They show that there are animals known as apes and animals known as men, whose brains are found to be fundamentally constructed upon the same general plan, with strong resemblances throughout the different parts of the organ; and the first question is, Do these resemblances show that the two animals came from a common stock? Upon the theory that man has resulted from the gradual modifications of the same form as that from which the apes have sprung, the resemblances in the structure of their respective brains are claimed as having a tendency to show that there was an animal which preceded both of them, and which was their common ancestor, in the same sense in which an individual progenitor was the common ancestor of two other individuals, whether one of these two individuals was or was not descended from the other in a direct line. On the other hand, upon the hypothesis of the special creation of the ape as one animal, and the special creation of man as another animal, there was no common stock from which the two animals have been derived, and the resemblances of their brains point to the adoption of a general plan of construction for that organ, or its construction upon the same model, and the adaptation of that model to the other parts of the structure, and the purposes of the existence of each of the two animals. Without again repeating the argument which shows that the latter hypothesis is perfectly consistent with the professed conception of the infinite power, I will now inquire whether, on the former hypothesis, we have anything to which we can apply the evidence of resemblance as a collateral aid in reaching the conclusion that these two animals were derived from a common progenitor, or from some antecedent animal whose brain and other parts of the structure became modified into theirs by numerous intermediate gradations.