covered relatively little; their works were mostly speculations and vague hypotheses. As Aristotle himself says, "I found no basis prepared; no models to copy … Mine is the first step, and therefore a small one, though worked out with much thought and hard labor. It must be looked at as a first step and judged with indulgence. You, my readers, or hearers of my lectures, if you think I have done as much as can be fairly required for an initiatory start, as compared with more advanced departments of theory, will acknowledge what I have achieved and pardon what I have left for others to accomplish."
In his two books, "Physics" and "Natural History of Animals" are set forth Aristotle's views on nature, and his remarkably accurate observations of both plants and animals. He distinguished about five hundred species of mammals, birds, and fishes, besides showing an extensive knowledge of corals and their allies, sponges, squids, and other marine animals. He understood the adaptation of animals and their parts to the needs placed upon them, and was familiar with the commoner principles of heredity. He considered life to be a function of the animal or plant exhibiting it, and not a separate entity, given out by some divine power, or mysterious force. Aristotle devised a hereditary chain, extending from the simplest animals of which he had knowledge to the highest, man. This chain was a very direct affair, not at all resembling the modern "evolutionary tree" in its various ramifications and irregulari-
