Nor is this all. The studies made by contemporary biologists, and notably by the Russian biologist Janicki, on sexual reproduction[65] have explained how this method of reproduction safeguards the homogeneity of the germ plasm in an animal species, and how it unceasingly renews the mutual contacts among the individual members of a race. Janicki writes: "The world, if I may say so, has not been broken up into a mass of independent fragments, which then, for ever isolated one from another, ... must strike out for themselves on straight courses, with only side branches. On the contrary, owing to bi-sexual reproduction (amphimixis), the image of the macrocosm is ... reflected as a microcosm in each part; and the macrocosm resolves itself into a thousand microcosms.... Thus the individuals, while remaining independent, are materially and continuously interconnected, like strawberry plants whose runners are joined together.... Each separate individual develops, as it were, through an invisible system of rhizomes (subterranean roots) which unite the germ substances of countless individualities."--Thus it has been calculated that in the twenty-first generation, in five hundred years let us say, and supposing an average of three children to each couple, the posterity of a single couple will be equal in number to the entire human race. It may, therefore, be said that each one of us has within him a small portion of the living substance belonging to every one of the human beings that were living five hundred years ago. Consequently it is absurd that anyone should wish to restrict an individual, be he whom he may, within the category of a separate nation or race. Let us add that thought, too, propagates itself throughout mankind, in like manner with the germ plasm. Every thought, once expressed, leads in the human community a life independent of its creator; undergoes development in other minds; and has, like the germ plasm, an immortal life. So that, in humanity, there is neither true birth nor true death, whether material or spiritual. Empedocles, of old, realised this, for he said: "Yet another truth will I tell unto thee. Not a mortal thing is truly born, and death the destroyer is not the end. There is nought but intermixture and exchange of what is intermixed. But among men it is customary to term this 'birth.'" Humanity, therefore, materially and spiritually, is a single organism; all its parts are intimately connected and share in a common development.