What, then, does the establishment of a like system of procreation and gestation imply, upon the supposition of the distinct creation of species? It implies a certain parallel embryonic development, from the germ to the fœtus and from the fœtus to the new-born infant, throughout a large group of different animals; and this parallelism would in certain stages of the embryonic growth display identity or close similarity of form and structure. But as in each species of animal the distinct creation would necessarily imply a distinct destiny, the parallelism of embryonic form and structure would cease at the point of development at which the characteristic structure of the species would begin to unfold itself. The general system of procreation and gestation common to a whole class of different animals, and the ordained diversity of species, would present the same phenomena of resemblances and differences in the embryonic development that are supposed to be explicable only by the hypothesis of a descent of all the species from a common ancestral stock through the process of evolution. Notwithstanding the mystery and obscurity in which the process of animal procreation is involved--a mystery and obscurity which will perhaps never be fully solved--we can see enough to warrant some definite conclusions. One of these conclusions is that, in the formation of the germ which becomes developed into the fœtus, the male and female parent each contributes some cellular substance to the compound which constitutes that germ. We may safely infer this, because the individual animal becomes a union of characteristics belonging to both the parents, although the traits that are peculiar to one of the parents may be more or less marked in their different offspring, so that in one of the descendants the paternal and in another the maternal traits will predominate. But in every descendant from the same pair there is more or less of the peculiarities of each parent plainly discernible. The inference, therefore, may be safely drawn that the male and the female parent each contributes to the formation of the ante-fœtal germ some cellular substance, in which resides the typical characteristic of animal organism which each parent possesses. The compound germ that is thus formed is endowed with the mysterious principle of animal life which admits of growth and development; and whether after its formation the female parent bestows most or bestows least upon the product, that product consists of a union of cellular substances contributed by both the male and the female parent in the sexual act of procreation. This compound resultant germ, in the earliest stage of its formation, like the separate cells of which it is a union, exhibits no visible difference when we compare the ante-fœtal germ of one animal with that of a different animal. Perhaps we shall never be able to detect either chemical or mechanical differences