Reproduction appears in the history of life even before sex manifests itself. The lower forms of animal and plant life oftener produce themselves without the aid of sex, and some authorities have argued that the presence of sex differentiation serves rather to check active propagation rather than to increase it. If quantity, without regard to quality or variation, be the object of Nature, then that purpose would have been better served by withholding sex-differentiation than by evolving it. As Professor Coulter, a leading American botanist, has well said: "The impression one gains of sexuality is that it represents reproduction under peculiar difficulties." To those who find it difficult to assimilate this somewhat startling idea, we now present a brief statement of the infinitely greater facility toward reproduction manifested by living creatures lacking in sex-differentiation as compared with those possessing it. It is seen that bacteria among primitive plants, and protozoa among primitive animals, are patterns of very rapid and prolific reproduction, though sex begins to appear in a rudimentary form in very lowly forms of life. A single infusorian becomes in a week the ancestor of millions, that is to say, of far more individuals than could proceed under the most favorable conditions from a pair of elephants in five centuries; and Huxley has calculated that the progeny of a single parthenogenetic aphis, under favorable circumstances, would in a few months outweigh the whole population of China. It must be noted, however, that this proviso "under favorable circumstances" reveals the weak point of Nature's early method of reproduction by enormously rapid multiplication. Creatures so easily produced are easily destroyed; and Nature, apparently in consequence, wastes no time in imparting to them the qualities needed for a high form of life and living. And, even after sex differentiation had attained a considerable degree of development, Nature seemed slow to abandon her original plan of rapid multiplication of individuals. Among insects so far advanced as the white ants, the queen lays eggs at the enormous rate of 80,000 a day during her period of active life. Higher in the scale, we find the female herring laying 70,000 eggs at one period of delivery. But in both of these cases we find the manifestation of that apparently invariable rule of Nature, viz., that A HIGH BIRTH-RATE IS ACCOMPANIED BY A HEAVY DEATH-RATE, whether that high death-rate be caused by natural enemies, wars, or disease.