Introduction to Professor Hering's lecture.
After I had finished "Evolution, Old and New," I wrote some articles for the Examiner,  in which I carried out the idea put forward in "Life and Habit," that we are one person with our ancestors. It follows from this, that all living animals and vegetables, being--as appears likely if the theory of evolution is accepted--descended from a common ancestor, are in reality one person, and unite to form a body corporate, of whose existence, however, they are unconscious. There is an obvious analogy between this and the manner in which the component cells of our bodies unite to form our single individuality, of which it is not likely they have a conception, and with which they have probably only the same partial and imperfect sympathy as we, the body corporate, have with them. In the articles above alluded to I separated the organic from the inorganic, and when I came to rewrite them, I found that this could not be done, and that I must reconstruct what I had written. I was at work on this--to which I hope to return shortly--when Dr. Krause's' "Erasmus Darwin," with its preliminary notice by Mr. Charles Darwin, came out, and having been compelled, as I have shown above, by Dr. Krause's work to look a little into the German language, the opportunity seemed favourable for going on with it and becoming acquainted with Professor Hering's lecture. I therefore began to translate his lecture at once, with the kind assistance of friends whose patience seemed inexhaustible, and found myself well rewarded for my trouble.
Professor Hering and I, to use a metaphor of his own, are as men who have observed the action of living beings upon the stage of the world, he from the point of view at once of a spectator and of one who has free access to much of what goes on behind the scenes, I from that of a spectator only, with none but the vaguest notion of the actual manner in which the stage machinery is worked. If two men so placed, after years of reflection, arrive independently of one another at an identical conclusion as regards the manner in which this machinery must have been invented and perfected, it is natural that each should take a deep interest in the arguments of the other, and be anxious to put them forward with the utmost possible prominence. It seems to me that the theory which Professor Hering and I are supporting in common, is one the importance of which is hardly inferior to that of the theory of evolution itself--for it puts the backbone, as it were, into the theory of evolution. I shall therefore make no apology for laying my translation of Professor Hering's work before my reader.
Concerning the identity of the main idea put forward in "Life and Habit" with that of Professor Hering's lecture, there can hardly, I think, be two opinions. We both of us maintain that we grow our limbs as we do, and possess the instincts we possess, because we remember having grown our limbs in this way, and having had these instincts in past generations when we were in the persons of our forefathers--each individual life adding a small (but so small, in any one lifetime, as to be hardly appreciable) amount of new experience to the general store of memory; that we have thus got into certain habits which we can now rarely break; and that we do much of what we do unconsciously on the same principle as that (whatever it is) on which we do all other habitual actions, with the greater ease and unconsciousness the more often we repeat them. Not only is the main idea the same, but I was surprised to find how often Professor Hering and I had taken the same illustrations with which to point our meaning.
Nevertheless, we have each of us left undealt with some points which the other has treated of. Professor Hering, for example, goes into the question of what memory is, and this I did not venture to do. I confined myself to saying that whatever memory was, heredity was also. Professor Hering adds that memory is due to vibrations of the molecules of the nerve fibres, which under certain circumstances recur, and bring about a corresponding recurrence of visible action.
This approaches closely to the theory concerning the physics of memory which has been most generally adopted since the time of Bonnet, who wrote as follows:-
"The soul never has a new sensation but by the inter position of the senses. This sensation has been originally attached to the motion of certain fibres. Its reproduction or recollection by the senses will then be likewise connected with these same fibres." . . . [54a]
"It appeared to me that since this memory is connected with the body, it must depend upon some change which must happen to the primitive state of the sensible fibres by the action of objects. I have, therefore, admitted as probable that the state of the fibres on which an object has acted is not precisely the same after this action as it was before I have conjectured that the sensible fibres experience more or less durable modifications, which constitute the physics of memory and recollection." [54b]
Professor Hering comes near to endorsing this view, and uses it for the purpose of explaining personal identity. This, at least, is what he does in fact, though perhaps hardly in words. I did not say more upon the essence of personality than that it was inseparable from the idea that the various phases of our existence should have flowed one out of the other, "in what we see as a continuous, though it may be at times a very troubled, stream"  but I maintained that the identity between two successive generations was of essentially the same kind as that existing between an infant and an octogenarian. I thus left personal identity unexplained, though insisting that it was the key to two apparently distinct sets of phenomena, the one of which had been hitherto considered incompatible with our ideas concerning it. Professor Hering insists on this too, but he gives us farther insight into what personal identity is, and explains how it is that the phenomena of heredity are phenomena also of personal identity.
He implies, though in the short space at his command he has hardly said so in express terms, that personal identity as we commonly think of it--that is to say, as confined to the single life of the individual--consists in the uninterruptedness of a sufficient number of vibrations, which have been communicated from molecule to molecule of the nerve fibres, and which go on communicating each one of them its own peculiar characteristic elements to the new matter which we introduce into the body by way of nutrition. These vibrations may be so gentle as to be imperceptible for years together; but they are there, and may become perceived if they receive accession through the running into them of a wave going the same way as themselves, which wave has been set up in the ether by exterior objects and has been communicated to the organs of sense.
As these pages are on the point of leaving my hands, I see the following remarkable passage in Mind for the current month, and introduce it parenthetically here:-
"I followed the sluggish current of hyaline material issuing from globules of most primitive living substance. Persistently it followed its way into space, conquering, at first, the manifold resistances opposed to it by its watery medium. Gradually, however, its energies became exhausted, till at last, completely overwhelmed, it stopped, an immovable projection stagnated to death-like rigidity. Thus for hours, perhaps, it remained stationary, one of many such rays of some of the many kinds of protoplasmic stars. By degrees, then, or perhaps quite suddenly, HELP WOULD COME TO IT FROM FOREIGN BUT CONGRUOUS SOURCES. IT WOULD SEEM TO COMBINE WITH OUTSIDE COMPLEMENTAL MATTER drifted to it at random. Slowly it would regain thereby its vital mobility. Shrinking at first, but gradually completely restored and reincorporated into the onward tide of life, it was ready to take part again in the progressive flow of a new ray." 
To return to the end of the last paragraph but one. If this is so-- but I should warn the reader that Professor Hering is not responsible for this suggestion, though it seems to follow so naturally from what he has said that I imagine he intended the inference to be drawn,--if this is so, assimilation is nothing else than the communication of its own rhythms from the assimilating to the assimilated substance, to the effacement of the vibrations or rhythms heretofore existing in this last; and suitability for food will depend upon whether the rhythms of the substance eaten are such as to flow harmoniously into and chime in with those of the body which has eaten it, or whether they will refuse to act in concert with the new rhythms with which they have become associated, and will persist obstinately in pursuing their own course. In this case they will either be turned out of the body at once, or will disconcert its arrangements, with perhaps fatal consequences. This comes round to the conclusion I arrived at in "Life and Habit," that assimilation was nothing but the imbuing of one thing with the memories of another. (See "Life and Habit," pp. 136, 137, 140, &c.)
It will be noted that, as I resolved the phenomena of heredity into phenomena of personal identity, and left the matter there, so Professor Hering resolves the phenomena of personal identity into the phenomena of a living mechanism whose equilibrium is disturbed by vibrations of a certain character--and leaves it there. We now want to understand more about the vibrations.
But if, according to Professor Hering, the personal identity of the single life consists in the uninterruptedness of vibrations, so also do the phenomena of heredity. For not only may vibrations of a certain violence or character be persistent unperceived for many years in a living body, and communicate themselves to the matter it has assimilated, but they may, and will, under certain circumstances, extend to the particle which is about to leave the parent body as the germ of its future offspring. In this minute piece of matter there must, if Professor Hering is right, be an infinity of rhythmic undulations incessantly vibrating with more or less activity, and ready to be set in more active agitation at a moment's warning, under due accession of vibration from exterior objects. On the occurrence of such stimulus, that is to say, when a vibration of a suitable rhythm from without concurs with one within the body so as to augment it, the agitation may gather such strength that the touch, as it were, is given to a house of cards, and the whole comes toppling over. This toppling over is what we call action; and when it is the result of the disturbance of certain usual arrangements in certain usual ways, we call it the habitual development and instinctive characteristics of the race. In either case, then, whether we consider the continued identity of the individual in what we call his single life, or those features in his offspring which we refer to heredity, the same explanation of the phenomena is applicable. It follows from this as a matter of course, that the continuation of life or personal identity in the individual and the race are fundamentally of the same kind, or, in other words, that there is a veritable prolongation of identity or oneness of personality between parents and offspring. Professor Hering reaches his conclusion by physical methods, while I reached mine, as I am told, by metaphysical. I never yet could understand what "metaphysics" and "metaphysical" mean; but I should have said I reached it by the exercise of a little common sense while regarding certain facts which are open to every one. There is, however, so far as I can see, no difference in the conclusion come to.
The view which connects memory with vibrations may tend to throw light upon that difficult question, the manner in which neuter bees acquire structures and instincts, not one of which was possessed by any of their direct ancestors. Those who have read "Life and Habit" may remember, I suggested that the food prepared in the stomachs of the nurse-bees, with which the neuter working bees are fed, might thus acquire a quasi-seminal character, and be made a means of communicating the instincts and structures in question.  If assimilation be regarded as the receiving by one substance of the rhythms or undulations from another, the explanation just referred to receives an accession of probability.
If it is objected that Professor Hering's theory as to continuity of vibrations being the key to memory and heredity involves the action of more wheels within wheels than our imagination can come near to comprehending, and also that it supposes this complexity of action as going on within a compass which no unaided eye can detect by reason of its littleness, so that we are carried into a fairy land with which sober people should have nothing to do, it may be answered that the case of light affords us an example of our being truly aware of a multitude of minute actions, the hundred million millionth part of which we should have declared to be beyond our ken, could we not incontestably prove that we notice and count them all with a very sufficient and creditable accuracy.
"Who would not," [59a] says Sir John Herschel, "ask for demonstration when told that a gnat's wing, in its ordinary flight, beats many hundred times in a second? or that there exist animated and regularly organised beings many thousands of whose bodies laid close together would not extend to an inch? But what are these to the astonishing truths which modern optical inquiries have disclosed, which teach us that every point of a medium through which a ray of light passes is affected with a succession of periodical movements, recurring regularly at equal intervals, no less than five hundred millions of millions of times in a second; that it is by such movements communicated to the nerves of our eyes that we see; nay, more, that it is the DIFFERENCE in the frequency of their recurrence which affects us with the sense of the diversity of colour; that, for instance, in acquiring the sensation of redness, our eyes are affected four hundred and eighty-two millions of millions of times; of yellowness, five hundred and forty-two millions of millions of times; and of violet, seven hundred and seven millions of millions of times per second? [59b] Do not such things sound more like the ravings of madmen than the sober conclusions of people in their waking senses? They are, nevertheless, conclusions to which any one may most certainly arrive who will only be at the pains of examining the chain of reasoning by which they have been obtained."
A man counting as hard as he can repeat numbers one after another, and never counting more than a hundred, so that he shall have no long words to repeat, may perhaps count ten thousand, or a hundred a hundred times over, in an hour. At this rate, counting night and day, and allowing no time for rest or refreshment, he would count one million in four days and four hours, or say four days only. To count a million a million times over, he would require four million days, or roughly ten thousand years; for five hundred millions of millions, he must have the utterly unrealisable period of five million years. Yet he actually goes through this stupendous piece of reckoning unconsciously hour after hour, day after day, it may be for eighty years, OFTEN IN EACH SECOND of daylight; and how much more by artificial or subdued light I do not know. He knows whether his eye is being struck five hundred millions of millions of times, or only four hundred and eighty-two millions of millions of times. He thus shows that he estimates or counts each set of vibrations, and registers them according to his results. If a man writes upon the back of a British Museum blotting-pad of the common nonpareil pattern, on which there are some thousands of small spaces each differing in colour from that which is immediately next to it, his eye will, nevertheless, without an effort assign its true colour to each one of these spaces. This implies that he is all the time counting and taking tally of the difference in the numbers of the vibrations from each one of the small spaces in question. Yet the mind that is capable of such stupendous computations as these so long as it knows nothing about them, makes no little fuss about the conscious adding together of such almost inconceivably minute numbers as, we will say, 2730169 and 5790135--or, if these be considered too large, as 27 and 19. Let the reader remember that he cannot by any effort bring before his mind the units, not in ones, BUT IN MILLIONS OF MILLIONS of the processes which his visual organs are undergoing second after second from dawn till dark, and then let him demur if he will to the possibility of the existence in a germ, of currents and undercurrents, and rhythms and counter rhythms, also by the million of millions--each one of which, on being overtaken by the rhythm from without that chimes in with and stimulates it, may be the beginning of that unsettlement of equilibrium which results in the crash of action, unless it is timely counteracted.
If another objector maintains that the vibrations within the germ as above supposed must be continually crossing and interfering with one another in such a manner as to destroy the continuity of any one series, it may be replied that the vibrations of the light proceeding from the objects that surround us traverse one another by the millions of millions every second yet in no way interfere with one another. Nevertheless, it must be admitted that the difficulties of the theory towards which I suppose Professor Hering to incline are like those of all other theories on the same subject--almost inconceivably great.
In "Life and Habit" I did not touch upon these vibrations, knowing nothing about them. Here, then, is one important point of difference, not between the conclusions arrived at, but between the aim and scope of the work that Professor Hering and I severally attempted. Another difference consists in the points at which we have left off. Professor Hering, having established his main thesis, is content. I, on the other hand, went on to maintain that if vigour was due to memory, want of vigour was due to want of memory. Thus I was led to connect memory with the phenomena of hybridism and of old age; to show that the sterility of certain animals under domestication is only a phase of, and of a piece with, the very common sterility of hybrids--phenomena which at first sight have no connection either with each other or with memory, but the connection between which will never be lost sight of by those who have once laid hold of it. I also pointed out how exactly the phenomena of development agreed with those of the abeyance and recurrence of memory, and the rationale of the fact that puberty in so many animals and plants comes about the end of development. The principle underlying longevity follows as a matter of course. I have no idea how far Professor Hering would agree with me in the position I have taken in respect of these phenomena, but there is nothing in the above at variance with his lecture.
Another matter on which Professor Hering has not touched is the bearing of his theory on that view of evolution which is now commonly accepted. It is plain he accepts evolution, but it does not appear that he sees how fatal his theory is to any view of evolution except a teleological one--the purpose residing within the animal and not without it. There is, however, nothing in his lecture to indicate that he does not see this.
It should be remembered that the question whether memory is due to the persistence within the body of certain vibrations, which have been already set up within the bodies of its ancestors, is true or no, will not affect the position I took up in "Life and Habit." In that book I have maintained nothing more than that whatever memory is heredity is also. I am not committed to the vibration theory of memory, though inclined to accept it on a prima facie view. All I am committed to is, that if memory is due to persistence of vibrations, so is heredity; and if memory is not so due, then no more is heredity.
Finally, I may say that Professor Hering's lecture, the passage quoted from Dr. Erasmus Darwin on p. 26 of this volume, and a few hints in the extracts from Mr. Patrick Mathew which I have quoted in "Evolution, Old and New," are all that I yet know of in other writers as pointing to the conclusion that the phenomena of heredity are phenomena also of memory.
 Since published as "God the Known and God the Unknown." Fifield, 1s. 6d. net. 1909.
[54a] "Contemplation of Nature," Engl. trans., Lond. 1776. Preface, p. xxxvi.
[54b] Ibid., p. xxxviii.
 Life and Habit, p. 97.
 "The Unity of the Organic Individual," by Edward Montgomery, Mind, October 1880, p. 466.
 Life and Habit, p. 237.
[59a] Discourse on the Study of Natural Philosophy. Lardner's Cab. Cyclo., vol. xcix. p. 24.
[59b] Young's Lectures on Natural Philosophy, ii. 627. See also Phil. Trans., 1801-2.