Memory, then, pertains to all that class of psychical states which are in process of being organised. It continues so long as the organising of them continues; and disappears when the organisation of them is complete. In the advance of the correspondence, each more complex class of phenomena which the organism acquires the power of recognising is responded to at first irregularly and uncertainly; and there is then a weak remembrance of the relations. By multiplication of experiences this remembrance becomes stronger, and the response more certain. By further multiplication of experiences the internal relations are at last automatically organised in correspondence with the external ones; and so conscious memory passes into unconscious or organic memory. At the same time, a new and still more complex order of experiences is thus rendered appreciable; the relations they present occupy the memory in place of the simpler one; they become gradually organised; and, like the previous ones, are succeeded by others more complex still (p. 563). Just as we saw that the establishment of those compound reflex actions which we call instincts is comprehensible on the principle that inner relations are, by perpetual repetition, organised into correspondence with outer relations; so the establishment of those consolidated, those indissoluble, those instinctive mental relations constituting our ideas of Space and Time, is comprehensible on the same principle (p. 579). In a book published a few weeks before Mr. Spencer’s letter appeared {29a} I had said that though Mr. Spencer at times closely approached Professor Hering and “Life and Habit,” he had nevertheless nowhere shown that he considered memory and heredity to be parts of the same story and parcel of one another. In his letter to the _Athenæum_, indeed, he does not profess to have upheld this view, except “by implications;” nor yet, though in the course of the six or seven years that had elapsed since “Life and Habit” was published I had brought out more than one book to support my earlier one, had he said anything during those years to lead me to suppose that I was trespassing upon ground already taken by himself. Nor, again, had he said anything which enabled me to appeal to his authority—which I should have been only too glad to do; at last, however, he wrote, as I have said, to the _Athenæum_ a letter which, indeed, made no express claim, and nowhere mentioned myself, but “the meanings and implications” from which were this time as clear as could be desired, and amount to an order to Professor Hering and myself to stand aside.