In this supposition that the organic molecules, which, in the mixture of the seminal liquors of the two individuals, represent the sexual parts of the male, can alone serve for a base to the organic molecules proceeding from every part of the female, and those peculiar to the female sex as a base to them which are extracted from the male, we might conclude, that the sexual part of the male infant is formed of the organic molecules of the father, and from those of the mother, for the rest of the body: and that, on the contrary, the female partakes of its mother only in sex, and takes the rest of its body from its father. Boys, therefore, ought, excepting the parts of the sex, to have a greater resemblance to their mother than to their father, and girls more to the father than to the mother; but this consequence is not, perhaps, conformable to experience. By considering, under this point of view, generation by sexes, we should conclude it to be the most general mode of reproduction, as it is in fact. Beings, whose organization is the most complete, as animals, whose bodies compose a whole, which can neither be separated nor divided, and whose powers are con-centered to one single point, can only reproduce by this mode; because they contain only particles which resemble each other, and whose union can only be made by different particles, furnished by another individual. Those where organization is less perfect, as that of vegetables, whose bodies may be divided and separated without being destroyed, can be reproduced by other modes. First, because they contain dissimilar particles; secondly, because their forms not being so determinate and fixed as that of animals, the particles may supply the functions of each other, and change according to circumstances; as we see roots become branches, and shoot out leaves when exposed to the air, which causes that the vegetable particles obtain a local establishment, become fixed, and are enabled to multiply, by various modes. It will be the same with animals, whose organization is less perfect, as the fresh water polypus, and others, which can reproduce by division of their parts. These organized beings are not so much a single animal, as a number united under one common covering, as trees are composed of a multiplicity of young trees, (see Chap, II.) Pucerons, which engender singly, also contain dissimilar particles, since, after producing their young they change into flies which do not produce at all. Snails communicate mutually these dissimilar particles, and afterwards they both produce. Thus, in all known matters of generation, we see that the requisite union of organic particles, can only be made by the mixture of different particles, which serve as a basis capable of fixing their motions.