Winter kills most plants, which, generally speaking, require warmth, moisture, and sunlight for their life. The luxuriance of the tropics tapers off toward the poles. But seeds have amazing vitality. Neither the intense cold and prolonged darkness of the extreme latitudes, nor the aridity of the desert, kills them, while in animals the cells of the male or female gender are the last in the body to die.
Take heed how nature values these male and female reproductive elements, so that physiologists are led to exclaim that our bodies are but mere appendages of the sex cells, which, in a manner, seem to have some tendency toward immortality, at least they are the only cells within us which persist after our deaths in posterity.
The child within the womb is an endo-parasite; while suckling it is an ecto parasite.
Through its whole subsequent life it is the perpetuation of the lives of the sex-cells of its parents, with increments of nutrition added to these original unit masses.
A philosopher once said, "I have never seen a child, without thinking it will become aged, nor a cradle without seeing a grave". Deeper penetration might have shown him as well that something from our ancestors is still alive within us, that we cannot sift out inheritance, and that each parent permeates every cell.
In the lowly Protozoans each animal gives rise to successive generations by simply dividing itself into two; each half lives, and these eventually subdivide into others, and so on in endless fashion.
Weissmann thus speaks Of the "Immortality of the Protozoa," for there are no corpses! In this sense, also, those of our reproductive cells which take part in impregnation escape the death which overtakes the rest of the body, develop into new organisms, and form new cells which retain the remotest ancestral characteristics.
Outside of what mere faith may lead us to think, no facts point so strongly in the general direction of immortality as the history of the sex cells, which seem to be formed for resisting death and continuing existence. Thus man does not altogether "run down like a clock and stop forever".
Agriculture without an abundance of good seed would be a waste of time, as stock farming would be without good progenitors.
According to the degree of our unsoundness or healthfulness this is either appalling or encouraging, and when we consider how closely the sexual life is related to the interests of mankind it is hard to see how the problems of ethics can be extended into large treatises and systems with so little reference to its most nourishing elements.