It may be said all this is habit. But what is habit? Is it any explanation to say a creature performs a given action by habit? or is it not rather playing with a word which expresses a phenomenon without explaining it? Directly we bring memory into the field we get a real explanation. A habit is acquired by repetition, and could not arise if the preceding experience were forgotten. Life is largely made up of repetition, which involves the formation of habits; and, indeed, everyone's experience (habit again) shows that life only runs smoothly when certain necessary habits have been acquired so perfectly as to be performed without effort. A being at maturity is a great storehouse of acquired habits; and of these many are so perfectly acquired, _i.e._, have been performed so frequently, that the possessor is quite unconscious of possessing them. Habit tends to become automatic; indeed, a habit can hardly be said to be formed until it is automatic. But habits are the result of experience and repetition, that is, have arisen in the first instance by some reasoning process; and reasoning implies consciousness. Nevertheless, the action once thought out, or reasoned upon, requires less conscious effort on a second occasion, and still less on a third, and so on, until the mere occurrence of given conditions is sufficient to ensure immediate response without conscious effort, and the action is performed mechanically or automatically: it is now a true habit. Habit, then, commences in consciousness and ends in unconsciousness. To say, therefore, when we see an action performed without conscious thought, that consciousness has never had part in its production, is as illogical as to say that because we read automatically we can never have learned to read. The thorough appreciation of this principle is absolutely essential to the argument of this work; for to inherited memory we attribute not only the formation of habits and instincts, but also the modification of organs, which leads to the formation of new species. In a word, it is to memory we attribute the possibility of evolution, and by it the struggle for existence is enabled to re-act upon the forms of life, and produce the harmony we see in the organic world. Our own investigations had led us very far in this direction; but we failed to grasp the entire truth until Mr. S. Butler's remarkable work, "Life and Habit," came to our notice. This valuable contribution to evolution smoothed away the whole of the difficulties we had experienced, and enabled us to propound the views here set forth with greater clearness than had been anticipated.