In what way, then, are these substitutions unaccountable as results of design, and why are they any more congruous with the supposition that the mammalian type arose out of the lower vertebrate type? In the first place, it is necessary to have a distinct conception of what is meant by design. In the present case, it means that for a certain large group of animals there was established a system of reproduction by the sexual union of male and female, each contributing a cellular substance peculiar to itself, in the formation of a compound cellular substance in which the separate substances are united, and which is to be developed into the fœtus by a law of growth; and as a further design there is wrapped up in the compound germ of each distinct species of animal a typical plan of ultimate form and structure. This typical plan can not be detected in the germ itself, as it is too subtile and obscure even for the microscope; but we have every reason to believe that it is there in all its distinctness of original purpose, because at a later stage of the embryonic development we find a distinct species of animal is the result. This is a conclusion that must be adopted by the evolutionist, as well as by the believer in special creations, because it has nothing to do with the question of how distinct species came to exist. Whether they were designedly and separately created, or were evolved out of one another, the reproductive process by which the individuals of the same species are brought into being alike involves the conclusion that, in the ante-fœtal germ of that species, there is somehow involved, in a form so minute that it can not be seen, the type of animal which is to belong to that species, and to no other. Here, then, we have the grand and compound design which is to obtain throughout a whole group of different animals; namely, that they shall multiply in the production of individuals of their own types, by a sexual union, in which the male and the female each contributes a cellular substance of its own to the formation of a compound germ, and in that germ there is made to reside the typical form and structure of a distinct organism, so minute that we can not see it, but which we must conclude from the result has been put there to be developed by a law of growth ordained for the accomplishment of a certain distinct order of beings. But the very obscurity of this type, in the earliest stage of embryonic development, leads to the conclusion that while it will never be lost, so long as its life is preserved, it will unfold itself in ways that will be equally beyond our ken, until the point is reached where it is no longer obscured, but where it is revealed in all its distinctness of outline and its peculiarity of structure. What is certain and invariable is, that the type peculiar to the species is at some time in the growth of the individual animal perfectly developed. But in the