Evolution Social and Organic

by Arthur M. Lewis

When a Moneron or an Amoeba reaches a certain size, it begins to pinch in the middle like a tightly-laced corset. This increases until the creature divides into two equal halves. Each of these halves becomes a complete individual which continues to thrive until the next division takes place.

What Weismann observed as the most significant thing about this was that in this process and among these unicellular (single celled) organisms there is no such thing as natural death. Accidental death is wholesale in its proportions, but no Moneron ever dies of old age. Astounding as it may seem to the layman, the race-old, world-wide idea that death is “essential to the very nature of life itself” is here totally and indisputably overthrown.

“I pointed out,” says Weismann, in the second lecture and referring to the first “that we could not speak of natural death among unicellular animals, for their growth has no termination which is comparable with death. The origin of new individuals is not connected with the death of the old; but increase by division takes place in such a way that the two parts into which an organism separates are exactly equivalent to one another, and neither of them is older or younger than the other. In this way countless numbers of individuals arise, each of which is as old as the species itself, while each possesses the capability of living on indefinitely, by means of divisions.”

Among the Metazoa, i. e., multicellular or many celled animals, this immortality of the individual disappears. “Here, also,” says Weismann, “reproduction takes place by means of cell-division, but every cell does not possess the power of reproducing the whole organism. The cells of the organism are differentiated into two essentially different groups, the reproductive cells—ova or spermatozoa—and the somatic cells, or cells of the body. The immortality of the unicellular organism has passed over to the former—the reproductive cells—the others must die, and since the body of the individual is chiefly composed of them, it must die also.”

And so death came into the world, not by sin, as the Genesis legend reports, but through sex; a most astonishing conclusion, it may be, but one from which there is apparently no escape. Immortality still remains, it is true, but it is not the immortality of the conscious self. Positive science, nothwithstanding all its glorious gifts, has dealt a terrible blow to those gorgeous dreams of primitive men and modern mystics; those hopes and longings which have sustained millions of our race in hours of supreme sorrow; a blow which not even the bravest has been able to receive without flinching. The only immortality of which science has any surety is that of these unconscious single cells, which make possible the reproduction of the species.

Weismann, then, divides the cells which compose the bodies of the higher animals, including man, into two distinct kinds; the somatic, or body cells and the germ, or reproductive cells. These germ cells are, so to speak, batteries in which are stored a substance which Weismann calls germ-plasm. A minutely small portion of this germ-plasm from an individual of one sex, mixed with a similar portion from an individual of the other will produce a new individual. But—and here comes the keystone of Weismann’s arch—only a portion of the mixed germ-plasm is used up in the composition of the new individual; the rest is stored away in the germ-cells of the new individual for further reproduction when the time arrives. The only relation that this reserved germ-plasm has with the body cells of the new individual is that it is provided by them with room and board.

Thus, according to Weismann, from generation to generation, there is an unbroken stream of germ-plasm, and this constitutes his celebrated theory of “The Continuity of Germ-Plasm.” Granted this theory as a premise, and Weismann’s conclusions cannot be gainsaid. This germ-plasm being the sole “carrier of heredity,” nothing that happens to the somatic or body cells can be transmitted to the progeny.

Darwin had put forward a theory of heredity which he called “Pangenesis,” which made out a good case for the admission of the Lamarckian factor. According to this theory all the somatic or body cells give forth still smaller cells which he calls “gemmules.” These gemmules are collected, by some process not explained, in the reproductive organs. Here they are in packets, and these “packets of gemmules” are “the carriers of heredity.” One can easily see how by this process the effects of use and disuse would be transmissible for an organ shrunk by disuse would not be capably represented by an efficient delegation of gemmules at the reproductive headquarters.

Speaking of this theory, Grant Allen in his biography of Darwin says, “Let not the love of the biographer deceive us. Not to mince matters, it was his one conspicuous failure, and is now pretty universally admitted as such.” It must be remembered however, that Darwin was fully aware of its purely speculative character and with his usual caution entitled it the “Provisional Hypothesis of Pangenesis.”

Romanes, one of Weismann’s ablest critics, compares Weismann’s theory with Darwin’s, and while he refuses to defend Pangenesis against Weismann’s charge that it is a wholly unsupported speculation, he replies by contending that the germ-plasm theory lives in precisely the same kind of a glass house.