If these speculations were true, a change of morphology or functioning, acquired by the body, or somatoplasm, could not possibly be transmitted to the progeny of the organism, for by hypothesis the germ-plasm cannot be affected by external changes, and it is only the germ-plasm contained in the spermatozoon of the male parent, or in the ovum of the female, that shapes and builds the body of the offspring. As if this were not enough, Weismann and his followers argued that the transmissibility of a somatic change to the germ was inconceivable. Why? Because the germ-cells are apparently simple: they are only semi-fluid protoplasmic cell bodies and nuclei, not differing appreciably from the cell bodies and nuclei of the somatoplasm (by hypothesis, it should be noted, the difference is profound). There are no structural connections--no nerves, for instance--which join together the cells of the bodily tissues with the parts of the germ and transmit changes in the former to the latter. How, then, could a somatic change affect the germ so that when the latter developed into an organism this particular change became reproduced? Now this may have seemed a conclusive argument in 1883, but is it so conclusive to-day? We know that the cells and tissues are not isolated particles, but that all are connected together by protoplasmic filaments. We know that specialised nervous tissues are not necessary for the transmission of an impulse from a sensory to a motor surface, but that such an impulse may be transmitted by undifferentiated protoplasm. We know that nerve-cells and nerve-fibres are not structurally continuous with each other but that the impulse leaps across gaps, so to speak. We know that events that occur in one part of the body of the mammal may affect other parts by means of the liberation of a chemical substance, or hormone, into the blood stream. It would be strange indeed if a logical hypothesis capable of accounting for the transmission of a particular change from the soma to the germ could not be elaborated.