We therefore see that the embryo, or the individual, is formed from one, and one only, of the first products of the division of the fertilised germ-cell, the rest of these products forming the other body tissues. This idea of the continuity of the germ-plasm is the greatest contribution of modern embryological research. It is quite fundamental, and no clear understanding of what is involved in the making of a man is possible without it. It teaches us that the line of ancestry and heredity is from one generation of germ-cells to another, directly, and never through the individual from the embryo, which, indeed, is a mere side product in the continued chain of events. The individual is practically the trustee of the germ-cells, but not their maker. No embryo, and no individual, ever made germ-cells; the latter existed first. The object of the embryo is obviously to protect and nourish the germ-cells which have been placed within it, so that they may be available in due time for the production of further germ-cells, and so for the continuity of the race. Hence it is the all-pervading truth of natural selection that the interest and survival of the individual is almost of no account; that of the species or the race being the paramount consideration. Once these facts be grasped there is no longer any difficulty in understanding why the process of reproduction in any given species always results in the formation of embryos which resemble each other in all the main characters of their species. It could not be otherwise, because they come from portions of identically similar material, a common germ-plasm. In other words, the individual inherits nothing from its parents. He merely receives in his turn the material inheritance in the germ-plasm which was there a generation before him. In so far as there has been no germinal variation he and they will be similar. Hence the common observation that the child resembles the parent. True, so he does; but not because he gets his characters from them, but simply because he and they obtain their characteristics from a common source. To many this thought will be, perhaps, a new one. It is one of the most interpreting ideas which science has given us, and in its absence no real grasp of the origin of the physical, mental, and other characters if there be any, of the embryo can be understood. The present writer has elsewhere summarised this thought as follows:-- "Man is composed partly of characteristics, which are derived from pre-existing germ-cells, and over the possession of which he has no control whatsoever. Be they good, bad, or indifferent, these characteristics are his from his ancestry in virtue of his inheritance. The possession of these characteristics is to him a matter of neither blame nor praise, but of necessity. They are inevitable."