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Updated: June 18, 2025
The orthodoxy of science, therefore, must be held as giving at any rate a provisional support to Professor Weismann, but all of them, including even Professor Weismann himself, shrink from committing themselves to the opinion that the germ-cells of any organisms remain in all cases unaffected by the events that occur to the other cells of the same organism, and until they do this they have knocked the bottom out of their case.
"In such a case we have only to assume that the climate which is unfavourable, and the nutriment which is insufficient for horses, affect not only the animal as a whole but also its germ-cells. This would result in the diminution in size of the germ-cells, the effects upon the offspring being still further intensified by the insufficient nourishment supplied during growth.
On another page he writes: "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.
If the mere anxiety connected with an ill-healing wound inflicted on but one generation is sometimes found to have so impressed the germ-cells that they hand down its scars to offspring, how much more shall not anxieties that have directed action of all kinds from birth till death, not in one generation only but in a longer series of generations than the mind can realise to itself, modify, and indeed control, the organisation of every species?
We cannot so test every sixpence given us in change as to be sure that we never take a bad one, and had better sometimes be cheated than reduce caution to an absurdity. Moreover, we have seen from the evidence given in my preceding article that the germ-cells issuing from a parent's body can, and do, respond to profound impressions made on the somatic cells.
The body, in a historical sense, grew up around the germ-cells, taking over functions a little at a time, until in the higher animals nutrition and other activities and a large part even of the reproductive process itself is carried on by body-cells.
Pangenesis, with its attraction of gemmules from all parts of the body into the germ-cells, and the free circulation of gemmules in the offspring till they hit upon or are attracted by the particular cell or cells, with which alone they can readily unite, seems a less feasible theory and less in conformity with the whole of the facts than an hypothesis of germ-continuity which supposes that the development of the germ-plasm and of the successive self-dividing cells of the body proceeds from within.
Of course neither Spencer nor any one else, until the re-discovery of Mendel's work, had any notion at all of the remarkable fashion in which these units are treated in the process whereby germ-cells are prepared for their great destiny. The rule, as we now know, is that one germ-cell contains any given unit, while another does not.
How can this use of special muscles stamp itself upon the germ-cells in such a way that the offspring will have these special muscles enlarged?
I did so with the less unwillingness because I saw that no one else appeared to understand the theory, and that even Mr. Darwin's warmest adherents regarded it with disfavour. If Mr. Darwin means that every cell of the body throws off minute particles that find their way to the germ-cells, and hence into the new embryo, this is indeed difficult of comprehension and belief.
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