Can we apply this mode of reasoning to the evolution of distinct types of animals out of antecedent and different types? The very nature of the descent or derivation that is to be satisfactorily established requires a connection of lives with lives, just as such a connection is required in making out the pedigree of an individual animal. We must construct a pedigree for the different classes or types of animals through which, by direct or collateral evidence, we can connect the different organisms together, so as to warrant the belief that by the ordinary process of generation these animals of widely different organizations have been successfully developed out of each other, life from life, organisms from organisms. The hypothesis is, that from a single cell all the various races and types of animals have in process of time been gradually formed out of each other, through an ascending scale, until we reach the human race, whose race pedigree consists of a series of imperceptible formations, back to the single cell from which the whole series proceeded. This, we must remember, is not a case of the evolving production of different forms of inanimate matter, but it is the case of the evolving production of different forms of animal life out of other preceding and different forms, by the process of animal generation. Of direct evidence of this evolution of species, it can not be said that we have any which will make it a parallel case with the direct evidence of the descent of an individual from parents and other ancestors. We have different animal organisms that are marked by distinctions which compel us to regard them as separate species, and there is no known instance in which we can directly trace a production of one of these distinct species out of another or others by finding a connection of lives with lives. Even in the vegetable kingdom, with all the crosses for which Nature has made such wonderful and various provision, we do not find such occurrences as the production of an oak out of the seed of an apple, or the production of an orange-tree out of an acorn. We do not gather grapes of thorns or figs of thistles. There are barriers set to miscegenation even in the vegetable world, and we have no direct evidence that at any period in the geological history of the earth these barriers have been crossed, and very little indirect evidence to warrant us in believing that they ever have been or ever will be. In the animal kingdom such barriers are extremely prominent and certain. We not only have no direct evidence that any one species of animal was at any period of the earth's history or in any length of time gradually evolved out of another distinct species, but we know that the union of the sexes and the production of new individuals can not take place out of certain limits; that, while Nature will permit of the crossing of different breeds of the same animal, and so will admit of very limited variations of structure, she will not admit of