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Updated: May 22, 2025
Do you still believe in the infallibility of the germ-plasm? Has the fan brought you ill-luck? The fact is, Arn, ever since your return from China you've been a strange bird!" It was Effinghame's turn to laugh. "Don't say another word." The doctor was vivacious in a moment and poured out wine. They both lighted cigars. Slowly puffing, Arn took up the fan and spread it open. "See here!
This enables him to explain heredity by his theory of the "Continuity of the Germ-plasm." Parent and offspring are alike successive products or offshoots of this persistent germ-substance, which obviously would not be correspondingly affected by modifications of parts in parents, and so would render the transmission of acquired characters impossible. Mr.
The effect will not be an exact reproduction of the cause, nor will the change in the germ-plasm, provoked by a certain modification of a certain part of the soma, determine a similar modification of the corresponding part of the new organism in process of formation, unless all the other nascent parts of this organism enjoy a kind of immunity as regards C: the same part will then undergo alteration in the new organism, because it happens that the development of this part is alone subject to the new influence.
We have already seen that these questions are left unsolved by the one-birth theory of Christianity and of Judaism. But this theory of "continuity of the germ-plasm" pushes the question of heredity to the door of Reincarnation.
Hence it follows that the transmission of acquired characters is an impossibility, for if the germ-plasm is not formed anew in each individual, but is derived from that which preceded it, its structure, and, above all, its molecular constitution, cannot depend upon the individual in which it happens to occur, but such an individual only forms, as it were, the nutritive soil at the expense of which the germ-plasm grows, while the latter possessed its characteristic structure from the beginning, viz., before the commencement of growth.
There are the problems of germ-plasm, and its transmission; the effect on it, if any, of the body, and the reaction of the body to its environment. There are also the catalysers of which we have spoken, with many problems associated with them, and throwing a possible and unexpected light on the vexed question of Vitalism and the Conservation of Energy.
The importance of use and disuse, and the transmissibility of their effects, would seem to supply a factor essential to evolution. Weismann has done good service in emphasizing the stability of the germ-plasm. Evolution is always slow, and, for that very reason, sure. If these conclusions are correct, they have an important practical bearing. Struggle and effort are essential to progress.
No one would deny, I think, that the continuity of the germ-plasm offers the best and most natural explanation of heredity; and that variations could be produced by the influence on the germ-plasm of external conditions seems entirely probable. But when we consider the aggregation of these variations in a process of evolution, his theory seems unsatisfactory.
According to Weismann, the individual parts and characteristics of the organism are represented in the germ-plasm, not in finished form, but as “determinants” in a definite system which is itself the directing principle in the building up of the bodily system, and with definite characteristics, which determine the peculiarities of the individual organs and parts, down to scales, hairs, skin-spots, and birth-marks.
Let us attempt to state simply but accurately what biologists mean in regarding the individual as primarily the host and servant of something called the germ-plasm.
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