Metchnikoff was able to discover only two ideal cases of old people in whom his “instinct for death” was well developed. But he believes that as gerontology advances this instinct will not be the exception but the rule and that the very nature of old age as we know it will be radically transformed. At present we know little more of it than the prepubescent child knows of sex or the embryo of its mother’s milk. When the instinct for death is well developed, we shall long for it as we do for sleep when we are fatigued, for old age is The Great Fatigue. Many instincts of the young are reversed and pass over into their ambivalent opposite at a later stage of life; and so the love of life will, in the end, be transformed into the love of death. Both animal and human parents devote their lives to the service of their offspring during the period in which this is necessary; but when the latter are mature, we often find a reversal of this instinct. Perhaps the intense sensitiveness of ova and spermotozoa displayed in the phenomena of chemotaxis and in the marvelous power of regeneration of lost parts among many lower forms of metazoa, and the many phenomena that led Haeckel to call the soul of cells immortal, are lost later as higher, conscious psychic powers develop; and if so, this shows the marvelous transformability of the primitive impulses that dominate simpler forms of life. Thus Metchnikoff is a humanist as well as a scientist. He sets down faithfully what he saw through the microscope, but not content with that ventures to indulge his speculative instincts and tell the world what he thinks his discoveries mean for the practical conduct of life and of mind--and that, too, in more or less untechnical terms that make his ideas accessible to intelligent laymen. For him, as for Plato, “philosophy is the art of preparing for death.” He even urged that “the instinct for death seems to lie in some potential form deep in the constitution of man,” and it was this he sought to develop. The only basis for all modern forms of belief in immortality roots in a platonic reminiscence of the processes of the deathless germ plasm, and from this the old soma and the, no whit less, old psyche have departed as far as possible. Psychic life, too, has its proximate beginnings in the intense vitality of germ plasm and cells and from these rudiments the adult human consciousness has so far developed that our conscious psyche knows no more of it than it does of the migrations or depredations of the phagocytes within the body. Man is the most pathetic of beings because of the two tides whose ebb and flow constitute his life--evolution and de- or in-volution, anabasis and catabasis. He has failed, on account of the action of the intestinal fauna within him, to achieve any adequate sense of appreciation, still less enjoyment of the refluent currents. Man is thus deprived of the nascent period in which this wooing of death is due to arise and does