
In certain plants there is an underground stem or rootstock, which grows perennially, and each year produces a plant from a bud at its end. This underground rootstock would represent the continuous germ-plasm of successive generations; the plants which yearly arise from it would represent the successive generations of adult individuals, composed mainly of somatoplasm.
But it is not demonstrated that in these different cases of hereditary transmission there had been a real influence of the soma of the animal on its germ-plasm.
In later chapters we shall have much occasion, because of their great practical importance in the conduct of woman's life from girlhood onwards, to discuss the physiological and psychological facts which demonstrate overwhelmingly the truth of the view that the individual was evolved by Nature for the care of the germ-plasm, or, in other words, was and is constructed primarily and ultimately for parenthood.
"I believe that heredity depends upon the fact that a small portion of the effective substance of the germ, the germ-plasm, remains unchanged during the development of the ovum into an organism, and that this part of the germ-plasm serves as a foundation from which the germ-cells of the new organism are produced. There is, therefore, continuity of the germ-plasm from one generation to another.
Germ-plasm in the egg is like Humpty-Dumpty on the wall; somatoplasm, like Humpty-Dumpty after his great fall. I use these rude illustrations to make clear one point: Germ-plasm can easily change into somatoplasm, but somatoplasm once formed can never be reconverted into germ-plasm, any more than the fallen hero of the nursery rhyme could ever be restored.
A logical result of the theory is the impossibility of the transmission of acquired characters, since the molecular structure of the germ-plasm is already determined within the embryo; and Weismann holds that there are no facts which really prove that acquired characters can be inherited, although their inheritance has, by most writers, been considered so probable as hardly to stand in need of direct proof.
The mingling of the two produces a germ-plasm and individual differing from both of the parents. Thus, according to Weismann's earlier view, the origin of variation was to be sought in sexual reproduction through the mingling of slightly different germ-plasms. But how did these two germ-plasms come to be different? How was the variation started?
Word Of The Day
Others Looking