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.