The generation of man will serve us for an example. I take him in his infancy, and I conceive that the expansion and growth of the different parts of his body being made by the intimate penetration of organic molecules analogous to each of its parts, all these organic molecules are absorbed in his earliest years, and serve only for the expansion and augmentation of his various members, consequently there is little or no superfluity until the expansion is entirely completed; and this is the reason why children are incapable of propagation; but when the body has attained the greatest part of its growth, it begins to have no longer need of so great a quantity of organic particles, and the superfluity, therefore, is sent back from each part of the body into the destined reservoirs for its reception. These reservoirs are the testicles and seminal vessels, and it is at this period that the expansion of the body is nearly completed, when the commencement of puberty is dated, and every circumstance indicates the superabundance of nutriment; the voice alters and takes a deeper tone; the beard begins to appear, and other parts of the body are covered with hair; those parts which are appointed for generation take a quick growth; the seminal liquor fills the prepared reservoirs, and when the plentitude is too great, even without any provocation, and during the time of sleep, it emits from the body. In the female this superabundance is more strongly marked, it discovers itself by periodical evacuation, which begin and end with the faculty of propagating, by the quick growth of the breasts, and by an attraction in the sexual parts, as shall be explained. I think, therefore, that the organical molecules, sent from every part of the body into the testicles and seminal vessels of the male, and into the ovarium of the female, forms there the seminal liquor, which is, as has been observed, in both sexes, a kind of extract of every part of the body. These organical molecules, instead of uniting and forming an individual, like the one in which they are contained, can only unite when the seminal liquors of the two sexes are mixed; and when there is more organical molecules of the male than of the female, in such mixture the produce will be a male; and, on the contrary, when there is more of the female then a female will be the result.