direct cause, than to a multitude of secondary causes. There is a world-wide difference between the dog-_ego_ and the man-_ego;_ but the physical differences are not by any means the greatest. The bioplastic spinners and weavers work as obediently for the one master-_ego_ as the other. They never stop to inquire how far they shall differentiate this vital tissue or that, or in what direction even they shall work. Not a thread is spun nor a shuttle thrown that is not directed by the one head-webster of vital tissue. These obedient bioplasts determine nothing, direct nothing. Each works in his own cell as obediently as a galley-slave. All specific modifications, all determinate movements, all molecular arrangements, all multiplications of bioplastic force, are the work of the one vital webster, or principle of life, within--that which shapes all, directs all, determines all. And this is true from the first or embryological inception of the dog-unit or "germ," until the real occupant of the dog-tenement dismisses his bioplastic weavers, and lies down to die. And so of all vital units. Each determines its own structural form, and unchangeably retains it to the end, even to the slightest impression of a scar inflicted years and years before. The occupant of this dog-mansion has dismissed one set of bioplastic weavers after another; has thrown aside this spun tissue and that warp and woof of woven texture, time and time again, so that the dog of to-day is not the same _physical_ dog of a year ago; and yet he has the same affection for his master, carries with him the same scar received twenty years before in the chase, gives the same glad bark of welcome as his owner nears home, exhibits the same characteristic wag in his tail, and, lying down to sleep, dreams of the once happy chase in which he is no longer able to engage. This continuous presence of the same dog, through all these twenty years of physical change--the old dog reappearing in the new, a dozen times over--is what we mean by the constantly differentiating yet undifferentiated "dog-unit."