CHAPTER XIII.. Human Population in the Future.

HUMAN POPULATION IN THE FUTURE.

§ 371. Any further evolution in the most highly-evolved of terrestrial beings, Man, must be of the same nature as evolution in general. Structurally considered, it may consist in greater integration, or greater differentiation, or both--augmented bulk, or increased heterogeneity and definiteness, or a combination of the two. Functionally considered, it may consist in a larger sum of actions, or more multiplied varieties of actions, or both--a larger amount of sensible and insensible motion generated, or motions more numerous in their kinds and more intricate and exact in their co-ordinations, or motions that are greater alike in quantity, complexity, and precision.

Expressing the change in terms of that more special evolution displayed by organisms; we may say that it must be one which further adapts the moving equilibrium of organic actions. As was pointed out in First Principles, § 173, “the maintenance of such a moving equilibrium, requires the habitual genesis of internal forces corresponding in number, directions, and amounts to the external incident forces--as many inner functions, single or combined, as there are single or combined outer actions to be met.” And it was also pointed out that “the structural complexity accompanying functional equilibration, is definable as one in which there are as many specialized parts as are capable, separately and jointly, of counteracting the separate and joint forces amid which the organism exists.” Clearly, then, since all incompletenesses in Man as now constituted, are failures to meet certain of the outer actions (mostly involved, remote, irregular), to which he is exposed; every advance implies additional co-ordinations of actions and accompanying complexities of organization.

Or, to specialize still further this conception of future progress, we may consider it as an advance towards completion of that continuous adjustment of internal to external relations, which Life shows us. In Part I. of this work, where it was shown that the correspondence between inner and outer actions which under its phenomenal aspect, we call Life, is a particular kind of what, in terms of Evolution, we called a moving equilibrium; it was shown that the degree of life varies as the degree of correspondence. Greater evolution or higher life implies, then, such modifications of human nature as shall make more exact the existing correspondences, or shall establish additional correspondences, or both. Connexions of phenomena of a rare, distant, unobtrusive, or intricate kind, which we either suffer from or do not take advantage of, have to be responded to by new connexions of ideas, and acts properly combined and proportioned: there must be increase of knowledge, or skill, or power, or of all these. And to effect this more extensive, more varied, and more accurate, co-ordination of actions, there must be organization of still greater heterogeneity and definiteness.

§ 372. Let us, before proceeding, consider in what particular ways this further evolution, this higher life, this greater co-ordination of actions, may be expected to show itself.

Will it be in strength? Probably not to any considerable degree. Mechanical appliances are fast supplanting brute force, and doubtless will continue doing this. Though at present civilized nations largely depend for self-preservation on vigour of limb, and are likely to do so while wars continue; yet that progressive adaptation to the social state which must at last bring wars to an end, will leave the amount of muscular power to adjust itself to the requirements of a peaceful regime. Though, taking all things into account, the muscular power then required may not be less than now, there seems no reason why more should be required.

Will it be swiftness or agility? Probably not. In savages these are important elements of the ability to maintain life; but in civilized men they aid self-preservation in quite minor degrees, and there seems no circumstance likely to necessitate an increase of them. By games and gymnastic competitions, such attributes may indeed be artificially increased; but no artificial increase which does not bring a proportionate advantage can be permanent; since, other things equal, individuals and societies that devote the same amounts of energy in ways which subserve life more effectually, must by and by predominate.

Will it be in mechanical skill, that is, in the better-co-ordination of complex movements? Most likely in some degree. Awkwardness is continually entailing injuries and deaths. Moreover the complicated tools which civilization brings into use, are constantly requiring greater delicacy of manipulation. All the arts, industrial and æsthetic, as they develop, imply a corresponding development of perceptive and executive faculties in men: the two act and react.

Will it be in intelligence? Largely, no doubt. There is ample room for advance in this direction, and ample demand for it. Our lives are universally shortened by our ignorance. In attaining complete knowledge of our own natures and of the natures of surrounding things--in ascertaining the conditions of existence to which we must conform, and in discovering means of conforming to them under all variations of seasons and circumstances; we have abundant scope for intellectual progress.

Will it be in morality, that is, in greater power of self-regulation? Largely also: perhaps most largely. Right conduct is usually come short of more from defect of will than defect of knowledge. For the right co-ordination of those complex actions which constitute human life in its civilized form, there goes not only the pre-requisite--recognition of the proper course; but the further pre-requisite--a due impulse to pursue that course. On calling to mind our daily failures to fulfil often-repeated resolutions, we shall perceive that lack of the needful desire, rather than lack of the needful insight, is the chief cause of faulty action. A further endowment of those feelings which civilization is developing in us--sentiments responding to the requirements of the social state--emotive faculties that find their gratifications in the duties devolving on us--must be acquired before the crimes, excesses, diseases, improvidences, dishonesties, and cruelties, that now so greatly diminish the duration of life, can cease.

Thus, looking at the several possibilities, and asking what direction this further evolution, this more complete moving equilibrium, this better adjustment of inner to outer relations, this more perfect co-ordination of actions, is likely to take; we conclude that it must take mainly the direction of a higher intellectual and emotional development.

§ 373. This conclusion we shall find equally forced on us if we inquire for the causes which are to bring about such results. No more in the case of Man than in the case of any other being, can we presume that evolution has taken place, or will hereafter take place, spontaneously. In the past, at present, and in the future, all modifications, functional and organic, have been, are, and must be, immediately or remotely consequent on surrounding conditions. What, then, are those changes in the environment to which, by direct or indirect equilibration, the human organism has been adjusting itself, is adjusting itself now, and will continue to adjust itself? And how do they necessitate a higher evolution of the organism?

Civilization, everywhere having for its antecedent the increase of population, and everywhere having for one of its consequences a decrease of certain race-destroying forces, has for a further consequence an increase of certain other race-destroying forces. Danger of death from predatory animals lessens as men grow more numerous. Though, as they spread over the Earth and divide into tribes, men become wild beasts to one another, yet the danger of death from this cause also diminishes as tribes coalesce into nations. But the danger of death which does not diminish, is that produced by augmentation of numbers itself--the danger from deficiency of food. Supposing human nature to remain unchanged, the mortality hence resulting would, on the average, rise as human beings multiplied. If mortality, under such conditions, does not rise, it must be because the supply of food also augments; and this implies some change in human habits wrought by stress of human needs. Here, then, is the permanent cause of modification to which civilized men are exposed. Though the intensity of its action is ever being mitigated in one direction by greater production of food, it is, in the other direction, ever being added to by the greater production of individuals. Manifestly, the wants of their redundant numbers constitute the only stimulus mankind have to obtain more necessaries of life. Were not the demand beyond the supply, there would be no motive to increase the supply. And manifestly, this excess of demand over supply is perennial: this pressure of population, of which it is the index, cannot be eluded. Though by the emigration that takes place when the pressure arrives at a certain intensity, temporary relief is from time to time obtained; yet as, by this process, all habitable countries must become peopled, it follows that in the end the pressure, whatever it may then be, must be borne in full.

This constant increase of people beyond the means of subsistence causes, then, a never-ceasing requirement for skill, intelligence, and self-control--involves, therefore, a constant exercise of these and gradual growth of them. Every industrial improvement is at once the product of a higher form of humanity, and demands that higher form of humanity to carry it into practice. The application of science to the arts, is the bringing to bear greater intelligence for satisfying our wants, and implies continued progress of that intelligence. To get more produce from the acre, the farmer must study chemistry, must adopt new mechanical appliances, and must, by the multiplication of processes, cultivate both his own powers and the powers of his labourers. To meet the requirements of the market, the manufacturer is perpetually improving his old machines and inventing new ones; and by the premium of high wages incites artizans to acquire greater skill. The daily-widening ramifications of commerce entail on the merchant a need for more knowledge and more complex calculations; while the lessening profits of the ship-owner force him to build more scientifically, to get captains of higher intelligence and better crews. In all cases pressure of population is the original cause. Were it not for the competition this entails, more thought and energy would not daily be spent on the business of life; and growth of mental power would not take place. Difficulty in getting a living is alike the incentive to a higher education of children, and to a more intense and long-continued application in adults. In the mother it prompts foresight, economy, and skilful house-keeping; in the father, laborious days and constant self-denial. Nothing but necessity could make men submit to this discipline; and nothing but this discipline could produce a continued progression.

In this case, as in many others, Nature secures each step in advance by a succession of trials; which are perpetually repeated, and cannot fail to be repeated, until success is achieved. All mankind in turn subject themselves more or less to the discipline described; they either may or may not advance under it; but, in the nature of things, only those who do advance under it eventually survive. For, necessarily, families and races whom this increasing difficulty of getting a living which excess of fertility entails, does not stimulate to improvements in production--that is, to greater mental activity--are on the high road to extinction; and must ultimately be supplanted by those whom the pressure does so stimulate. This truth we have recently seen exemplified in Ireland. And here, indeed, without further illustration, it will be seen that premature death, under all its forms and from all its causes, cannot fail to work in the same direction. For as those prematurely carried off must, in the average of cases, be those in whom the power of self-preservation is the least, it unavoidably follows that those left behind to continue the race, must be those in whom the power of self-preservation is the greatest--must be the select of their generation. So that, whether the dangers to existence be of the kind produced by excess of fertility, or of any other kind, it is clear that by the ceaseless exercise of the faculties needed to contend with them, and by the death of all men who fail to contend with them successfully, there is ensured a constant progress towards a higher degree of skill, intelligence, and self-regulation--a better co-ordination of actions--a more complete life.

§ 374. The proposition at which we have thus arrived is, then, that excess of fertility, through the changes it is ever working in Man’s environment, is itself the cause of Man’s further evolution; and the obvious corollary here to be drawn is, that Man’s further evolution so brought about, itself necessitates a decline in his fertility.

All future progress in civilization which the never-ceasing pressure of population must produce, will be accompanied by an enhanced cost of Individuation, both in structure and function; and more especially in nervous structure and function. The peaceful struggle for existence in societies ever growing more crowded and more complicated, must have for its concomitant an increase of the great nervous centres in mass, in complexity, in activity. That larger body of emotion needed as a fountain of energy for men who have to hold their places and rear their families under the intensifying competition of social life, is, other things equal, the correlative of larger brain. Those higher feelings presupposed by the better self-regulation which, in a better society, can alone enable the individual to leave a persistent posterity, are, other things equal, the correlatives of a more complex brain; as are also those more numerous, more varied, more general, and more abstract ideas, which must also become increasingly requisite for successful life as society advances. And the genesis of this larger quantity of feeling and thought, in a brain thus augmented in size and developed in structure, is, other things equal, the correlative of a greater wear of nervous tissue and greater consumption of materials to repair it. So that both in original cost of construction and in subsequent cost of working, the nervous system must become a heavier tax on the organism. Already the brain of the civilized man is larger by nearly thirty per cent. than the brain of the savage. Already, too, it presents an increased heterogeneity--especially in the distribution of its convolutions. And further changes like these which have taken place under the discipline of civilized life, we infer will continue to take place. But everywhere and always, evolution is antagonistic to procreative dissolution. Whether it be in greater growth of the organs which subserve self-maintenance, whether it be in their added complexity of structure, or whether it be in their higher activity, the abstraction of the required materials implies a diminished reserve of materials for race-maintenance. And we have seen reason to believe that this antagonism between Individuation and Genesis, becomes unusually marked where the nervous system is concerned, because of the costliness of nervous structure and function. In § 346 was pointed out the apparent connexion between high cerebral development and prolonged delay of sexual maturity; and in §§ 366, 367, the evidence went to show that where exceptional fertility exists there is sluggishness of mind, and that where there has been during education excessive expenditure in mental action, there frequently follows a complete or partial infertility. Hence the particular kind of further evolution which Man is hereafter to undergo, is one which, more than any other, may be expected to cause a decline in his power of reproduction.

The higher nervous development and greater expenditure in nervous action, here described as indirectly brought about by increase of numbers, and as thereafter becoming a check on the increase of numbers, must not be taken to imply an intenser strain--a mentally-laborious life. The greater emotional and intellectual power and activity above contemplated, must be understood as becoming, by small increments, organic, spontaneous, and pleasurable. As, even when relieved from the pressure of necessity, large-brained Europeans voluntarily enter on enterprises and activities which the savage could not keep up even to satisfy urgent wants; so, their still larger-brained descendants will, in a still higher degree, find their gratifications in careers entailing still greater mental expenditures. This enhanced demand for materials to establish and carry on the psychical functions, will be a constitutional demand. We must conceive the type gradually so modified, that the more-developed nervous system irresistibly draws off, for its normal and unforced activities, a larger proportion of the common stock of nutriment; and while so increasing the intensity, completeness, and length of the individual life, necessarily diminishing the reserve applicable to the setting up of new lives--no longer required to be so numerous.

Though the working of this process will doubtless be interfered with and modified in the future, as it has been in the past, by the facilitations of living which civilization brings; yet nothing beyond temporary interruptions can so be caused. However much the industrial arts may be improved, there must be a limit to the improvement; while, with a rate of multiplication in excess of the rate of mortality, population must continually tread on the heels of production. So that though, during the earlier stages of civilization, an increased amount of food may accrue from a given amount of labour, there must come a time when this relation will be reversed, and when every additional increment of food will be obtained by a more than proportionate labour: the disproportion growing ever higher, and the diminution of the reproductive power becoming greater.

§ 375. There now remains but to inquire towards what limit this progress tends. So long as the fertility of the race is more than sufficient to balance the diminution by deaths, population must continue to increase. So long as population continues to increase, there must be pressure on the means of subsistence. And so long as there is pressure on the means of subsistence, further mental development must go on, and further diminution of fertility must result; provided that the actions and reactions which have been described are not artificially interfered with. I append this qualifying clause advisedly, and especially emphasize it, because these actions and reactions have been hitherto, and are now, greatly interfered with by governments, and the continuance of the interferences may retard, if not stop, that further evolution which would else go on.

I refer to those hindrances to the survival of the fittest which in earlier times resulted from the undiscriminating charities of monasteries and in later times from the operation of Poor Laws. Of course if the competition which increasing pressure of population entails, is prevented from acting on a considerable part of the community, such part, saved from the needed intellectual and moral stress, will not undergo any further mental development; and must ever tend to leave a posterity, and an increasing posterity, in which none of that higher individuation which checks genesis takes place. Such State-meddlings with the natural play of actions and reactions produce a further evil equally great or greater. For those who are not self-maintained, or but partially self-maintained, are supplied with the means they lack by the better members of the community; and these better members have thus not only to support themselves and their offspring, but also to support or aid the inferior members and their offspring. The under-working of one part is accompanied by the over-working of the other part--by a working which at each stage of progress exceeds that which the normal conditions necessitate, and results sometimes in illness, premature age, or death, or in lessened number of children, or in imperfect rearing of children: the bad are fostered and the good are repressed.

It does not follow that the struggle for life and the survival of the fittest must be left to work out their effects without mitigation. It is contended only that there shall not be a forcible burdening of the superior for the support of the inferior. Such aid to the inferior as the superior voluntarily yield, kept as it will be within moderate limits, may be given with benefit to both--relief to the one, moral culture to the other. And aid willingly given (little to the least worthy and more to the most worthy) will usually be so given as not to further the increase of the unworthy. For in proportion as the emotional nature becomes more evolved, and there grows up a higher sense of parental responsibility, the begetting of children that cannot be properly reared will be universally held intolerable. If, as we see, public opinion in many places and times becomes coercive enough to force men to fight duels, we can scarcely doubt that at a higher stage of evolution it may become so coercive as to prevent men from marrying improvidently. If the frowns of their fellows can make men commit immoral acts, surely they may make men refrain from immoral acts--especially when the actors themselves feel that the threatened frowns would be justified. Hence with a higher moral nature will come a restriction on the multiplication of the inferior.

In brief, the sole requirement is that there shall be no extensive suspension of that natural relation between merit and benefit which constitutes justice. Holding, then, that this all-essential condition will itself come to be recognized and enforced by a more evolved humanity, let us consider what is the goal towards which the restraint on genesis by individuation progresses.

§ 375a. Supposing the Sun’s light and heat, on which all terrestrial life depends, to continue abundant for a period long enough to allow the entire evolution we are contemplating; there are still certain changes which must prevent such complete adjustment of human nature to surrounding conditions, as would permit the rate of multiplication to become equal to the rate of mortality. As before pointed out (§ 148), during an epoch of 21,000 years each hemisphere goes through a cycle of temperate seasons and seasons extreme in their heat and cold--variations which are themselves alternately exaggerated and mitigated in the course of far longer cycles; and we saw that these cause perpetual ebbings and flowings of species over different parts of the Earth’s surface. Further, by slow but inevitable geologic changes, especially those of elevation and subsidence, the climate and physical characters of every habitat are modified; while old habitats are destroyed and new are formed. This, too, we noted as a constant cause of migrations and of resulting alterations of environment. Now though the human race differs from other races in having a power of artificially counteracting external changes, yet there are limits to this power; and, even were there no limits, the changes could not fail to work their effects indirectly, if not directly. If, as is thought probable, these astronomic cycles entail recurrent glacial periods in each hemisphere, then parts of the Earth which are at one time thickly peopled, will at another time be almost deserted, and vice versâ. The geologically-caused alterations of climate and surface, must produce further slow re-distributions of population; and other currents of people, to and from different regions, will be necessitated by the rise of successive centres of higher civilization. Consequently, mankind cannot but continue to undergo changes of environment, physical and moral, analogous to those which they have thus far been undergoing. Such changes may eventually become slower and less marked; but they can never cease. And if they can never cease there can never arise a perfect adaptation of human nature to its conditions of existence. To establish that complete correspondence between inner and outer actions which constitutes the highest life and greatest power of self-preservation, there must be a prolonged converse between the organism and circumstances which remain the same. If the external relations are being altered while the internal relations are being adjusted to them, the adjustment can never become exact. And in the absence of exact adjustment, there cannot exist that theoretically-highest power of self-preservation with which there would co-exist the theoretically-lowest power of race-production.

Hence though the number of premature deaths may ultimately become very small, it can never become so small as to allow the average number of offspring from each pair to fall so low as two. Some average number between two and three may be inferred as the limit--a number, however, which is not likely to be quite constant, but may be expected at one time to increase somewhat and afterwards to decrease somewhat, according as variations in physical and social conditions lower or raise the cost of self-preservation.

To this qualification must be added a further qualification. The foregoing argument tacitly assumes that the causes described will continuously operate on all mankind; whereas a survey of the facts makes it clear that some parts only of the Earth’s surface are capable of bearing high types of civilization, and consequently high types of Man. There must remain hereafter, as there are now, considerable parts of its surface which can support only groups of nomads, or other groups obliged by their habitats to lead simple and inferior kinds of life. Only by subjection to the discipline we have been contemplating can there be produced the fully-developed Man; and evidently in many parts of the world this discipline will continue to be eluded. Not only must we conclude that the varieties of our race now living in desert regions and arctic climates will continue hereafter to do so, but we may conclude that always, as now, a certain proportion of men who are born in civilized societies, impatient of the stress which pressure of population puts on them, will escape into unoccupied or sparsely-peopled regions, where they can lead unrestrained lives though lives of hardship. Recognizing as we must the probability that in common with all other things, humanity will continue to differentiate and produce a more heterogeneous assemblage of types, we must infer that only in some of the highest of these will the antagonism of individuation and genesis have the anticipated effects.

Restricting ourselves to these, then, we may conclude that in the end, pressure of population and its accompanying evils will almost disappear; and will leave a state of things requiring from each individual little more than a normal and pleasurable activity. Cessation in the decrease of fertility implies cessation in the development of the nervous system; and this implies a nervous system which has become equal to all that is demanded of it--has not to do more than is natural to it. But that exercise of faculties which does not exceed what is natural, constitutes gratification.

The necessary antagonism of Individuation and Genesis, not only, then, fulfils the à priori law of maintenance of race, from the monad up to Man, but ensures final attainment of the highest form of this maintenance--a form in which the amount of life shall be the greatest possible and the births and deaths the fewest possible. From the beginning pressure of population has been the proximate cause of progress. It produced the original diffusion of the race. It compelled men to abandon predatory habits and take to agriculture. It led to the clearing of the Earth’s surface. It forced men into the social state; made social organization inevitable; and has developed the social sentiments. It has stimulated to progressive improvements in production, and to increased skill and intelligence. It is daily thrusting us into closer contact and more mutually-dependent relationships. And after having caused, as it ultimately must, the due peopling of the globe, and the raising of its habitable parts into the highest state of culture--after having perfected all processes for the satisfaction of human wants--after having, at the same time, developed the intellect into competence for its work, and the feelings into fitness for social life--after having done all this, the pressure of population must gradually approach to an end--an end, however, which for the reasons given it cannot absolutely reach.

§ 377. In closing the argument let us not overlook the self-sufficingness of those universal processes by which the results reached thus far have been wrought out, and which may be expected to work out these future results.

Evolution under all its aspects, general and special, is an advance towards equilibrium. We have seen that the theoretical limit towards which the integration and differentiation of every aggregate advances, is a state of balance between all the forces to which its parts are subject, and the forces which its parts oppose to them (First Prin. § 170). And we have seen that organic evolution is a progress towards a moving equilibrium completely adjusted to environing actions.

It has been also pointed out that, in civilized Man, there is going on a new class of equilibrations--those between his actions and the actions of the societies he forms (First Prin. § 175). Social restraints and requirements are ever altering his activities and by consequence his nature; and as fast as his nature is altered, social restraints and requirements undergo more or less re-adjustment. Here the organism and the conditions are both modifiable; and by successive conciliations of the two, there is effected a progress towards equilibrium.

More recently we have seen that in every species, there establishes itself an equilibrium of an involved kind between the total race-destroying forces and the total race-preserving forces--an equilibrium which implies that where the ability to maintain individual life is small, the ability ta propagate must be great, and vice versâ. Whence it follows that the evolution of a race more in equilibrium with the environment, is also the evolution of a race in which there is a correlative approach towards equilibrium between the number of new individuals produced and the number which survive and propagate.

The final result to be observed is that in Man, all these equilibrations between constitution and conditions, between the structure of society and the nature of its members, between fertility and mortality, advance simultaneously towards a common climax. In approaching an equilibrium between his nature and the ever-varying circumstances of his inorganic environment, and in approaching an equilibrium between his nature and all the requirements of the social state, Man is at the same time approaching that lowest limit of fertility at which the equilibrium of population is maintained by the addition of as many infants as there are subtractions by death in old age. But in a universe of which all parts are in motion and every part is consequently subject to change of conditions, neither this equilibrium nor any other equilibrium can become complete.

THE END.

APPENDICES.

APPENDIX A.

SUBSTITUTION OF AXIAL FOR FOLIAR ORGANS IN PLANTS.

I append here the evidences referred to in § 190. The most numerous and striking I have met with among the Umbelliferæ. Monstrosities having the alleged implication, are frequent in the common Cow-Parsnep--so frequent that they must be familiar to botanists; and wild Angelica supplies many over-developments of like meaning. Omitting numerous cases of more or less significance, I will limit myself to two.

One of them is that of a terminal umbel, in which nine of the outer umbellules are variously transformed--here a single flower being made monstrous by the development of some of its members into buds; there several such malformed flowers being associated with rays that bear imperfect umbellules; and elsewhere, flowers being replaced by umbellules: some of which are perfect, and others imperfect only in the shortness of the flower-stalks. The annexed Fig. 69, representing in a somewhat conventionalized way, a part of the dried specimen, will give an idea of this Angelica. At a is shown a single flower partially changed; in the umbellule marked b, one of the rays bears a secondary umbellule; and there may be seen at c and d, several such over-developments.

But the most conclusive instance is that of a Cow-Parsnep, in which a single terminal umbel, besides the transformations already mentioned, exhibits higher degrees of such transformations. The components of this complex growth are;--three central umbellules, abnormal only in minor points; one umbellule, external to these, which is partially changed into an umbel; one rather more out of the centre, which is so far metamorphosed as to be more an umbel than an umbellule: nine peripheral clusters formed by the development of umbellules into umbels, some of which are partially compounded still further. Examined in detail, these structures present the following facts:--1. The innermost umbellule is normal, save in having a peripheral flower of which one member (apparently a petal) is transformed into a flower-bud. 2. The next umbellule, not quite so central, has one of its peripheral flowers made monstrous by the growth of a bud from the base of the calyx. 3. The third of the central umbellules has two abnormal outer flowers. One of them carries a flower-bud on its edge, in place of a foliar member. The other is half flower and half umbellule: being composed of three petals, three stamens, and five flower-buds growing where the other petals and stamens should grow. 4. Outside of these umbellules comes one of the mixed clusters. Its five central flowers are normal. Surrounding these are several flowers transformed in different degrees: one having a stamen partially changed into a flower bud. And then, at the periphery of this mixed cluster, come three complete umbellules and an incomplete one in which some petals and stamens of the original flower remain. 5. A mixed cluster, in which the umbel-structure predominates, stands next. Its three central flowers are normal. Surrounding them are five flowers over-developed in various ways, like those already described. And on its periphery are seven complete umbellules in place of flowers; besides an incomplete umbellule that contains traces of the original flower, one of them being a petal imperfectly twisted up into a bud. 6. Of the nine external clusters, in which the development of simple into compound umbels is most decided, nearly all present anomalies. Three of them have each a central flower untransformed; and in others, the central umbellule is composed of two, three, or four flowers. 7. But the most remarkable fact is, that in sundry of these peripheral clusters, resulting from the metamorphosis of simple umbels into compound umbels, the like metamorphosis is carried a stage higher. Some of the component rays, are themselves the bearers of compound umbels instead of simple umbels. In Fig. 70, a portion of the dried specimen is represented. Two of the central umbellules are marked a and b; those marked c and d are mixed clusters; at e and f are compound umbels replacing simple ones; and g shows one of the rays on which the over-development goes still further.

Does not this evidence, enforced as it is by much more of like kind, go far to prove that foliar organs may be developed into axial organs? Even were not the transitional forms traceable, there would still, I think, be no other legitimate interpretation of the facts last detailed. The only way of eluding the conclusion here drawn, is by assuming that where a cluster of flowers replaces a single flower, it is because the axillary buds which hypothetically belong to the several foliar organs of the flower, become developed into axes; and assuming this, is basing an hypothesis on another hypothesis that is directly at variance with facts. The foliar organs of flowers do not bear buds in their axils; and it would never have been supposed that such buds are typically present, had it not been for that mistaken conception of “type” which has led to many other errors in Biology. Goethe writes: “Now as we cannot realize the idea of a leaf apart from the node out of which it springs, or of a node without a bud, we may venture to infer,” &c. See here an example of a method of philosophizing not uncommon among the Germans. The method is this--Survey a portion of the facts, and draw from them a general conception; project this general conception back into the objective world, as a mould in which Nature casts her products; expect to find it everywhere fulfilled; and allege potential fulfilment where no actual fulfilment is visible.

If instead of imposing our ideal forms on Nature, we are content to generalize the facts as Nature presents them, we shall find no warrant for the morphological doctrine above enunciated. The only conception of type justified by the logic of science, is--that correlation of parts which remains constant under all modifications of the structure to be defined. To ascertain this, we must compare all these modifications, and note what traits are common to them. On doing so with the successive segments of a phænogamic axis, we are brought to a conclusion widely different from that of Goethe. Axillary buds are almost universally absent from the cotyledons; they are habitually present in the axils of fully-developed leaves higher up the axis; they are often absent from leaves that are close to the flower; they are nearly always absent from the bracts; absent from the sepals; absent from the petals; absent from the stamens; absent from the carpels. Thus, out of eight leading forms which folia assume, one has the axillary bud and seven are without it. With these facts before us, it seems to me not difficult to “realize the idea” “of a node without a bud.” If we are not possessed by a foregone conclusion, the evidence will lead us to infer, that each node bears a foliar appendage and may bear an axillary bud.

Even, however, were it granted that the typical segment of a Phænogam includes an axillary bud, which must be regarded as always potentially present, no legitimate counter-interpretation of the monstrosities above described could thence be drawn. If when an umbellule is developed in place of a flower, the explanation is, that its component rays are axillary to the foliar organs of the flower superseded; we may fairly require that these foliar organs to which they are axillary, shall be shown. But there are none. In the last specimen figured, the inner rays of each such umbellule are without them; most of the outer rays are also without them; and in one cluster, only a single ray has a bract at its point of origin. There is a rejoinder ready, however: the foliar organs are said to be suppressed. Though Goethe could not “realize the idea” “of a node without a bud,” those who accept his typical form appear to find no difficulty in realizing the idea of an axillary bud without anything to which it is axillary. But letting this pass, suppose we ask what is the warrant for this assumed suppression. Axillary buds normally occur where the nutrition is high enough to produce fully-developed leaves; and when axillary buds are demonstrably present in flowers, they accompany foliar organs that are more leaf-like than usual--always greener if not always larger. That is to say, the normal and the abnormal axillary buds, are alike the concomitants of foliar organs coloured by that chlorophyll which habitually favours foliar development. How, then, can it be supposed that when, out of a flower there is developed a cluster of flower-bearing rays, the implied excess of nutrition causes the foliar organs to abort? It is true that very generally in a branched inflorescence, the bracts of the several flower-branches are very small (their smallness being probably due to that defective supply of certain chlorophyll-forming matters, which is the proximate cause of flowering); and it is true that, under these conditions, a flowering axis of considerable size, for the development of which chlorophyll is less needful, grows from the axil of a dwarfed leaf. But the inference that the foliar organ may therefore be entirely suppressed, seems to me irreconcilable with the fact, that the foliar organ is always developed to some extent before the axillary bud appears. Until it has been shown that in some cases a lateral bud first appears, and a foliar organ afterwards grows out beneath it, to form its axil, the conception of an axillary bud of which the foliar organ is suppressed, will remain at variance with the established truths of development.

* * * * *

The above originally formed a portion of § 190. I have transferred it to the Appendix, partly because it contains too much detail to render it fit for the general argument, and partly because the interpretations being open to some question, it seemed undesirable to risk compromising that argument by including them. The criticisms passed upon these interpretations have not, however, sufficed to convince me of their incorrectness. Unfortunately, I have since had no opportunity of verifying the above statements by microscopic examinations, as I had intended.

Though unable to enforce the inference drawn by further facts more minutely looked into, I may add some arguments based on facts that are well known. One of these is the fact that the so-called axillary bud is not universally axillary--is not universally seated in the angle made by the axis and an appended foliar organ. In certain plants the axillary bud is placed far above the node, half-way between it and the succeeding node. So that not only may a segment of a phæenogamic axis be without the axillary bud, but the axillary bud, when present, may be removed from that place in which, according to Goethe, it necessarily exists. Another fact not congruous with the current doctrine, is the common occurrence of “adventitious” buds--the buds that are put out from roots and from old stems or branches bare of leaves. The name under which they are thus classed, is meant to imply that they may be left out of consideration. Those, however, who have not got a theory to save by putting anomalies out of sight, may be inclined to think that the occurrence of buds where they are avowedly unconnected with nodes, and are axillary to nothing, tells very much against the assumption that every bud implies a node and a corresponding foliar organ. And they may also see that the development of these adventitious buds at places where there is excess of nutritive materials, favours the view above set forth. For if a bud thus arises at a place where it is not morphologically accounted for, simply because there happens to be at that place an abundance of unorganized protoplasm; then, clearly, it is likely that if the mass of protoplasm from which a leaf would usually arise, is greatly increased in mass by excess of nutrition, it may develop into an axis instead of a leaf.

* * * * *

Many years after this work was published, I discovered among my papers a memorandum which unfortunately I had overlooked, containing further evidence in support of the foregoing conclusion. With the omission of an error concerning the species of plant, I reproduce this memorandum just as it stood:--

“I found at Dieppe, July 1, 1860, in a garden near the sea a sample of cultivated wild flower (I thought it was grown as an ornamental flower) in which some of the single flowers of the umbel were developed into groups of flowers thus:--

“In the case where the transformation was fully effected the umbellule had six flowers, answering to the six petals of the original flowers. In other cases the transformation was incomplete. There were instances where but two of the petals were developed into flowers; and the other petals remained unchanged. Others in which three were developed; and others where four were developed. In some cases, too, the development of a petal into a flower was imperfect, in the absence of the flower-stalk--the flowers were sessile in the place where the petals would have been. In one case there was an imperfect flower sessile; another imperfect flower on a short stalk; and three perfect flowers on long stalks.

“I was in some doubt whether the petals or the stamens were developed. In cases of imperfect transformation the petals at the base of the umbellule seemed to stand in the position of calyx or involucrum, giving the idea that the stamens were developed into flowers. But in the case where there were six flowers developed there were no petals at the base.

“That it was a matter of extra nutrition was shown by this:--

“1. That they were cultivated as garden flowers.

“2. That where there was one perfectly developed umbellule, it was the only one in the umbel.

“3. That where there were three umbellules they were all imperfect.

“4. That in this imperfect umbellule the perfect flowers were on long stalks and the imperfect ones sessile.

“5. That the umbellules were on stalks both longer and thicker than those of single flowers.”

* * * * *

“You have quoted sufficient evidence in the text (§ 190) to establish the conclusion that no sharp line can be drawn between axes and leaf-structure; and a very great deal more could be added in the same sense. Petioles for instance, exist which the most highly trained histological observer could not distinguish from stems.

“But I must demur to the suggestion that the replacement of one by the other is primarily a question of nutrition. We are as ignorant as ever of the proximate cause of the production of a leaf or a shoot at a certain spot in meristematic tissue.”

To this last remark I had at first made only the reply that the plants exhibiting the abnormalities were in all cases excessively luxuriant in their growths; but to this I am now able to add a more definite reply. The expert from whom I have just quoted, had read this appendix before there had been made to it the above addition describing the flower from Dieppe; and I was not myself aware, until I came to read over this addition, what clear evidence it contains that extra nutrition was the cause of these transformations of foliar structures into axial structures; but the above paragraphs 1, 2, 3, 4, 5, contain different evidences conspiring to prove this.]

APPENDIX B.

A CRITICISM ON PROF. OWEN’S THEORY OF THE VERTEBRATE SKELETON.

I. On the Archetype and Homologies of the Vertebrate Skeleton. By RICHARD OWEN, F.R.S.--London, 1848. pp. 172.

II. Principes d’Ostéologie Comparée, ou Recherches sur l’Archétype et les Homologies du Squelette Vertébré. Par RICHARD OWEN.--Paris.

Principles of Comparative Osteology; or, Researches on the Archetype and the Homologies of the Vertebrate Skeleton. By RICHARD OWEN.

III. On the Nature of Limbs. A Discourse delivered on Friday, February 9, at an Evening Meeting of the Royal Institution of Great Britain. By RICHARD OWEN, F.R.S.--London, 1849. pp. 119.

Judging whether another proves his position is a widely different thing from proving your own. To establish a general law requires an extensive knowledge of the phenomena to be generalized; but to decide whether an alleged general law is established by the evidence assigned, requires merely an adequate reasoning faculty. Especially is such a decision easy where the premises do not warrant the conclusion. It may be dangerous for one who has but little previous acquaintance with the facts, to say that a generalization is demonstrated; seeing that the argument may be one-sided: there may be many facts unknown to him which disprove it. But it is not dangerous to give a negative verdict when the alleged demonstration is manifestly insufficient. If the data put before him do not bear out the inference, it is competent for every logical reader to say so.

From this standpoint, then, we venture to criticize some of Professor Owen’s osteological theories. For his knowledge of comparative osteology we have the highest respect. We believe that no living man has so wide and detailed an acquaintance with the bony structure of the Vertebrata. Indeed, there probably has never been any one whose information on the subject was so nearly exhaustive. Moreover, we confess that nearly all we know of this department of biology has been learnt from his lectures and writings. We pretend to no independent investigations, but merely to such knowledge of the phenomena as he has furnished us with. Our position, then, is such that, had Professor Owen simply enunciated his generalizations, we should have accepted them on his authority. But he has brought forward evidence to prove them. By so doing he has tacitly appealed to the judgments of his readers and hearers--has practically said, “Here are the facts; do they not warrant these conclusions?” And all we propose to do, is to consider whether the conclusions are warranted by the facts brought forward.

Let us first limit the scope of our criticisms. On that division of comparative osteology which deals with what Professor Owen distinguishes as “special homologies,” we do not propose to enter. That the wing of a bird is framed upon bones essentially parallel to those of a mammal’s fore-limb; that the cannon-bone of a horse’s leg answers to the middle metacarpal of the human hand; that various bones in the skull of a fish are homologous with bones in the skull of a man--these and countless similar facts, we take to be well established. It may be, indeed, that the doctrine of special homologies is at present carried too far. It may be that, just as the sweeping generalization at one time favoured, that the embryonic phases of the higher animals represent the adult forms of lower ones, has been found untrue in a literal sense, and is acceptable only in a qualified sense; so the sweeping generalization that the skeletons of all vertebrate animals consist of homologous parts, will have to undergo some modification. But that this generalization is substantially true, all comparative anatomists agree.

The doctrine which we are here to consider, is quite a separate one--that of “general homologies.” The truth or falsity of this may be decided on quite apart from that of the other. Whether certain bones in one vertebrate animal’s skeleton correspond with certain bones in another’s, or in every other’s, is one question; and whether the skeleton of every vertebrate animal is divisible into a series of segments, each of which is modelled after the same type, is another question. While the first is answered in the affirmative, the last may be answered in the negative; and we propose to give reasons why it should be answered in the negative.

* * * * *

In so far as his theory of the skeleton is concerned, Professor Owen is an avowed disciple of Plato. At the conclusion of his Archetype and Homologies of the Vertebrate Skeleton, he quotes approvingly the Platonic hypothesis of ἰδέαι, “a sort of models, or moulds in which matter is cast, and which regularly produce the same number and diversity of species.” The vertebrate form in general (see diagram of the Archetypus), or else the form of each kind of vertebrate animal (see p. 172, where this seems implied), Professor Owen conceives to exist as an “idea”--an “archetypal exemplar on which it has pleased the Creator to frame certain of his living creatures.” Whether Professor Owen holds that the typical vertebra also exists as an “idea,” is not so certain. From the title given to his figure of the “ideal typical vertebra,” it would seem that he does; and at p. 40 of his Nature of Limbs, and indeed throughout his general argument, this supposition is implied. But on the last two pages of the Archetype and Homologies, it is distinctly alleged that “the repetition of similar segments in a vertebral column, and of similar elements in a vertebral segment, is analogous to the repetition of similar crystals as the result of polarizing force in the growth of an inorganic body;” it is pointed out that, “as we descend the scale of animal life, the forms of the repeated parts of the skeleton approach more and more to geometrical figures;” and it is inferred that “the Platonic ἰδέα or specific organizing principle or force, would seem to be in antagonism with the general polarizing force, and to subdue and mould it in subserviency to the exigencies of the resulting specific form.” If Professor Owen’s doctrine is to be understood as expressed in these closing paragraphs of his Archetype and Homologies--if he considers that “the ἰδέα” “which produces the diversity of form belonging to living bodies of the same materials,” is met by the “counter-operation” of “the polarizing force pervading all space,” which produces “the similarity of forms, the repetition of parts, the signs of unity of organization,” and which is “subdued” as we ascend “in the scale of being;” then we may pass on with the remark that the hypothesis is too cumbrous and involved to have much vraisemblance. If, on the other hand, Professor Owen holds, as every reader would suppose from the general tenor of his reasonings, that not only does there exist an archetypal or ideal vertebrate skeleton, but that there also exists an archetypal or ideal vertebra; then he carries the Platonic hypothesis much further than Plato does. Plato’s argument, that before any species of object was created it must have existed as an idea of the Creative Intelligence, and that hence all objects of such species must be copies of this original idea, is tenable enough from the anthropomorphic point of view. But while those who, with Plato, think fit to base their theory of creation upon the analogy of a carpenter designing and making a table, must yield assent to Plato’s inference, they are by no means committed to Professor Owen’s expansion of it. To say that before creating a vertebrate animal, God must have had the conception of one, does not involve saying that God gratuitously bound himself to make a vertebrate animal out of segments all moulded after one pattern. As there is no conceivable advantage in this alleged adhesion to a fundamental pattern--as, for the fulfilment of the intended ends, it is not only needless, but often, as Professor Owen argues, less appropriate than some other construction would be (see Nature of Limbs, pp. 39, 40), to suppose the creative processes thus regulated, is not a little startling. Even those whose conceptions are so anthropomorphic as to think they honour the Creator by calling him “the Great Artificer,” will scarcely ascribe to him a proceeding which, in a human artificer, they would consider a not very worthy exercise of ingenuity.

But whichever of these alternatives Professor Owen contends for--whether the typical vertebra is that more or less crystalline figure which osseous matter ever tends to assume in spite of “the ἰδέα or organizing principle,” or whether the typical vertebra is itself an “ἰδέα or organizing principle”--there is alike implied the belief that the typical vertebra has an abstract existence apart from actual vertebræ. It is a form which, in every endo-skeleton, strives to embody itself in matter--a form which is potentially present in each vertebra; which is manifested in each vertebra with more or less clearness; but which, in consequence of antagonizing forces, is nowhere completely realized. Apart from the philosophy of this hypothesis, let us here examine the evidence which is thought to justify it.

* * * * *

And first as to the essential constituents of the “ideal typical vertebra.” Exclusive of “diverging appendages” which it “may also support,” “it consists in its typical completeness of the following elements and parts”:--A centrum round which the rest are arranged in a somewhat radiate manner; above it two neurapophyses--converging as they ascend, and forming with the centrum a trianguloid space containing the neural axis; a neural spine, surmounting the two neurapophyses, and with them completing the neural arch; below the centrum two hæmapophyses and a hæmal spine, forming a hæmal arch similar to the neural arch above, and enclosing the hæmal axis; two pleurapophyses radiating horizontally from the sides of the centrum; and two parapophyses diverging from the centrum below the pleurapophyses. “These,” says Professor Owen, “being usually developed from distinct and independent centres, I have termed ‘autogenous elements.’” The remaining elements, which he classes as “exogenous,” because they “shoot out as continuations from some of the preceding elements,” are the diapophyses diverging from the upper part of the centrum as the parapophyses do below, and the zygapophyses which grow out of the distal ends of the neurapophyses and hæmapophyses.

If, now, these are the constituents of the vertebrate segment “in its typical completeness;” and if the vertebrate skeleton consists of a succession of such segments; we ought to have in these constituents, representatives of all the elements of the vertebrate skeleton--at any rate, all its essential elements. Are we then to conclude that the “diverging appendages,” which Professor Owen regards as rudimental limbs, and from certain of which he considers actual limbs to be developed, are typically less important than some of the above-specified exogenous parts--say the zygapophyses?

That the meaning of this question may be understood, it will be needful briefly to state Professor Owen’s theory of The Nature of Limbs; and such criticisms as we have to make on it must be included in the parenthesis. In the first place, he aims to show that the scapular and pelvic arches, giving insertion to the fore and hind limbs respectively, are displaced and modified hæmal arches, originally belonging in the one case to the occipital vertebra, and in the other case to some trunk-vertebra not specified. In support of this assumption of displacement, carried in some cases to the extent of twenty-seven vertebræ, Professor Owen cites certain acknowledged displacements which occur in the human skeleton to the extent of half a vertebra--a somewhat slender justification. But for proof that such a displacement has taken place in the scapular arch, he chiefly relies on the fact that in fishes, the pectoral fins, which are the homologues of the fore-limbs, are directly articulated to certain bones at the back of the head, which he alleges are parts of the occipital vertebra. This appeal to the class of fishes is avowedly made on the principle that these lowest of the Vertebrata approach closest to archetypal regularity, and may therefore be expected to show the original relations of the bones more nearly. Simply noting the facts that Professor Owen does not give us any transitional forms between the alleged normal position of the scapular arch in fishes, and its extraordinary displacement in the higher Vertebrata; and that he makes no reference to the embryonic phases of the higher Vertebrata, which might be expected to exhibit the progressive displacement; we go on to remark that, in the case of the pelvic arch, he abandons his principle of appealing to the lowest vertebrate forms for proof of the typical structure. In fishes, the rudimentary pelvis, widely removed from the spinal column, shows no signs of having belonged to any vertebra; and here Professor Owen instances the perennibranchiate Batrachia as exhibiting the typical structure: remarking that “mammals, birds, and reptiles show the rule of connexion, and fishes the exception.” Thus in the case of the scapular arch, the evidence afforded by fishes is held of great weight, because of their archetypal regularity; while in the case of the pelvic arch, their evidence is rejected as exceptional. But now, having, as he considers, shown that these bony frames to which the limbs are articulated are modified hæmal arches, Professor Owen points out that the hæmal arches habitually bear certain “diverging appendages;” and he aims to show that the “diverging appendages” of the scapular and pelvic arches respectively, are developed into the fore and hind limbs. There are several indirect ways in which we may test the probability of this conclusion. If these diverging appendages are “rudimental limbs”--“future possible or potential arms, legs, wings, or feet,” we may fairly expect them always to bear to the hæmal arches a relation such as the limbs do. But they by no means do this. “As the vertebræ approach the tail, these appendages are often transferred gradually from the pleurapophysis to the parapophysis, or even to the centrum and neural arch.” (Arch. and Hom., p. 93.) Again, it might naturally be assumed that in the lowest vertebrate forms, where the limbs are but little developed, they would most clearly display their alliance with the appendages, or “rudimental limbs,” by the similarity of their attachments. Instead of this, however, Professor Owen’s drawings show that whereas the appendages are habitually attached to the pleurapophyses, the limbs, in their earliest and lowest phase, alike in fishes and in the Lepidosiren, are articulated to the hæmapophyses. Most anomalous of all, however, is the process of development. When we speak of one thing as being developed out of another, we imply that the parts next to the germ are the first to appear, and the most constant. In the evolution of a tree out of a seed, there come at the outset the stem and the radicle; afterwards the branches and divergent roots; and still later the branchlets and rootlets; the remotest parts being the latest and most inconstant. If, then, a limb is developed out of a “diverging appendage” of the hæmal arch, the earliest and most constant bones should be the humerus and femur; next in order of time and constancy should come the coupled bones based on these; while the terminal groups of bones should be the last to make their appearance, and the most liable to be absent. Yet, as Professor Owen himself shows, the actual mode of development is the very reverse of this. At p. 16 of the Archetype and Homologies, he says:--

“The earlier stages in the development of all locomotive extremities are permanently retained or represented in the paired fins of fishes. First the essential part of the member, the hand or foot, appears: then the fore-arm or leg, both much shortened, flattened, and expanded, as in all fins and all embryonic rudiments of limbs: finally come the humeral and femoral segments; but this stage I have not found attained in any fish.”

That is to say, alike in ascending through the Vertebrata, generally, and in tracing up the successive phases of a mammalian embryo, the last-developed and least constant division of the limb, is that basic one by which it articulates with the hæmal arch. It seems to us that, so far from proving his hypothesis, Professor Owen’s own facts tend to show that limbs do not belong to the vertebræ at all: that they make their first appearance peripherally; that their development is centripetal; and that they become fixed to such parts of the vertebrate axis as the requirements of the case determine.

But now, ending here this digressive exposition and criticism, and granting the position that limbs “are developments of costal appendages,” let us return to the question above put--Why are not these appendages included as elements of the “ideal typical vertebra?” It cannot be because of their comparative inconstancy; for judging from the illustrative figures, they seem to be as constant as the hæmal spine, which is one of the so-called autogenous elements: in the diagram of the Archetypus, the appendage is represented as attached to every vertebrate segment of the head and trunk, which the hæmal spine is not. It cannot be from their comparative unimportance; seeing that as potential limbs they are essential parts of nearly all the Vertebrata--much more obviously so than the diapophyses are. If, as Professor Owen argues, “the divine mind which planned the archetype also foreknew all its modifications;” and if, among these modifications, the development of limbs out of diverging appendages was one intended to characterize all the higher Vertebrata; then, surely, these diverging appendages must have been parts of the “ideal typical vertebra.” Or, if the “ideal typical vertebra” is to be understood as a crystalline form in antagonism with the organizing principle; then why should not the appendages be included among its various offshoots? We do not ask this question because of its intrinsic importance. We ask it for the purpose of ascertaining Professor Owen’s method of determining what are true vertebral constituents. He presents us with a diagram of the typical vertebra, in which are included certain bones, and from which are excluded certain others. If relative constancy is the criterion, then there arises the question--What degree of constancy entitles a bone to be included? If relative importance is the criterion, there comes not only the question--What degree of importance suffices? but the further question--How is importance to be measured? If neither of these is the criterion, then what is it? And if there is no criterion, does it not follow that the selection is arbitrary?

* * * * *

This question serves to introduce a much wider one:--Has the “ideal typical vertebra” any essential constituents at all? It might naturally be supposed that though some bones are so rarely developed as not to seem worth including, and though some that are included are very apt to be absent, yet that certain others are invariable: forming, as it were, the basis of the ideal type. Let us see whether the facts bear out this supposition. In his “summary of modifications of corporal vertebræ” (p. 96), Professor Owen says--“The hæmal spine is much less constant as to its existence, and is subject to a much greater range of variety, when present, than its vertical homotype above, which completes the neural arch.” Again he says--“The hæmapophyses, as osseous elements of a vertebra, are less constant than the pleurapophyses.” And again--“The pleurapophyses are less constant elements than the neurapophyses.” And again--“Amongst air-breathing vertebrates the pleurapophyses of the trunk segments are present only in those species in which the septum of the heart’s ventricle is complete and imperforate, and here they are exogenous and confined to the cervical and anterior thoracic vertebræ.” And once more, both the neurapophyses and the neural spine “are absent under both histological conditions, at the end of the tail in most air-breathing vertebrates, where the segments are reduced to their central elements.” That is to say, of all the peripheral elements of the “ideal typical vertebra,” there is not one which is always present. It will be expected, however, that at any rate the centrum is constant: the bone which “forms the axis of the vertebral column, and commonly the central bond of union of the peripheral elements of the vertebrate (p. 97), is of course an invariable element. No: not even this is essential.

“The centrums do not pass beyond the primitive stage of the notochord (undivided column) in the existing lepidosiren, and they retained the like rudimental state in every fish whose remains have been found in strata earlier than the permian æra in Geology, though the number of vertebræ is frequently indicated in Devonian and Silurian ichthyolites by the fossilized neur-and hæmapophyses and their spines” (p. 96).

Indeed, Professor Owen himself remarks that “the neurapophyses are more constant as osseous or cartilaginous elements of the vertebræ than the centrums” (p. 97). Thus, then, it appears that the several elements included in the “ideal typical vertebra” have various degrees of constancy, and that no one of them is essential. There is no one part of a vertebra which invariably answers to its exemplar in the pattern-group. How does this fact consist with the hypothesis? If the Creator saw fit to make the vertebrate skeleton out of a series of segments, all formed on essentially the same model--if, for the maintenance of the type, one of these bony segments is in many cases formed out of a coalesced group of pieces, where, as Professor Owen argues, a single piece would have served as well or better; then we ought to find this typical repetition of parts uniformly manifested. Without any change of shape, it would obviously have been quite possible for every actual vertebra to have contained all the parts of the ideal one--rudimentally where they were not wanted. Even one of the terminal bones of a mammal’s tail might have been formed out of the nine autogenous pieces, united by suture but admitting of identification. As, however, there is no such uniform typical repetition of parts, it seems to us that to account for the typical repetition which does occur, by supposing the Creator to have fixed on a pattern-vertebra, is to ascribe to him the inconsistency of forming a plan and then abandoning it.

If, on the other hand, Professor Owen means that the “ideal typical vertebra” is a crystalline form in antagonism with “the idea or organizing principle;” then we might fairly expect to find it most clearly displaying its crystalline character, and its full complement of parts, in those places where the organizing principle may be presumed to have “subdued” it to the smallest extent. Yet in the Vertebrata generally, and even in Professor Owen’s Archetypus, the vertebræ of the tail, which must be considered as, if anything, less under the influence of the organizing principle than those of the trunk, do not manifest the ideal form more completely. On the contrary, as we approach the end of the tail, the successive segments not only lose their remaining typical elements, but become as uncrystalline-looking as can be conceived.

* * * * *

Supposing, however, that the assumption of suppressed or undeveloped elements be granted--supposing it to be consistent with the hypothesis of an “ideal typical vertebra,” that the constituent parts may severally be absent in greater or less number, sometimes leaving only a single bone to represent them all; may it not be that such parts as are present, show their respective typical natures by some constant character: say their mode of ossification?

To this question some parts of the Archetype and Homologies seem to reply, “Yes;” while others clearly answer, “No.” Criticising the opinions of Geoffrey St. Hilaire and Cuvier, who agreed in thinking that ossification from a separate centre was the test of a separate bone, and that thus there were as many elementary bones in the skeleton as there were centres of ossification, Professor Owen points out that, according to this test, the human femur, which is ossified from four centres, must be regarded as four bones; while the femur in birds and reptiles, which is ossified from a single centre, must be regarded as a single bone. Yet, on the other hand, he attaches weight to the fact that the skull of the human fœtus presents “the same ossific centres” as do those of the embryo kangaroo and the young bird. (Nature of Limbs, p. 40.) And at p. 104 of the Homologies, after giving a number of instances, he says--

“These and the like correspondences between the points of ossification of the human fœtal skeleton, and the separate bones of the adult skeletons of inferior animals, are pregnant with interest, and rank among the most striking illustrations of unity of plan in the vertebrate organization.”

It is true that on the following page he seeks to explain this seeming contradiction by distinguishing

“between those centres of ossification that have homological relations, and those that have teleological ones--i.e., between the separate points of ossification of a human bone which typify vertebral elements, often permanently distinct bones in the lower animals; and the separate points which, without such signification, facilitate the progress of osteogeny, and have for their obvious final cause the well-being of the growing animal.”

But if there are thus centres of ossification which have homological meanings, and others which have not, there arises the question--How are they always to be distinguished? Evidently independent ossification ceases to be a homological test, if there are independent ossifications that have nothing to do with the homologies. And this becomes the more evident when we learn that there are cases where neither a homological nor a teleological meaning can be given. Among various modes of ossification of the centrum, Professor Owen points out that “the body of the human atlas is sometimes ossified from two, rarely from three, distinct centres placed side by side” (p. 89); while at p. 87 he says:--“In osseous fishes I find that the centrum is usually ossified from six points.” It is clear that this mode of ossification has here no homological signification; and it would be difficult to give any teleological reason why the small centrum of a fish should have more centres of ossification than the large centrum of a mammal. The truth is, that as a criterion of the identity or individuality of a bone, mode of ossification is quite untrustworthy. Though, in his “ideal typical vertebra,” Professor Owen delineates and classifies as separate “autogenous” elements, those parts which are “usually developed from distinct and independent centres;” and though by doing so he erects this characteristic into some sort of criterion; yet his own facts show it to be no criterion. The parapophyses are classed among the autogenous elements; yet they are autogenous in fishes alone, and in these only in the trunk vertebræ, while in all air-breathing vertebrates they are, when present at all, exogenous. The neurapophyses, again, “lose their primitive individuality by various kinds and degrees of confluence:” in the tails of the higher Vertebrata they, in common with the neural spine, become exogenous. Nay, even the centrum may lose its autogenous character. Describing how, in some batrachians, “the ossification of the centrum is completed by an extension of bone from the bases of the neurapophyses, which effects also the coalescence of these with the centrum,” Professor Owen adds:--“In Pelobates fuscus and Pelobates cultripes, Müller found the entire centrum ossified from this source, without any independent points of ossification” (p. 88). That is to say, the centrum is in these cases an exogenous process of the neurapophyses. We see, then, that these so-called typical elements of vertebræ have no constant developmental character by which they can be identified. Not only are they undistinguishable by any specific test from other bones not included as vertebral elements; not only do they fail to show their typical characters by their constant presence; but, when present, they exhibit no persistent marks of individuality. The central element may be ossified from six, four, three, or two points; or it may have no separate point of ossification at all: and similarly with various of the peripheral elements. The whole group of bones forming the “ideal typical vertebra” may severally have their one or more ossific centres; or they may, as in a mammal’s tail, lose their individualities in a single bone ossified from one or two points.

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Another fact which seems very difficult to reconcile with the hypothesis of an “ideal typical vertebra,” is the not infrequent presence of some of the typical elements in duplicate. Not only, as we have seen, may they severally be absent, but they may severally be present in greater number than they should be. When we see, in the ideal diagram, one centrum, two neurapophyses, two pleurapophyses, two hæmapophyses, one neural spine, and one hæmal spine, we naturally expect to find them always bearing to each other these numerical relations. Though we may not be greatly surprised by the absence of some of them, we are hardly prepared to find others multiplied. Yet such cases are common. Thus the neural spine “is double in the anterior vertebræ of some fishes” (p. 98). Again, in the abdominal region of extinct saurians, and in crocodiles, “the freely-suspended hæmapophyses are compounded of two or more overlapping bony pieces” (p. 100). Yet again, at p. 99, we read--“I have observed some of the expanded pleurapophyses in the great Testudo elephantopus ossified from two centres, and the resulting divisions continuing distinct, but united by suture.” Once more “the neurapophyses, which do not advance beyond the cartilaginous stage in the sturgeon, consist in that fish of two distinct pieces of cartilage; and the anterior pleurapophyses also consist of two or more cartilages, set end on end” (p. 91). And elsewhere referring to this structure, he says:--

“Vegetative repetition of perivertebral parts not only manifests itself in the composite neurapophyses and pleurapophyses, but in a small accessory (interneural) cartilage, at the fore and back part of the base of the neurapophysis; and by a similar (interhæmal) one at the fore and back part of most of the parapophyses” (p. 87).

Thus the neural and hæmal spines, the neurapophyses, the pleurapophyses, the hæmapophyses, may severally consist of two or more pieces. This is not all: the like is true even of the centrums.

“In Heptanchus (Squalus cinereus) the vertebral centres are feebly and vegetatively marked out by numerous slender rings of hard cartilage in the notochordal capsule, the number of vertebræ being more definitely indicated by the neurapophyses and parapophyses.... In the piked dog-fish (Acanthias) and the spotted dog-fish (Scyllium) the vertebral centres coincide in number with the neural arches” (p. 87).

Is it not strange that the pattern-vertebra should be so little adhered to, that each of its single typical pieces may be transformed into two or three?

But there are still more startling departures from the alleged type. The numerical relations of the elements vary not only in this way, but in the opposite way. A given part may be present not only in greater number than it should be, but also in less. In the tails of homocercal fishes, the centrums “are rendered by centripetal shortening and bony confluence fewer in number than the persistent, neural, and hæmal arches of that part”--that is, there is only a fraction of a centrum to each vertebra. Nay, even this is not the most heteroclite structure. Paradoxical as it may seem, there are cases in which the same vertebral element is, considered under different aspects, at once in excess and defect. Speaking of the hæmal spine, Professor Owen says:--

“The horizontal extension of this vertebral element is sometimes accompanied by a median division, or in other words, it is ossified from two lateral centres; this is seen in the development of parts of the human sternum; the same vegetative character is constant in the broader thoracic hæmal spines of birds; though, sometimes, as e.g., in the struthionidæ, ossification extends from the same lateral centre lengthwise--i.e., forwards and backwards, calcifying the connate cartilaginous homologues of halves of four or five hæmal spines, before these finally coalesce with their fellows at the median line” (p. 101).

So that the sternum of the ostrich, which according to the hypothesis, should, in its cartilaginous stage, have consisted of four or five transverse pieces, answering to the vertebral segments, and should have been ossified from four or five centres, one to each cartilaginous piece, shows not a trace of this structure; but instead, consists of two longitudinal pieces of cartilage, each ossified from one centre, and finally coalescing on the median line. These four or five hæmal spines have at the same time doubled their individualities transversely, and entirely lost them longitudinally!

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There still remains to be considered the test of relative position. It might be held that, spite of all the foregoing anomalies, if the typical parts of the vertebræ always stood towards each other in the same relations--always preserved the same connexions, something like a case would be made out. Doubtless, relative position is an important point; and it is one on which Professor Owen manifestly places great dependence. In his discussion of “moot cases of special homology,” it is the general test to which he appeals. The typical natures of the alisphenoid, the mastoid, the orbito-sphenoid, the prefrontal, the malar, the squamosal, &c. he determines almost wholly by reference to the adjacent nerve-perforations and the articulations with neighbouring bones (see pp. 19 to 72): the general form of the argument being--This bone is to be classed as such or such, because it is connected thus and thus with these others, which are so and so. Moreover, by putting forth an “ideal typical vertebra,” consisting of a number of elements standing towards each other in certain definite arrangement, this persistency of relative position is manifestly alleged. The essential attribute of this group of bones, considered as a typical group, is the constancy in the connexions of its parts: change the connexions, and the type is changed. But the constancy of relative position thus tacitly asserted, and appealed to as a conclusive test in “moot cases of special homology,” is clearly negatived by Professor Owen’s own facts. For instance, in the “ideal typical vertebra,” the hæmal arch is represented as formed by the two hæmapophyses and the hæmal spine; but at p. 91 we are told that

“The contracted hæmal arch in the caudal region of the body may be formed by different elements of the typical vertebra: e.g., by the parapophyses (fishes generally); by the pleurapophyses (lepidosiren); by both parapophyses and pleurapophyses (Sudis, Lepidosteus), and by hæmapophyses, shortened and directly articulated with the centrums (reptiles and mammals).”

And further, in the thorax of reptiles, birds, and mammals, “the hæmapophyses are removed from the centrum, and are articulated to the distal ends of the pleurapophyses; the bony hoop being completed by the intercalation of the hæmal spine” (p. 82). So that there are five different ways in which the hæmal arch may be formed--four modes of attachment of the parts different from that shown in the typical diagram! Nor is this all. The pleurapophyses “may be quite detached from their proper segment, and suspended to the hæmal arch of another vertebra;” as we have already seen, the entire hæmal arch may be detached and removed to a distance, sometimes reaching the length of twenty-seven vertebræ; and, even more remarkable, the ventral fins of some fishes, which theoretically belong to the pelvic arch, are so much advanced forward as to be articulated to the scapular arch--“the ischium elongating to join the coracoid.” With these admissions it seems to us that relative position and connexions cannot be appealed to as tests of homology, nor as evidence of any original type of vertebra.

In no class of facts, then, do we find a good foundation for the hypothesis of an “ideal typical vertebra.” There is no one conceivable attribute of this archetypal form which is habitually realised by actual vertebræ. The alleged group of true vertebral elements is not distinguished in any specified way from bones not included in it. Its members have various degrees of inconstancy; are rarely all present together; and no one of them is essential. They are severally developed in no uniform way: each of them may arise either out of a separate piece of cartilage, or out of a piece continuous with that of some other element; and each may be ossified from many independent points, from one, or from none. Not only may their respective individualities be lost by absence, or by confluence with others; but they may be doubled, or tripled, or halved, or may be multiplied in one direction and lost in another. The entire group of typical elements may coalesce into one simple bone representing the whole vertebra; and even, as in the terminal piece of a bird’s tail, half-a-dozen vertebræ, with all their many elements, may become entirely lost in a single mass. Lastly, the respective elements, when present, have no fixity of relative position: sundry of them are found articulated to various others than those with which they are typically connected; they are frequently displaced and attached to neighbouring vertebræ; and they are even removed to quite remote parts of the skeleton. It seems to us that if this want of congruity with the facts does not disprove the hypothesis, no such hypothesis admits of disproof.

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Unsatisfactory as is the evidence in the case of the trunk and tail vertebræ, to which we have hitherto confined ourselves, it is far worse in the case of the alleged cranial vertebræ. The mere fact that those who have contended for the vertebrate structure of the skull, have differed so astonishingly in their special interpretations of it, is enough to warrant great doubt as to the general truth of their theory. From Professor Owen’s history of the doctrine of general homology, we gather that Duméril wrote upon “la tête considérée comme une vertèbre;” that Kielmeyer, “instead of calling the skull a vertebra, said each vertebra might be called a skull;” that Oken recognized in the skull three vertebræ and a rudiment; that Professor Owen himself makes out four vertebræ; that Goethe’s idea, adopted and developed by Carus, was, that the skull is composed of six vertebræ; and that Geoffrey St. Hilaire divided it into seven. Does not the fact that different comparative anatomists have arranged the same group of bones into one, three, four, six, and seven vertebral segments, show that the mode of determination is arbitrary, and the conclusions arrived at fanciful? May we not properly entertain great doubts as to any one scheme being more valid than the others? And if out of these conflicting schemes we are asked to accept one, ought we not to accept it only on the production of some thoroughly conclusive proof--some rigorous test showing irrefragably that the others must be wrong and this alone right? Evidently where such contradictory opinions have been formed by so many competent judges, we ought, before deciding in favour of one of them, to have a clearness of demonstration much exceeding that required in any ordinary case. Let us see whether Professor Owen supplies us with any such clearness of demonstration.

To bring the first or occipital segment of the skull into correspondence with the “ideal typical vertebra,” Professor Owen argues, in the case of the fish, that the parapophyses are displaced, and wedged between the neurapophyses and the neural spine--removed from the hæmal arch and built into the upper part of the neural arch. Further, he considers that the pleurapophyses are teleologically compound. And then, in all the higher vertebrata, he alleges that the hæmal arch is separated from its centrum, taken to a distance, and transformed into the scapular arch. Add to which, he says that in mammals the displaced parapophyses are mere processes of the neurapophyses (p. 133): these vertebral elements, typically belonging to the lower part of the centrum, and in nearly all cases confluent with it, are not only removed to the far ends of elements placed above the centrum, but have become exogenous parts of them!

Conformity of the second or parietal segment of the cranium with the pattern-vertebra, is produced thus:--The petrosals are excluded as being partially-ossified sense-capsules, not forming parts of the true vertebral system, but belonging to the “splanchno-skeleton.” A centrum is artificially obtained by sawing in two the bone which serves in common as centrum to this and the preceding segment; and this though it is admitted that in fishes, where their individualities ought to be best seen, these two hypothetical centrums are not simply coalescent, but connate. Next, a similar arbitrary bisection is made of certain elements of the hæmal arches. And then, “the principle of vegetative repetition is still more manifest in this arch than in the occipital one:” each pleurapophysis is double; each hæmapophysis is double; and the hæmal spine consists of six pieces!

The interpretation of the third and fourth segments being of the same general character, need not be detailed. The only point calling for remark being, that in addition to the above various modes of getting over anomalies, we find certain bones referred to the dermo-skeleton.

Now it seems to us, that even supposing no antagonist interpretations had been given, an hypothesis reconcilable with the facts only by the aid of so many questionable devices, could not be considered satisfactory; and that when, as in this case, various comparative anatomists have contended for other interpretations, the character of this one is certainly not of a kind to warrant the rejection of the others in its favour; but rather of a kind to make us doubt the possibility of all such interpretations. The question which naturally arises is, whether by proceeding after this fashion, groups of bones might not be arranged into endless typical forms. If, when a given element was not in its place, we were at liberty to consider it as suppressed, or connate with some neighbouring element, or removed to some more or less distant position;--if, on finding a bone in excess, we might consider it, now as part of the dermo-skeleton, now as part of the splanchno-skeleton, now as transplanted from its typical position, now as resulting from vegetative repetition, and now as a bone teleologically compound (for these last two are intrinsically different, though often used by Professor Owen as equivalents);--if, in other cases, a bone might be regarded as spurious (p. 91), or again as having usurped the place of another;--if, we say, these various liberties were allowed us, we should not despair of reconciling the facts with various diagrammatic types besides that adopted by Professor Owen.

When, in 1851, we attended a course of Professor Owen’s lectures on Comparative Osteology, beginning though we did in the attitude of discipleship, our scepticism grew as we listened, and reached its climax when we came to the skull; the reduction of which to the vertebrate structure, reminded us very much of the interpretation of prophecy. The delivery, at the Royal Society, of the Croonian Lecture for 1858, in which Professor Huxley, confirming the statements of several German anatomists, has shown that the facts of embryology do not countenance Professor Owen’s views respecting the formation of the cranium, has induced us to reconsider the vertebral theory as a whole. Closer examination of Professor Owen’s doctrines, as set forth in his works, has certainly not removed the scepticism generated years ago by his lectures. On the contrary, that scepticism has deepened into disbelief. And we venture to think that the evidence above cited shows this disbelief to be warranted.

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There remains the question--What general views are we to take respecting the vertebrate structure? If the hypothesis of an “ideal typical vertebra” is not justified by the facts, how are we to understand that degree of similarity which vertebræ display?

We believe the explanation is not far to seek. All that our space will here allow, is a brief indication of what seems to us the natural view of the matter.

Professor Owen, in common with other comparative anatomists, regards the divergences of individual vertebræ from the average form, as due to adaptive modifications. If here one vertebral element is largely developed, while elsewhere it is small--if now the form, now the position, now the degree of coalescence, of a given part varies; it is that the local requirements have involved this change. The entire teaching of comparative osteology implies that differences in the conditions of the respective vertebræ necessitate differences in their structures.

Now, it seems to us that the first step towards a right conception of the phenomena, is to recognize this general law in its converse application. If vertebræ are unlike in proportion to the unlikeness of their circumstances, then, by implication, they will be like in proportion to the likeness of their circumstances. While successive segments of the same skeleton, and of different skeletons, are all in some respects more or less differently acted on by incident forces, and are therefore required to be more or less different; they are all, in other respects, similarly acted on by incident forces, and are therefore required to be more or less similar. It is impossible to deny that if differences in the mechanical functions of the vertebræ involve differences in their forms; then, community in their mechanical functions, must involve community in their forms. And as we know that throughout the Vertebrata generally, and in each vertebrate animal, the vertebræ, amid all their varying circumstances, have a certain community of function, it follows necessarily that they will have a certain general resemblance--there will recur that average shape which has suggested the notion of a pattern-vertebra.

A glance at the facts at once shows their harmony with this conclusion. In an eel or a snake, where the bodily actions are such as to involve great homogeneity in the mechanical conditions of the vertebræ, the series of them is comparatively homogeneous. On the contrary, in a mammal or a bird, where there is considerable heterogeneity in their circumstances, their similarity is no longer so great. And if, instead of comparing the vertebral columns of different animals, we compare the successive vertebræ of any one animal, we recognize the same law. In the segments of an individual spine, where is there the greatest divergence from the common mechanical conditions? and where may we therefore expect to find the widest departure from the average form? Obviously at the two extremities. And accordingly it is at the two extremities that the ordinary structure is lost.

Still clearer becomes the truth of this view, when we consider the genesis of the vertebral column as displayed throughout the ascending grades of the Vertebrata. In its first embryonic stage, the spine is an undivided column of flexible substance. In the early fishes, while some of the peripheral elements of the vertebræ were marked out, the central axis was still a continuous unossified cord. And thus we have good reason for thinking that in the primitive vertebrate animal, as in the existing Amphioxus, the notochord was persistent. The production of a higher, more powerful, more active creature of the same type, by whatever method it is conceived to have taken place, involved a change in the notochordal structure. Greater muscular endowments presupposed a firmer internal fulcrum --a less yielding central axis. On the other hand, for the central axis to have become firmer while remaining continuous, would have entailed a stiffness incompatible with the creature’s movements. Hence, increasing density of the central axis necessarily went hand in hand with its segmentation: for strength, ossification was required; for flexibility, division into parts. The production of vertebræ resulting thus, there obviously would arise among them a general likeness, due to the similarity in their mechanical conditions, and more especially the muscular forces bearing on them. And then observe, lastly, that where, as in the head, the terminal position and the less space for development of muscles, entailed smaller lateral bendings, the segmentation would naturally be less decided, less regular, and would be lost as we approached the front of the head.

But, it may be replied, this hypothesis does not explain all the facts. It does not tell us why a bone whose function in a given animal requires it to be solid, is formed not of a single piece, but by the coalescence of several pieces, which in other creatures are separate; it does not account for the frequent manifestations of unity of plan in defiance of teleological requirements. This is quite true. But it is not true, as Professor Owen argues respecting such cases, that “if the principle of special adaptation fails to explain them, and we reject the idea that these correspondences are manifestations of some archetypal exemplar, on which it has pleased the Creator to frame certain of his living creatures, there remains only the alternative that the organic atoms have concurred fortuitously to produce such harmony.” This is not the only alternative: there is another, which Professor Owen has overlooked. It is a perfectly tenable supposition that all higher vertebrate forms have arisen by the superposing of adaptations upon adaptations. Either of the two antagonist cosmogonies consists with this supposition. If, on the one hand, we conceive species to have resulted from acts of special creation; then it is quite a fair assumption that to produce a higher vertebrate animal, the Creator did not begin afresh, but took a lower vertebrate animal, and so far modified its pre-existing parts as to fit them for the new requirements; in which case the original structure would show itself through the superposed modifications. If, on the other hand, we conceive species to have resulted by gradual differentiations under the influence of changed conditions; then, it would manifestly follow that the higher, heterogeneous forms, would bear traces of the lower and more homogeneous forms from which they were evolved.

Thus, besides finding that the hypothesis of an “ideal typical vertebra” is irreconcilable with the facts, we find that the facts are interpretable without gratuitous assumptions. The average community of form which vertebræ display, is explicable as resulting from natural causes. And those typical similarities which are traceable under adaptive modifications, must obviously exist if, throughout creation in general, there has gone on that continuous superposing of modifications upon modifications which goes on in every unfolding organism.

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