Obviously the memory of a habit or experience will not commonly be transmitted to offspring in that perfection which is called “instinct,” till the habit or experience has been repeated in several generations with more or less uniformity; for otherwise the impression made will not be strong enough to endure through the busy and difficult task of reproduction. This of course involves that the habit shall have attained, as it were equilibrium with the creature’s sense of its own needs, so that it shall have long seemed the best course possible, leaving upon the whole and under ordinary circumstances little further to be desired, and hence that it should have been little varied during many generations. We should expect that it would be transmitted in a more or less partial, varying, imperfect, and intelligent condition before equilibrium had been attained; it would, however, continually tend towards equilibrium, for reasons which will appear more fully later on. When this stage has been reached, as regards any habit, the creature will cease trying to improve; on which the repetition of the habit will become stable, and hence become capable of more unerring transmission—but at the same time improvement will cease; the habit will become fixed, and be perhaps transmitted at an earlier and earlier age, till it has reached that date of manifestation which shall be found most agreeable to the other habits of the creature. It will also be manifested, as a matter of course, without further consciousness or reflection, for people cannot be always opening up settled questions; if they thought a matter over yesterday they cannot think it all over again to-day, but will adopt for better or worse the conclusion then reached; and this, too, even in spite sometimes of considerable misgiving, that if they were to think still further they could find a still better course. It is not, therefore, to be expected that “instinct” should show signs of that hesitating and tentative action which results from knowledge that is still so imperfect as to be actively self-conscious; nor yet that it should grow or vary, unless under such changed conditions as shall baffle memory, and present the alternative of either invention—that is to say, variation—or death. But every instinct must have poised through the laboriously intelligent stages through which human civilisations _and mechanical inventions_ are now passing; and he who would study the origin of an instinct with its development, partial transmission, further growth, further transmission, approach to more unreflecting stability, and finally, its perfection as an unerring and unerringly transmitted instinct, must look to laws, customs, _and machinery_ as his best instructors. Customs and machines are instincts _and organs_ now in process of development; they will assuredly one day reach the unconscious state of equilibrium which we observe in the structures and instincts of bees and ants, and an approach