though vastly slower, remain still deathless. Thus life is a really unbroken continuum from its beginning to its end and we are all connected, as it were, by direct physical participation with the life of our progenitors. Each individual produces a few germ cells that reach the goal of maturity and many somatic cells doomed to death; and in the next generation each repeats the same process. Some flagellate spores, for example, when they divide, lose only the flagellum, which each new individual has to reproduce for itself and this is the rudiment of the corpse that in the higher forms of life becomes indefinitely more bulky and complex; while underneath all this increasing punctuation by death, as it developed, the old plasmal immortality still persists. On the other hand, all forms of fission and agamic budding, so common a method of reproduction in plants and often found in simpler forms of multicellular animal life, such as sponges and coelenterates, are reminiscent of the protozoan fashion. Thus we see that death came into the world not by reason of sin, as theology teaches, but because of differentiation. As cells acquired the power to produce more and more specialized organs and functions they lost the power to reproduce the entire body and they lost it progressively--almost in exact proportion as their power of multiplication became specific. Thus, as we should expect, we find in the early stages of this differentiation cells that can be influenced toward the old general or the new and more specific powers of reproduction. Yet back of all the fact remains that life itself is essentially perdurable and that we can explain death better than we can explain life. Death is thus not necessary or universal but is derived and is, in a sense, a product of slow development; and we can conceive a stage of evolution in which natural death did not occur at all but was always due to external accidents. Indeed, Weismann goes so far as to say that the difference between the germ and the soma is so great that the latter, with all its fortunes, has little or no influence upon the former; and by his doctrine that acquired traits and qualities are not inheritable he seems to draw a hard and fast line separating the mortal from the immortal parts or organisms. He also devoted the greatest ingenuity in evolving an intricate scheme of biophores, ids, idants, determinants, etc., inherent in germ cells, in order to explain the phenomena of heredity. His studies have had great influence in directing the attention of investigators to the most elementary structures and functions of germ plasm and the remarkable changes within cells that occur in the very earliest stages of embryonic development; while, as we shall see, many of the most recent researches have been directed, since his work was done, to the conditions under which somatic cells in different tissues of the animal body can be made to proliferate and grow, under carefully controlled conditions, more