At the close of my article in last month’s number of the Universal Review, I said I would in this month’s issue show why the opponents of Charles-Darwinism believe the effects of habits acquired during the lifetime of a parent to produce an effect on their subsequent offspring, in spite of the fact that we can rarely find the effect in any one generation, or even in several, sufficiently marked to arrest our attention.

I will now show that offspring can be, and not very infrequently is, affected by occurrences that have produced a deep impression on the parent organism ­the effect produced on the offspring being such as leaves no doubt that it is to be connected with the impression produced on the parent.  Having thus established the general proposition, I will proceed to the more particular one ­that habits, involving use and disuse of special organs, with the modifications of structure thereby engendered, produce also an effect upon offspring, which, though seldom perceptible as regards structure in a single, or even in several generations, is nevertheless capable of being accumulated in successive generations till it amounts to specific and generic difference.  I have found the first point as much as I can treat within the limits of this present article, and will avail myself of the hospitality of the Universal Review next month to deal with the second.

The proposition which I have to defend is one which no one till recently would have questioned, and even now those who look most askance at it do not venture to dispute it unreservedly; they every now and then admit it as conceivable, and even in some cases probable; nevertheless they seek to minimize it, and to make out that there is little or no connection between the great mass of the cells of which the body is composed, and those cells that are alone capable of reproducing the entire organism.  The tendency is to assign to these last a life of their own, apart from, and unconnected with that of the other cells of the body, and to cheapen all evidence that tends to prove any response on their part to the past history of the individual, and hence ultimately of the race.

Professor Weismann is the foremost exponent of those who take this line.  He has naturally been welcomed by English Charles-Darwinians; for if his view can be sustained, then it can be contended that use and disuse produce no transmissible effect, and the ground is cut from under Lamarck’s feet; if, on the other hand, his view is unfounded, the Lamarckian reaction, already strong, will gain still further strength.  The issue, therefore, is important, and is being fiercely contested by those who have invested their all of reputation for discernment in Charles-Darwinian securities.

Professor Weismann’s theory is, that at every new birth a part of the substance which proceeds from parents and which goes to form the new embryo is not used up in forming the new animal, but remains apart to generate the germ-cells ­or perhaps I should say “germ-plasm” ­which the new animal itself will in due course issue.

Contrasting the generally received view with his own, Professor Weismann says that according to the first of these “the organism produces germ-cells afresh again and again, and that it produces them entirely from its own substance.”  While by the second “the germ-cells are no longer looked upon as the product of the parent’s body, at least as far as their essential part ­the specific germ-plasm ­is concerned; they are rather considered as something which is to be placed in contrast with the tout ensemble of the cells which make up the parent’s body, and the germ-cells of succeeding generations stand in a similar relation to one another as a series of generations of unicellular organisms arising by a continued process of cell-division.” On another page he writes: ­

“I believe that heredity depends upon the fact that a small portion of the effective substance of the germ, the germ-plasm, remains unchanged during the development of the ovum into an organism, and that this part of the germ-plasm serves as a foundation from which the germ-cells of the new organism are produced.  There is, therefore, continuity of the germ-plasm from one generation to another.  One might represent the germ-plasm by the metaphor of a long creeping root-stock from which plants arise at intervals, these latter representing the individuals of successive generations.”

Mr. Wallace, who does not appear to have read Professor Weismann’s essays themselves, but whose remarks are, no doubt, ultimately derived from the sequel to the passage just quoted from page 266 of Professor Weismann’s book, contends that the impossibility of the transmission of acquired characters follows as a logical result from Professor Weismann’s theory, inasmuch as the molecular structure of the germ-plasm that will go to form any succeeding generation is already predetermined within the still unformed embryo of its predecessor; “and Weismann,” continues Mr. Wallace, “holds that there are no facts which really prove that acquired characters can be inherited, although their inheritance has, by most writers, been considered so probable as hardly to stand in need of direct proof.”

Professor Weismann, in passages too numerous to quote, shows that he recognizes this necessity, and acknowledges that the non-transmission of acquired characters “forms the foundation of the views” set forth in his book, .

Professor Ray Lankester does not commit himself absolutely to this view, but lends it support by saying (Nature, December 12, 1889):  “It is hardly necessary to say that it has never yet been shown experimentally that anything acquired by one generation is transmitted to the next (putting aside diseases).”

Mr. Romanes, writing in Nature, March 13, 1890, and opposing certain details of Professor Weismann’s theory, so far supports it as to say that “there is the gravest possible doubt lying against the supposition that any really inherited decrease is due to the inherited effects of disuse.”  The “gravest possible doubt” should mean that Mr. Romanes regards it as a moral certainty that disuse has no transmitted effect in reducing an organ, and it should follow that he holds use to have no transmitted effect in its development.  The sequel, however, makes me uncertain how far Mr. Romanes intends this, and I would refer the reader to the article which Mr. Romanes has just published on Weismann in the Contemporary Review for this current month.

The burden of Mr. Thiselton Dyer’s controversy with the Duke of Argyll (see Nature, January 16, 1890, et seq.) was that there was no evidence in support of the transmission of any acquired modification.  The orthodoxy of science, therefore, must be held as giving at any rate a provisional support to Professor Weismann, but all of them, including even Professor Weismann himself, shrink from committing themselves to the opinion that the germ-cells of any organisms remain in all cases unaffected by the events that occur to the other cells of the same organism, and until they do this they have knocked the bottom out of their case.

From among the passages in which Professor Weismann himself shows a desire to hedge I may take the following from page 170 of his book: ­

“I am also far from asserting that the germ-plasm which, as I hold, is transmitted as the basis of heredity from one generation to another, is absolutely unchangeable or totally uninfluenced by forces residing in the organism within which it is transformed into germ-cells.  I am also compelled to admit it as conceivable that organisms may exert a modifying influence upon their germ-cells, and even that such a process is to a certain extent inevitable.  The nutrition and growth of the individual must exercise some influence upon its germ-cells . . . "

Professor Weismann does indeed go on to say that this influence must be extremely slight, but we do not care how slight the changes produced may be, provided they exist and can be transmitted.  On an earlier page he said in regard to variations generally that we should not expect to find them conspicuous; their frequency would be enough, if they could be accumulated.  The same applies here, if stirring events that occur to the somatic cells can produce any effect at all on offspring.  A very small effect, provided it can be repeated and accumulated in successive generations, is all that even the most exacting Lamarckian will ask for.

Having now made the reader acquainted with the position taken by the leading Charles-Darwinian authorities, I will return to Professor Weismann himself, who declares that the transmission of acquired characters “at first sight certainly seems necessary,” and that “it appears rash to attempt to dispense with its aid.”  He continues: ­

“Many phenomena only appear to be intelligible if we assume the hereditary transmission of such acquired characters as the changes which we ascribe to the use or disuse of particular organs, or to the direct influence of climate.  Furthermore, how can we explain instinct as hereditary habit, unless it has gradually arisen by the accumulation, through heredity, of habits which were practised in succeeding generations?”

I may say in passing that Professor Weismann appears to suppose that the view of instinct just given is part of the Charles-Darwinian system, for on page 389 of his book he says “that many observers had followed Darwin in explaining them [instincts] as inherited habits.”  This was not Mr. Darwin’s own view of the matter.  He wrote: ­

“If we suppose any habitual action to become inherited ­and I think it can be shown that this does sometimes happen ­then the resemblance between what originally was a habit and an instinct becomes so close as not to be distinguished. . . .  But it would be the most serious error to suppose that the greater number of instincts have been acquired by habit in one generation, and then transmitted by inheritance to succeeding generations.  It can be clearly shown that the most wonderful instincts with which we are acquainted, namely, those of the hive-bee and of many ants, could not possibly have been thus acquired.” ­[Origin of Species, e, .]

Again we read:  “Domestic instincts are sometimes spoken of as actions which have become inherited solely from long-continued and compulsory habit, but this, I think, is not true.” ­Ibid., .

Again:  “I am surprised that no one has advanced this demonstrative case of neuter insects, against the well-known doctrine of inherited habit, as advanced by Lamarck.” ­[Origin of Species, e, .]

I am not aware that Lamarck advanced the doctrine that instinct is inherited habit, but he may have done so in some work that I have not seen.

It is true, as I have more than once pointed out, that in the later editions of the Origin of Species it is no longer “the most serious” error to refer instincts generally to inherited habit, but it still remains “a serious error,” and this slight relaxation of severity does not warrant Professor Weismann in ascribing to Mr. Darwin an opinion which he emphatically condemned.  His tone, however, is so off-hand, that those who have little acquaintance with the literature of evolution would hardly guess that he is not much better informed on this subject than themselves.

Returning to the inheritance of acquired characters, Professor Weismann says that this has never been proved either by means of direct observation or by experiment.  “It must be admitted,” he writes, “that there are in existence numerous descriptions of cases which tend to prove that such mutilations as the loss of fingers, the scars of wounds, etc., are inherited by the offspring, but in these descriptions the previous history is invariably obscure, and hence the evidence loses all scientific value.”

The experiments of M. Brown-Sequard throw so much light upon the question at issue that I will quote at some length from the summary given by Mr. Darwin in his Variation of Animals and Plants under Domestication. Mr. Darwin writes: ­

“With respect to the inheritance of structures mutilated by injuries or altered by disease, it was until lately difficult to come to any definite conclusion.” [Then follow several cases in which mutilations practised for many generations are not found to be transmitted.] “Notwithstanding,” continues Mr. Darwin, “the above several negative cases, we now possess conclusive evidence that the effects of operations are sometimes inherited.  Dr. Brown-Sequard gives the following summary of his observations on guinea-pigs, and this summary is so important that I will quote the whole: ­

“’1st.  Appearance of epilepsy in animals born of parents having been rendered epileptic by an injury to the spinal cord.

“’2nd.  Appearance of epilepsy also in animals born of parents having been rendered epileptic by the section of the sciatic nerve.

“’3rd.  A change in the shape of the ear in animals born of parents in which such a change was the effect of a division of the cervical sympathetic nerve.

“’4th.  Partial closure of the eyelids in animals born of parents in which that state of the eyelids had been caused either by the section of the cervical sympathetic nerve or the removal of the superior cervical ganglion.

“’5th.  Exophthalmia in animals born of parents in which an injury to the restiform body had produced that protrusion of the eyeball.  This interesting fact I have witnessed a good many times, and I have seen the transmission of the morbid state of the eye continue through four generations.  In these animals modified by heredity, the two eyes generally protruded, although in the parents usually only one showed exophthalmia, the lesion having been made in most cases only on one of the corpora restiformia.

“’6th.  Haematoma and dry gangrene of the ears in animals born of parents in which these ear-alterations had been caused by an injury to the restiform body near the nib of the calamus.

“’7th.  Absence of two toes out of the three of the hind leg, and sometimes of the three, in animals whose parents had eaten up their hind-leg toes which had become anæsthetic from a section of the sciatic nerve alone, or of that nerve and also of the crural.  Sometimes, instead of complete absence of the toes, only a part of one or two or three was missing in the young, although in the parent not only the toes but the whole foot was absent (partly eaten off, partly destroyed by inflammation, ulceration, or gangrene).

“’8th.  Appearance of various morbid states of the skin and hair of the neck and face in animals born of parents having had similar alterations in the same parts, as effects of an injury to the sciatic nerve.’

“It should be especially observed that Brown-Sequard had bred during thirty years many thousand guinea-pigs from animals which had not been operated upon, and not one of these manifested the epileptic tendency.  Nor has he ever seen a guinea-pig born without toes, which was not the offspring of parents which had gnawed off their own toes owing to the sciatic nerve having been divided.  Of this latter fact thirteen instances were carefully recorded, and a greater number were seen; yet Brown-Sequard speaks of such cases as one of the rarer forms of inheritance.  It is a still more interesting fact, ’that the sciatic nerve in the congenitally toeless animal has inherited the power of passing through all the different morbid states which have occurred in one of its parents from the time of the division till after its reunion with the peripheric end.  It is not, therefore, simply the power of performing an action which is inherited, but the power of performing a whole series of actions, in a certain order.’

“In most of the cases of inheritance recorded by Brown-Sequard only one of the two parents had been operated upon and was affected.  He concludes by expressing his belief that ’what is transmitted is the morbid state of the nervous system,’ due to the operation performed on the parents.”

Mr. Darwin proceeds to give other instances of inherited effects of mutilations: ­

“With the horse there seems hardly a doubt that exostoses on the legs, caused by too much travelling on hard roads, are inherited.  Blumenbach records the case of a man who had his little finger on the right hand almost cut off, and which in consequence grew crooked, and his sons had the same finger on the same hand similarly crooked.  A soldier, fifteen years before his marriage, lost his left eye from purulent ophthalmia, and his two sons were microphthalmic on the same side.”

The late Professor Rolleston, whose competence as an observer no one is likely to dispute, gave Mr. Darwin two cases as having fallen under his own notice, one of a man whose knee had been severely wounded, and whose child was born with the same spot marked or scarred, and the other of one who was severely cut upon the cheek, and whose child was born scarred in the same place.  Mr. Darwin’s conclusion was that “the effects of injuries, especially when followed by disease, or perhaps exclusively when thus followed, are occasionally inherited.”

Let us now see what Professor Weismann has to say against this.  He writes: ­

“The only cases worthy of discussion are the well-known experiments upon guinea-pigs conducted by the French physiologist, Brown-Sequard.  But the explanation of his results is, in my opinion, open to discussion.  In these cases we have to do with the apparent transmission of artificially produced malformations. . . .  All these effects were said to be transmitted to descendants as far as the fifth or sixth generation.

“But we must inquire whether these cases are really due to heredity, and not to simple infection.  In the case of epilepsy, at any rate, it is easy to imagine that the passage of some specific organism through the reproductive cells may take place, as in the case of syphilis.  We are, however, entirely ignorant of the nature of the former disease.  This suggested explanation may not perhaps apply to the other cases; but we must remember that animals which have been subjected to such severe operations upon the nervous system have sustained a great shock, and if they are capable of breeding, it is only probable that they will produce weak descendants, and such as are easily affected by disease.  Such a result does not, however, explain why the offspring should suffer from the same disease as that which was artificially induced in the parents.  But this does not appear to have been by any means invariably the case.  Brown-Sequard himself says:  ’The changes in the eye of the offspring were of a very variable nature, and were only occasionally exactly similar to those observed in the parents.’

“There is no doubt, however, that these experiments demand careful consideration, but before they can claim scientific recognition, they must be subjected to rigid criticism as to the precautions taken, the nature and number of the control experiments, etc.

“Up to the present time such necessary conditions have not been sufficiently observed.  The recent experiments themselves are only described in short preliminary notices, which, as regards their accuracy, the possibility of mistake, the precautions taken, and the exact succession of individuals affected, afford no data on which a scientific opinion can be founded” (pp. 81, 82).

The line Professor Weismann takes, therefore, is to discredit the facts; yet on a later page we find that the experiments have since been repeated by Obersteiner, “who has described them in a very exact and unprejudiced manner,” and that “the fact” ­(I imagine that Professor Weismann intends “the facts") ­“cannot be doubted.”

On a still later page, however, we read: ­

“If, for instance, it could be shown that artificial mutilation spontaneously reappears in the offspring with sufficient frequency to exclude all possibilities of chance, then such proof [i.e. that acquired characters can be transmitted] would be forthcoming.  The transmission of mutilations has been frequently asserted, and has been even recently again brought forward, but all the supposed instances have broken down when carefully examined” .

Here, then, we are told that proof of the occasional transmission of mutilations would be sufficient to establish the fact, but on we find that no single fact is known which really proves that acquired characters can be transmitted, “for the ascertained facts which seem to point to the transmission of artificially produced diseases cannot be considered as proof.” [Italics mine.] Perhaps; but it was mutilation in many cases that Professor Weismann practically admitted to have been transmitted when he declared that Obersteiner had verified Brown-Sequard’s experiments.

That Professor Weismann recognizes the vital importance to his own theory of the question whether or no mutilations can be transmitted under any circumstances, is evident from a passage on of his work, on which he says:  “It can hardly be doubted that mutilations are acquired characters; they do not arise from any tendency contained in the germ, but are merely the reaction of the body under certain external influences.  They are, as I have recently expressed it, purely somatogenic characters ­viz. characters which emanate from the body (soma) only, as opposed to the germ-cells; they are, therefore, characters that do not arise from the germ itself.

“If mutilations must necessarily be transmitted” [which no one that I know of has maintained], “or even if they might occasionally be transmitted” [which cannot, I imagine, be reasonably questioned], “a powerful support would be given to the Lamarckian principle, and the transmission of functional hypertrophy or atrophy would thus become highly probable.”

I have not found any further attempt in Professor Weismann’s book to deal with the evidence adduced by Mr. Darwin to show that mutilations, if followed by diseases, are sometimes inherited; and I must leave it to the reader to determine how far Professor Weismann has shown reason for rejecting Mr. Darwin’s conclusion.  I do not, however, dwell upon these facts now as evidence of a transmitted change of bodily form, or of instinct due to use and disuse or habit; what they prove is that the germ-cells within the parent’s body do not stand apart from the other cells of the body so completely as Professor Weismann would have us believe, but that, as Professor Hering, of Prague, has aptly said, they echo with more or less frequency and force to the profounder impressions made upon other cells.

I may say that Professor Weismann does not more cavalierly wave aside the mass of evidence collected by Mr. Darwin and a host of other writers, to the effect that mutilations are sometimes inherited, than does Mr. Wallace, who says that, “as regards mutilations, it is generally admitted that they are not inherited, and there is ample evidence on this point.”  It is indeed generally admitted that mutilations, when not followed by disease, are very rarely, if ever, inherited; and Mr. Wallace’s appeal to the “ample evidence” which he alleges to exist on this head, is much as though he should say that there is ample evidence to show that the days are longer in summer than in winter.  “Nevertheless,” he continues, “a few cases of apparent inheritance of mutilations have been recorded, and these, if trustworthy, are difficulties in the way of the theory.” . . .  “The often-quoted case of a disease induced by mutilation being inherited (Brown-Sequard’s epileptic guinea-pigs) has been discussed by Professor Weismann and shown to be not conclusive.  The mutilation itself ­a section of certain nerves ­was never inherited, but the resulting epilepsy, or a general state of weakness, deformity, or sores, was sometimes inherited.  It is, however, possible that the mere injury introduced and encouraged the growth of certain microbes, which, spreading through the organism, sometimes reached the germ-cells, and thus transmitted a diseased condition to the offspring.”

I suppose a microbe which made guinea-pigs eat their toes off was communicated to the germ-cells of an unfortunate guinea-pig which had been already microbed by it, and made the offspring bite its toes off too.  The microbe has a good deal to answer for.

On the case of the deterioration of horses in the Falkland Islands after a few generations, Professor Weismann says: ­

“In such a case we have only to assume that the climate which is unfavourable, and nutriment which is insufficient for horses, affect not only the animal as a whole but also its germ-cells.  This would result in the diminution in size of the germ-cells, the effects upon the offspring being still further intensified by the insufficient nourishment supplied during growth.  But such results would not depend upon the transmission by the germ-cells of certain peculiarities due to the unfavourable climate, which only appear in the full-grown horse.”

But Professor Weismann does not like such cases, and admits that he cannot explain the facts in connection with the climatic varieties of certain butterflies, except “by supposing the passive acquisition of characters produced by the direct influence of climate.”

Nevertheless, in his next paragraph but one he calls such cases “doubtful,” and proposes that for the moment they should be left aside.  He accordingly leaves them, but I have not yet found what other moment he considered auspicious for returning to them.  He tells us that “new experiments will be necessary, and that he has himself already begun to undertake them.”  Perhaps he will give us the results of these experiments in some future book ­for that they will prove satisfactory to him can hardly, I think, be doubted.  He writes: ­

“Leaving on one side, for the moment, these doubtful and insufficiently investigated cases, we may still maintain that the assumption that changes induced by external conditions in the organism as a whole are communicated to the germ-cells after the manner indicated in Darwin’s hypothesis of pangenesis, is wholly unnecessary for the explanation of these phenomena.  Still we cannot exclude the possibility of such a transmission occasionally occurring, for even if the greater part of the effects must be attributable to natural selection, there might be a smaller part in certain cases which depends on this exceptional factor.”

I repeatedly tried to understand Mr. Darwin’s theory of pangenesis, and so often failed that I long since gave the matter up in despair.  I did so with the less unwillingness because I saw that no one else appeared to understand the theory, and that even Mr. Darwin’s warmest adherents regarded it with disfavour.  If Mr. Darwin means that every cell of the body throws off minute particles that find their way to the germ-cells, and hence into the new embryo, this is indeed difficult of comprehension and belief.  If he means that the rhythms or vibrations that go on ceaselessly in every cell of the body communicate themselves with greater or less accuracy or perturbation, as the case may be, to the cells that go to form offspring, and that since the characteristics of matter are determined by vibrations, in communicating vibrations they in effect communicate matter, according to the view put forward in the last chapter of my book Luck or Cunning, then we can better understand it.  I have nothing, however, to do with Mr. Darwin’s theory of pangenesis beyond avoiding the pretence that I understand either the theory itself or what Professor Weismann says about it; all I am concerned with is Professor Weismann’s admission, made immediately afterwards, that the somatic cells may, and perhaps sometimes do, impart characteristics to the germ-cells.

“A complete and satisfactory refutation of such an opinion,” he continues, “cannot be brought forward at present”; so I suppose we must wait a little longer, but in the meantime we may again remark that, if we admit even occasional communication of changes in the somatic cells to the germ-cells, we have let in the thin end of the wedge, as Mr. Darwin did when he said that use and disuse did a good deal towards modification.  Buffon, in his first volume on the lower animals, dwells on the impossibility of stopping the breach once made by admission of variation at all.  “If the point,” he writes, “were once gained, that among animals and vegetables there had been, I do not say several species, but even a single one, which had been produced in the course of direct descent from another species; if, for example, it could be once shown that the ass was but a degeneration from the horse ­then there is no farther limit to be set to the power of Nature, and we should not be wrong in supposing that with sufficient time she could have evolved all other organized forms from one primordial type.”  So with use and disuse and transmission of acquired characteristics generally ­once show that a single structure or instinct is due to habit in preceding generations, and we can impose no limit on the results achievable by accumulation in this respect, nor shall we be wrong in conceiving it as possible that all specialization, whether of structure or instinct, may be due ultimately to habit.

How far this can be shown to be probable is, of course, another matter, but I am not immediately concerned with this; all I am concerned with now is to show that the germ-cells not unfrequently become permanently affected by events that have made a profound impression upon the somatic cells, in so far that they transmit an obvious reminiscence of the impression to the embryos which they go subsequently towards forming.  This is all that is necessary for my case, and I do not find that Professor Weismann, after all, disputes it.

But here, again, comes the difficulty of saying what Professor Weismann does, and what he does not, dispute.  One moment he gives all that is wanted for the Lamarckian contention, the next he denies common sense the bare necessaries of life.  For a more exhaustive and detailed criticism of Professor Weismann’s position, I would refer the reader to an admirably clear article by Mr. Sidney H. Vines, which appeared in Nature, October 24, 1889.  I can only say that while reading Professor Weismann’s book, I feel as I do when I read those of Mr. Darwin, and of a good many other writers on biology whom I need not name.  I become like a fly in a window-pane.  I see the sunshine and freedom beyond, and buzz up and down their pages, ever hopeful to get through them to the fresh air without, but ever kept back by a mysterious something, which I feel but cannot either grasp or see.  It was not thus when I read Buffon, Erasmus Darwin, and Lamarck; it is not thus when I read such articles as Mr. Vines’s just referred to.  Love of self-display, and the want of singleness of mind that it inevitably engenders ­these, I suppose, are the sins that glaze the casements of most men’s minds; and from these, no matter how hard he tries to free himself, nor how much he despises them, who is altogether exempt?

Finally, then, when we consider the immense mass of evidence referred to briefly, but sufficiently, by Mr. Charles Darwin, and referred to without other, for the most part, than off-hand dismissal by Professor Weismann in the last of the essays that have been recently translated, I do not see how anyone who brings an unbiased mind to the question can hesitate as to the side on which the weight of testimony inclines.  Professor Weismann declares that “the transmission of mutilations may be dismissed into the domain of fable.” If so, then, whom can we trust?  What is the use of science at all if the conclusions of a man as competent as I readily admit Mr. Darwin to have been, on the evidence laid before him from countless sources, is to be set aside lightly and without giving the clearest and most cogent explanation of the why and wherefore?  When we see a person “ostrichizing” the evidence which he has to meet, as clearly as I believe Professor Weismann to be doing, we shall in nine cases out of ten be right in supposing that he knows the evidence to be too strong for him.