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A mixing of germ plasm in sexual reproduction or some other agencies produce congenital variations; natural selection acting upon the numerous progeny selects the best of the new variations, and heredity preserves and hands them down to posterity. All students of whatever school recognize the force of this principle and look upon natural selection as an efficient agency in machine building.
Mendelian phenomena of inheritance, confirmed and extended by numerous workers with plants and animals, prove that in many cases portions of the streams of germ plasm that combine to form the hereditary content of organisms may retain their individuality during embryonic and later development, and that they may emerge in their original purity when the germ-cells destined to form a later generation undergo the preparatory processes of maturation.
"Still," considered Kennedy, "there might have been something latent in her family germ plasm back of the time through which you could trace it?" Dr. Crafts shrugged his shoulders. "There often is, I must admit, something we can't discover because it lies too far back in the past." "And likely to crop out after skipping generations," put in Maude Schofield.
But it is not so easy to see how this germ plasm can undergo variation. The conditions which surround the individual would affect its body, but it is not easy to believe that they would affect the germinal substance.
It was evident merely by shaking hands with Burroughs that he thought both the Athertons and the Burroughses just the right combination. He was one of those few men against whom I conceive an instinctive prejudice, and in this case I felt positive that, whatever faults the Atherton germ plasm might contain, he had combined others from the determiners of that of the other ancestors he boasted.
He writes as from a palely pure tomorrow when mankind shall have reached such a state of complete uniformity of soul, mind and body, that "only a particular inquiry will determine a man from a woman, though it may fail to determine a fool from a man." Tomlinson's imagined nation of the future is "as loyal and homogeneous, as contented, as stable, as a reef of actinozoal plasm."
Probably no one, however, holds this position to-day, and it is the general belief that the germ plasm may be to some slight extent modified by external conditions. Of course, if such variations do occur in the germ plasm they will become congenital variations of the next generation, since the next generation is the unfolding of the germ plasm.
Is there, he asks, a material bond, a bodily, living, and enduring tie, between human beings of all lands and all ages? He finds a proof that there is such a bond in the researches of Weismann and in that writer's theory of the germ plasm, which has now become classic.
With exceptions on both sides, we find that the non-moving microbes generally feed on inorganic matter, which they convert into plasm; the moving microbes generally feed on ready-made plasm on the living non-movers, on each other, or on particles of dead organic matter. Now, inorganic food is generally diffused in the waters, so that the vegetal feeders have no incentive to develop mobility.
The nature must be deeply affected before a change in the person is registered. Personality is not synonomous with inherited disposition; but it bears a similar relation to nature as inherited disposition does to acquired habit. It is to nature what character is to action. It is to nature what in Weismann's theory the germ plasm is to the somatic cell.
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