These, like most other possible accounts, must be found in Nature; it even appears, that the females in general contribute more to the support of the species than the males; for though both concur in the first formation of the foetus, the female, who afterwards alone furnishes all that is necessary to its growth and nutrition, modifies and assimilates it more to her own nature, which cannot fail of effacing the impression of the parts derived from the male. Thus, if we would judge deliberately and rationally of a species, the females should be the objects examined. The male gives half of the living substance, the female gives as much, and furnishes besides all the necessary matter for its formation. A handsome woman has almost always fine children; a handsome man with an ugly woman, commonly has children who are still more ugly. Thus, in the same species, there may sometimes be two races, the one masculine, and the other feminine, both of which subsisting and perpetuating their distinctive characters, seem to constitute two different species; and this is the point where it appears almost impossible to fix the term between what naturalists call _species_ and _variety_. Suppose, for example, we should constantly couple he-goats with some sheep, and rams with others; it is evident, that after a certain number of generations, there would be established in the species of the sheep, a breed which would tend greatly towards the goat, and would afterwards perpetuate itself; for, though the first produce with the he-goat would be very little removed from the species of the mother, and would be a lamb and not a kid, nevertheless this lamb would have hair, and some other characteristics of its father. If we afterwards couple the he-goat with these female bastards, the production of this second generation will approach nearer to the species of the father, still nearer in the third, and so on. By this method the adventitious characters would soon prevail over the natural ones, and this fictitious breed might support itself, and form a variety in the species, whose origin it would be very difficult to recognize; therefore what can be done by the influence of the one species on another, may still be more effectually produced by the same species. If strong females have continually only weak males, in course of time, a feminine race will be established; and if very strong males are put to females of inferior strength and vigour, a masculine race will be the result, and will appear so different from the first, as hardly to be allowed to have one common origin, and which consequently will be regarded as really distinct and separate species.