I made a note, half mechanically, of a page in a botanical work from which later on I was going to make an extract. Something was in my mind in henid form. What I thought, how I thought it, what was then knocking at the door of my consciousness, I could not remember a minute afterwards, in spite of the hardest effort. I take this case as a typical example of the henid. The more deeply impressed, the more detailed a complex perception may be the more easily does it reproduce itself. Clearness of the consciousness is the preliminary condition for remembering, and the memory of the mental stimulation is proportional to the intensity of the consciousness. “I shall not forget that”; “I shall remember that all my life”; “That will never escape my memory again.” Such phrases men use when things have made a deep impression on them, of moments in which they have gained wisdom or have become richer by an important experience. As the power of being reproduced is directly proportionate to the organisation of a mental impression, it is clear that there can be no recollection of an absolute henid. As the mental endowment of a man varies with the organisation of his accumulated experiences, the better endowed he is, the more readily will he be able to remember his whole past, everything that he has ever thought or heard, seen or done, perceived or felt, the more completely in fact will he be able to reproduce his whole life. Universal remembrance of all its experiences, therefore, is the sure, most general, and most easily proved mark of a genius. If a common theory, especially popular with the philosophers of the coffee-house, be true, that productive men (because they are always covering new ground) have no memory, it is often because they are productive only from being on new ground.