By the development of this process, multicellular metazoa arose from the colonies of similar protozoa, and at length culminated in the higher animals and man.

If we examine the human body, its origin and end, in the light of these facts, we shall see that a comparison between the simple immortal protozoa and man leads us to the result that man himself, or at least a part of him and that the most important, is immortal.

When we turn to the starting point of human development, we find an egg cell and a spermatozoon, which unite and whose nuclei intermingle. Thus a new cell is produced. This process is similar to the conjugation of two unicellular beings, such as two acinetiform infusoria, one of which, the female (੐), is larger than the other, the male (੒). This difference of size in the conjugating cell is, however, without importance.

From this double cell produced by conjugation many generations of cells arise by continual cell division in divergent series. Among the infusoria these are all immortal, but many of them are destroyed, and only a few persist till conjugation again takes place. The same is the case with man. Numerous series of cell families arise, which are all immortal: of these but few - strictly speaking, only one - live till the next period of conjugation and then give the impulse which results in the formation of a new diverging series of cells. The difference between man and the infusorian is only that in the former the cells which originate from the double cell (the fertilized ovum) remain together and become differentiated one from another, while in the latter the cells are usually scattered but remain alike in appearance, etc.

The seeds of death do not lie, as Weismann appears to assume, in the differentiation of the cells of the higher animals. On the contrary, all the cell series, not only those of the reproductive cells, are immortal. As a matter of fact all must die; not because they themselves contain the germs of death and have contained them from the beginning, but because the structure which is built up by them collectively finally brings about the death of all. The living plasm in every cell is itself immortal. It is the higher life of the collective organism which continually condemns countless cells to death. They die, not because they cannot continue to exist as such but because conditions necessary for their preservation are no longer present.

Thus, while the cells are themselves immortal, the whole organism which they build up is mortal. The complex inter-dependence between the single cells, which, since they have adapted themselves to division of labor, has become necessary, carries with it, from the beginning, the seeds of death. The mutual dependence ceases to work, and the various cells are killed.

The death of the individual is a consequence of the defective precision in the working of the division of labor among the cells. This defect, after a longer or shorter time, causes the death of all the cells composing the body. Only those which quit the body retain their power of living.

Of all those countless cells which, in the course of a lifetime, are thrown off from the body, only one kind is adapted for existence outside the body, namely, the reproductive cells.

Among the lower animals the reproductive cells often leave the body of their parents only after the death of the latter. This is not the case in man.

All the cell series which do not take part in the formation of reproductive cells, as well as all the reproductive cells without exception, or with only a few exceptions, die through unfavorable external conditions; just as all, or almost all, of the infusoria which arose from the double cell die before they can conjugate again.

At times, however, some of the infusoria persist till the next period of conjugation, and in the same way, from time to time, some of the human reproductive cells succeed in conjugating, and from them a new individual arises.

A man is the outgrowth of the double cell produced from the conjugation of two human reproductive cells, and consists of all the cells which arise from this and remain in connection with each other. The human individual originates at the moment of the mingling of the nuclei of the reproductive cells; and the details of this mingling determine his individual peculiarities.

The end of man is manifestly to preserve, to nourish, and to protect the series of reproductive cells which are continually developing within him, to select a suitable mate and to care for the children which he produces. His whole structure is acquired by means of selection with this one object in view, the maintenance of the series of reproductive cells.

From this standpoint the individual loses his significance and becomes, so to speak, the slave of the reproductive cells. These are the important and essential and also the undying parts of the organism. Like raveled threads whose branches separate and reunite, the series of reproductive cells permeate the successive generations of the human race. They continually give off other cell series which branch out from this network of reproductive cells, and, after a longer or shorter course, come to an end. Twigs from these branches represent the human individuals, and any one who considers the matter must recognize that, as was said above, apart from the preservation of the reproductive cell series the individuals are purposeless.

It is on this basis that the moral ordering of the world must place itself if it is to stand on any basis at all. It is an easy and a pleasant task to interpret the facts of history from this standpoint. Everything fits together and harmonizes, and each turn in the historical development of civilization when observed from this point of view acquires a simple and a clear causality.

I cannot enlarge on this topic, engaging as it is, but here a further question obtrudes itself. May there not be some connection between the actual immortality of the germ cells, the continuity of their series and the importance of the part they play, and the origin of the idea of an immortal soul? May not the former have given rise to the latter?