The facts invoked by _Weismann_ against the heredity of acquired characters lose nothing of their weight by this, for the influence of crossing (conjugation) and selection transforms the material organic forms in an infinitely more rapid and intense manner than individual mnemic engraphias. The latter, on the other hand, furnish the explanation of the mutations of _de Vries_, which appear to be only sudden ecphoria of accumulated long engraphic actions. The way in which _Semon_ studies and discusses the laws of the mneme in morphology, physiology and psychology, is truly magisterial, and the perspective which opens out from these new ideas is extensive. The mneme, with the aid of the energetic action of the external world, acts on organisms by preserving them and combining them by engraphia, while selection eliminates all that is ill-adapted, and homophony reëstablishes the equilibrium. The irritations of the external world, therefore, furnish the material for the construction of organisms. I confess to having been converted by _Semon_ to this way of conceiving the heredity of acquired characters. Instead of several nebulous hypotheses, we have only one--the nature of mnemic engraphia. It is for the future to discover its origin in physical and chemical laws. I must refer my readers to _Semon's_ book, for this volume of 343 pages, filled with facts and proofs, cannot be condensed into a few paragraphs. =Each Cell bears in itself Ancestral Energy.= As we have already seen, the germinal, cells are not the only ones which possess the energies of all the characters of the species. On the contrary it becomes more and more certain, from further investigation, that each cell of the body bears in itself, so to speak, all the energies of the species, as is distinctly seen in plants. But in all the cells which are not capable of germinating, these energies remain incapable of development. It results that such energies, remaining virtual, have no practical importance. In an analogous sense we may say that all the cells of the body are hermaphrodite, as all germinal cells, for each possesses in itself the undifferentiated energies of each sex. Each spermatozoid contains all the energies of the paternal and maternal ancestry of man, and each egg those of the paternal and maternal ancestry of woman. The male and the female are only the bearers of each kind of germinal cells necessary for conjugation, and each of these bearers only differs from the others by its sexual cells and by what is called correlative sexual differences. But we must not forget that the germinal cells themselves are only differentiated at a certain period in the development of the embryo; they are thus hermaphrodite originally and only become male and female later.