As a matter of fact however, the coming struggle was foreshadowed in a paper read by Weismann at the meeting of the Association of the German Naturalists at Salzburg, two years earlier, in 1881.
This paper was entitled “The Duration of Life,” and the subject was still further developed in an academic lecture, in 1883, on “Life and Death.” These two biological contributions not only indicated the foundations of Weismann’s theory, but they threw a very brilliant light in certain very dark places. Weismann not only took up, but he solved the hitherto obscure question of the origin of death.
Johannes Muller had, as early as 1840, rejected the prevailing hypothesis which held the death of animals to be due to “the influences of the organic environment, which gradually wear away the life of the individual.” Muller argued that if this were so “the organic energy of an individual would steadily decrease from the beginning.” Everybody knows, however, that in spite of the wear and tear caused by the “environment,” be it organic or inorganic, the volume of life increases, until a certain stage is reached in all animals. But Muller had failed to fill the gap his criticism had created.
This problem Weismann solved by analysing the methods of reproduction among animals. These generally speaking are two; sexual, and non-sexual or, as it is sometimes termed, a-sexual. This latter form is the mode that prevails at the bottom of the organic scale--among the protozoa, animals consisting of a single cell. This method has a variety of forms which are classified by Haeckel as (1) self-division; (2) formation of buds; (3) the formation of germ-cells or spores. We shall here deal only with the first, self-division, or fission, which is the most universal of all methods of propagation, being the progress by which the individual cells which compose all the higher animals multiply themselves. This is the method vital to Weismann’s theory and the other two are no more than distinct modifications of fission.
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.
