fire-mist and for long afterwards they were not in being. None the less when they did actually come into being, under conditions of which we are at present ignorant--though not so ignorant as we were--they were dependent upon, and, for our interpretation, they logically imply, the physico-chemical relations which are also present. In any given case they further imply, through heredity-relatedness, the evolutionary history of the organism in which they obtain. This so-called historical element in biology no doubt involves a characteristic vital relationship. But, I take it, the physico-chemical constitution of any inorganic compound, and of any molecule therein, has also its history--has relationship to past occurrences within its type, which have helped to make it what it is. Still, in the organism the relation to past happenings has a quite distinctive form which we deal with in terms of heredity. See, then, how we stand so far. The internal physiological process implies a long chain of heredity-relationships through which the organism is prepared for its occurrence. It also implies a physico-chemical basis, an underlying[70] physico-chemical process. And this implies as a condition of its occurrence, the external event, the passage of the billiard-ball across the table. In a broad sense we may say that the inner process knows the external event which is a condition of its occurrence. But we have not yet reached cognition of the psychological type. Before passing on to indicate, in tentative outline, the nature of this higher mode of relatedness, I pause to note two points. The first is that knowing in that extended sense which I have borrowed,[71] is essentially selective in its nature. The physiological process, in the case I have taken, knows only that external event which is directly before the eyes and which is serially correlated with changes in the retinal images through the stimulation of specialized receptors. Of other external events it has no such knowledge. Compare this with the gravitative knowledge--if a yet wider extension of the meaning of the word be permitted--which the earth has of the sun and all the other members of the solar system--nay more, in degrees perhaps infinitesimal, of all other material bodies in the universe. The motion of the earth in its orbit implies the whole of this vast field of gravitative relatedness. The existing orbital motion at any moment implies, too, the preceding motion which it has, in a sense, inherited from the past. Abolish the rest of the universe at this moment and the earth's motion would cease to be orbital. In virtue of its 'inheritance from the past', it would continue at uniform velocity in one direction. The continuous change of direction and velocity we observe, is a response which implies gravitative knowledge. In a sense, then, the whole solar system is known by the earth as it swings in its orbit.