Passing from the supposed common progenitor to the resemblances between the brain of the higher apes and the brain of man, we come to the question whether these resemblances show that man was descended from any of the Simian stock through intermediate animals by gradual transformation. Here the case is in one respect different; for the animals that are to be compared are known, and their respective brains have been subjected to close anatomical scrutiny. This part of the process of evolution begins from one true species, the ape, and ends in another true species, the man. We are unable to trace the man and the ape to a common progenitor race; but we find the ape possessed of a brain which strongly resembles man's. I have searched diligently in the writings of naturalists for a sound reason which ought rationally to exclude the hypothesis that the brain of the ape was formed upon the same ideal plan as the brain of man, each animal being a distinct species and separately created. Anatomical comparison of the two brains shows that, whether they were separately planned upon the same general model, or the one was derived from the other by a process of gradual transformation through successive intermediate animals, the resemblances are consistent with either hypothesis. We are remitted, therefore, to an inquiry for the evidence which will establish the existence of a race or races of animals through whom there descended to man the peculiar structure of brain found in one of the classes of apes--namely, the Catarrhine or Old World monkeys. If such intermediate races could be found, their existence at any period anterior to the period of man's appearance on earth would have some tendency to show that man was descended from one of the families of apes, and this tendency would become stronger in proportion to the number of successive links in the family chain that could be made out. But not one of these links is known to have existed. There is an assumption that man, "from a genealogical point of view, belongs to the Catarrhine or Old World stock" of monkeys; and this assumption is claimed to be supported by the fact that the character of his brain is fundamentally the same as theirs.