Thinkers of all times have asked themselves the question whence does this world come on which we live. Curious to know whether the universe was self-made, or was the work of a great primal ancestor, or personal Creator; philosophers who considered the matter in its entirety have left us two hypotheses. “According to one, chaos reigned at the beginning, or in other words, the possibility of everything; and from the midst of this chaos certain realities were evolved,”[1] from an inherent aptitude for development; this aptitude has been named in many ways, such as “natural selection,” “survival of the fittest.” The Greek sages were already acquainted with the thought implied in these terms. Empedocles said that the fittest would always preponderate, since conservation is an integral part of their nature; whilst what is unfit, or not in accord with the surroundings, must disappear. But the partisans of this theory find themselves confronted by a serious difficulty: if a blind force has produced the universe, whence comes the order which reigns in nature? It is freely acknowledged, even by those with small powers of observation, that the inhabitants of the terrestrial globe are divided into animal and vegetable, which are again subdivided into distinct classes, separated by distinct lines of demarcation. If we admitted that the vegetable and animal kingdoms were not at first so entirely separated as they are at present, there would always remain a question awaiting reply: How is it to be accounted for, that two families issuing from the same source, become so separated, and have remained distinct ever since?