But the question now arises, whether both Darwinism and Lamarckism must not be replaced, or at least reduced to the level of accessory theories and factors, by another theory of evolution which was in the field before Darwin, and which since his time has been advanced anew, especially by Nageli, and has now many adherents who support it in whole or in part.

This view affects the very foundations of the Darwinian doctrine. The theory of "indefinite" variation, bringing about easy transitions and affecting every part of the organism separately, which is the necessary correlate of the "struggle for existence," is rejected altogether.

Evolution takes place only along a few definite lines, predetermined through the internal organisation and the laws of growth. It is wholly indifferent to "utility," and brings forth only what it must according to its own inner laws, not seldom even the monstrous. According to this view, new species arise, not in easy transition, but with a visible leap, by a considerable and far-reaching displacement of the organic equilibrium.

What Darwin calls the correlation of parts, and in no way denies, is here maintained in strong opposition to his doctrine of the isolated variation of individual parts; every member or character of the organism depends upon others, and variation of one affects many, and in some way all of the rest.

This theory is for the most part intended by its champions to be purely naturalistic. But every one of its points yields support to teleological considerations, most obviously so the concrete instances of correlation.

If any one were to attempt to make a theory of evolution from a decidedly teleological standpoint, he would probably construct one very similar to the one we are now considering.

It is noteworthy that it has generally been the botanists who have especially supported these views of saltatory evolution in a definite direction and according to internal law, who have therefore tended to react most strongly from Darwinism. We find examples in Nageli's large and comprehensive work, "Mechanisch-physikalische Theorie der Abstammungslehre"; and, before him, in Wigand's "Darwinismus und die Naturforschung Newton's und Cuvier's"; in von Kolliker's "Heterogenesis"; in von Baer's "Endeavour after an End"; in the chapter added by the translator, Bronn, to the first German edition of the "Origin of Species,"

where he urges weighty objections against the theory of selection, and refers to the "innate impulse to development, persistently varying in a definite direction"; in Askenasy's oft-quoted "Beitrage zur Kritik der Darwinschen Lehre," also referring to "variation in a definite direction,"

for instance, in flowers; in Delpino's views, and in the works of many other older writers. But we must leave all these out of account here, since we are concerned only with the present state of the question.

De Vries's Mutation-theory.

The work that has probably excited most interest in this connection is De Vries' "Die Mutationstheorie: Versuche und Beobachtungen uber die Entstehung von Arten im Pflanzenleben."(46) In a short preliminary paper he had previously given some account of his leading experiments on a species of evening primrose (_nothera lamarckiana_), and the outlines of his theory. In the work itself he extends this, adding much concrete material, and comparing his views in detail with other theories. Darwin, he says, had already distinguished between variability and mutability; the former manifesting itself in gradual and isolated changes, the latter in saltatory changes on a larger scale. The mistake made by Wallace and by the later Darwinians has been that they regarded this latter form ("single variation") as unimportant and not affecting evolution, and the former as the real method of evolutionary process. That fluctuating individual variations do occur De Vries admits, but only within narrow limits, never overstepping the type of the species. Here De Vries utilises the recent statistical investigations into the phenomena of individual variation and their laws, as formulated chiefly by Quetelet and Bateson, which were unknown to Darwin and the earlier Darwinians. The actual transition from "species to species" is made suddenly, by mutation, not through variation.

And the state of equilibrium thus reached is such a relatively stable one that individual variations can only take place within its limits, but can in no way disturb it.

De Vries marshals a series of facts which present insurmountable difficulties to the Darwinian theory, but afford corroboration of the Mutation theory. In particular, he brings forward, from his years of experiment and horticultural observation, comprehensive evidence of the mutational origin of new species from old ones by leaps, and this not in long-past geological times, but in the course of a human life and before our very eyes. The main importance of the book lies in the record of these experiments and observations, rather than in the theory as such, for the way had been paved for it by other workers.

In contrast to Darwinism, De Vries states the case for "Halmatogenesis"

(saltatory evolution) and "Heterogenesis" (the production of forms unlike the parents), taking his examples from the plant world, but his att.i.tude to Darwinism is conciliatory throughout. Eimer, on the other hand, is sharply antagonistic, especially to Weismann; he takes his proofs from the animal kingdom, and in the second volume of his large work already mentioned, which deals with the "orthogenesis of b.u.t.terflies," he attempts to set against the Darwinism "chance theory," a proof of "definitely directed evolution," and therefore of the "insufficiency of natural selection in the formation of species."

Eimer's Orthogenesis.

Organisation is due to internal causes. Structural characters crystallise out, as it were. "Orthogenesis," or the definitely determined tendency of evolution to advance in a few directions, is a law for the whole of the animate world. In active response to the stimuli and influences of the environment the organism expresses itself in "organic growth" without any relation to utility. b.u.t.terflies in particular, and especially their markings and coloration, are taken as ill.u.s.trations. In the Darwinian theory of "mimicry" these played a brilliant part. The great resemblance to leaves, to dried twigs, or to well-protected species which are secure from enemies, was regarded as the most convincing proof of the operation of natural selection. But Eimer shows that markings, striping, spots, the development of pattern, and the alleged or real resemblances to leaves, are really subject to definite laws of growth, in obedience to which they gradually appear, developing according to their own internal laws, varying and progressing altogether by internal necessity, and without any reference to advantage or disadvantage, In a.s.sociation with this orthogenesis, Eimer recognises halmatogenesis, correlation and "genepistasis" (coming to a standstill at a fixed and definite stage), and these seem to him to make the Darwinian theory utterly impossible. The text and the ill.u.s.trations of the book show how, in the sequence of evolution (according to Eimer's laws of transformation), the groupings of stripes, bands, and eye-spots must have appeared on the b.u.t.terfly's wing, how convex or concave curvings of the contour must have come about at certain points, so that the form of a "leaf" and the lines of its venation resulted, how the eye-spots must have been moulded and shunted, so that they produced the effect of rust or other spots on withered leaves.

Particular interest attaches to the detailed arguments against the idea that the b.u.t.terfly must receive some advantage from its "mimicry." Even the Darwinians have to admit that in a whole series of cases the advantage is not obvious. They talk with some embarra.s.sment of "pseudomimicry." Some b.u.t.terflies that are supposed to be protected have the protective markings on the underside, so that these are actually hidden when the insects are flying from pursuing birds. Many of the leaf-like b.u.t.terflies are not wood-b.u.t.terflies at all, but meadow species,(47) and so Eimer's arguments continue.

A specially energetic fellow-worker on Eimer's line is W. Haacke, a zoologist of Jena, author of "Gestaltung und Vererbung," and "Die Schopfung des Menschen und seiner Ideale."(48) In the first of these works Haacke combats, energetically and with much detail, Weismann's "preformation theory," and defends "epigenesis," for which he endeavours to construct graphic diagrams, his aim being to make a foundation for the inheritance of acquired characters, definitely directed evolution, saltatory, symmetrical, and correlated variation.

The principles of the new school are very widespread to-day, but we cannot here follow their development in the works of individual investigators, such as Reinke, R. Hertwig, O. Hertwig, Wiesner, Hamann, Dreyer, Wolff, Goette, Ka.s.sowitz, v. Wettstein, Korschinsky, and others.(49)

The Spontaneous Activity of the Organism.

What is particularly luminous in all the theories that express the most recent anti-Darwinian tendency is that they tend to bring into prominence the mysterious powers of living organisms, by means of which, instead of pa.s.sively waiting for natural selection and the continual acc.u.mulation of unceasing variations, they are able spontaneously and of themselves to bring forth what is necessary for self-maintenance, often what is new and different, of course not unlimitedly, but with considerable freedom and often with a surprising range of possibilities. It is, perhaps, partly the fault of the one-sidedness of strict Darwinism that this consideration has been so slowly brought into prominence and subjected to investigation and experiment. It is bound up with the capacity that all forms of life have of reacting spontaneously to "stimuli" and, to a certain extent, of helping themselves if the conditions of existence be unfavourable. They are able, for instance, to produce protective adaptations against cold or heat, to "regenerate" lost parts, often to replace entire organs that have been lost, and, under certain circ.u.mstances, to produce new organs altogether. If all this be true, it seems almost like caprice to follow only the roundabout theory of the struggle for existence, and not to take account of these spontaneous capacities of the living organism directly and before all other factors in the attempt to explain evolution. There is no end to the ill.u.s.trations that are being adduced, that must force investigation to pa.s.s from merely superficial considerations of the struggle for existence type to the deeper and more real problems themselves.

An effectively modified and adapted type of Alpine flora has not been evolved by a laborious process of selection lasting for many thousand years; the organism may quickly and immediately produce the new characters by its own reaction. Crustaceans gradually transferred from a salt-water to a fresh-water habitat, or conversely, produce in a few generations the type of a new "species" with correlated variations (Schmankewitsch). Birds weaned by careful experiment from a diet of seeds to one of flesh, or conversely, produce changes of effective correlation and adaptation in the characters of their alimentary system. Plants that have been deprived of their normal organs for absorbing water and prevented from growing new ones produce entirely new and effective "hydatodes."(50)

It is instructive to notice that Darwinism seems likely to be robbed of its stock ill.u.s.tration, namely, "protective coloration." By its own internal power of reaction, and sometimes within one generation, and even in the lifetime of an individual, an organism may a.s.sume the colour of the substratum beneath it (soles, gra.s.shoppers), of its surroundings (Eimer's tree frogs), the colour and spottiness of the granite rock on which it hangs, the colour of the leaves and twigs among which it lives (Poulton's b.u.t.terfly pupae), and even that of the brightly coloured sheets of paper amidst which it is kept imprisoned. Certain spiders a.s.sume a white, pink, or greenish "protective coloration" corresponding to the tinted blossom of the plants which they frequent, and so on.(51) Eimer alleged that direct psychical factors co-operated in bringing about these changes. In any case, all this carries us far beyond the domain of mere naturalistic factors into the mystery of life itself. Even what is called the "influence of the external world," and the "active acquirement of new characters," have their basis and the reason of their possibility in this domain. And the whole domain is saturated through and through with "teleology."

A recognition of the impressive secret of the organism led Gustav Wolff to become a very p.r.o.nounced critic of Darwinism, especially in the form of Weismannism. As far back as 1896, in a lecture "On the present position of Darwinism," in which he dealt only with Weismann, he criticised and a.n.a.lysed that author's last attempt to uphold Darwinism by the construction of his theory of "germinal selection." He concluded with the wish:

"That a spirit of earnestness would once more enter into biological investigation, which would no longer attempt to find in nature just what it wanted to find, but would be ready to follow truth at all costs, and to approach the riddle of life with an open mind."

His "Beitrage zur Kritik der Darwinischen Lehre," which appeared first as papers in the "Biologisches Centralblatt," did not see the light in book form until 1898. The doctrine of selection was regarded as so una.s.sailable that no publisher would take the risk of the book. Its appearance is a sure indication of the general modification of opinions that had taken place in the interval. The first and second essays are merely critical objections to the theory of selection, very similar to those frequently urged before, but more precisely stated.(52) The third is intended to show that there is in the forms of life themselves, as a faculty of adaptation peculiar to them, a primary purposiveness, which is unquestionably active throughout the lifetime and development of every individual, but which is also the deepest cause of "phylogenesis," or the formation of a race. This doctrine makes both the Darwinian and Lamarckian theories merely secondary. For the phenomena which suggest the Lamarckian interpretation presuppose this most essential factor-the primary adaptiveness. Wolff concludes with a very striking instance-discovered by himself-of this primary adaptiveness of the organism-the regeneration of the lens in the newt's eye.

More comprehensively, but from a precisely similar standpoint, Driesch has followed up the discussion of this problem.(53) He is, of all modern investigators, perhaps the one who has most persistently and thoroughly worked out the problem of causal and teleological interpretation, and he has also thrown much light on the scientific and epistemological aspects of the problem. That he could, in a recent volume of the "Biologisches Zentralblatt," write a respectful and sympathetic exposition of the Hegelian nature-philosophy-as regards its aims, though not its methods-is as remarkable a symptom as we can instance of the modern trend of views and opinions.(54)

Contrast Between Darwinian and Post-Darwinian Views.

The new views that have thus arisen have been definitely summarised and clearly contrasted with Darwinism by the botanist Korschinsky. He died before completing his general work, "Heterogenesis und Evolution," but he has elsewhere(55) given an excellent summary of his results, which we append in abstract.

DARWIN. (1) Everything organic is capable of variation. Variations arise in part from internal, in part from external causes. They are slight, inconspicuous, individual differences.

KORSCHINSKY AND THE MODERNS. (1) Everything organic is capable of variation. This capability is a fundamental, inherent character of living forms in general, and is independent of external conditions. It is usually kept latent by "heredity," but occasionally breaks forth in sudden variations.

DARWIN. (2) The struggle for existence. This combines, increases, fixes useful variations, and eliminates the useless. All the characters and peculiarities of a finished species are the results of long-continued selection; they must therefore be adapted to the external conditions.

KORSCHINSKY AND THE MODERNS. (2) Saltatory variations.-These are, under favourable circ.u.mstances, the starting-point of new and constant races.

The characters may sometimes be useful, sometimes quite indifferent, neither advantageous nor disadvantageous. Sometimes they are not in harmony with external circ.u.mstances.

DARWIN. (3) The species is subject to constant variation. It is continually subject to selection and augmentation of its characters. Hence again the origin of new species.

KORSCHINSKY AND THE MODERNS. (3) All fully developed species persist, but through heterogenesis a splitting up into new forms may take place, and this is accompanied by a disturbance of the vital equilibrium. The new state is at first insecure and fluctuating, and only gradually becomes stable. Thus new forms and races arise with gradual consolidation of their const.i.tution.

DARWIN. (4) The sharper and more acute the effect of the environment, the keener is the struggle for existence, and the more rapidly and certainly do new forms arise.

KORSCHINSKY AND THE MODERNS. (4) Only in specially favourable conditions, only when the struggle for existence is weak, or when there is none, can new forms arise and become fixed. When the conditions are severe no new forms arise, or if they do they are speedily eliminated.

DARWIN. (5) The chief condition of evolution is therefore the struggle for existence and the selection which this involves.

KORSCHINSKY AND THE MODERNS. (5) The struggle for existence simply decimates the overwhelming abundance of possible forms. Where it occurs it prevents the establishment of new variations, and in reality stands in the way of new developments. It is rather an unfavourable than an advantageous factor.

DARWIN. (6) If there were no struggle for existence there would be no adaptation, no perfecting.

KORSCHINSKY AND THE MODERNS. (6) Were there no struggle for existence, there would be no destruction of new forms, or of forms in process of arising. The world of organisms would then be a colossal genealogical tree of enormous luxuriance, and with an incalculable wealth of forms.

DARWIN. (7) Progress in nature, the "perfecting" of organisms, is only an increasingly complex and ever more perfect adaptation to the external circ.u.mstances. It is attained by purely mechanical methods, by an acc.u.mulation of the variations most useful at the time.

KORSCHINSKY AND THE MODERNS. (7) The adaptation which the struggle for existence brings about has nothing to do with perfecting, for the organisms which are physiologically and morphologically higher are by no means always better adapted to external circ.u.mstances than those lower in the scale. Evolution cannot be explained mechanically. The origin of higher forms from lower is only possible if there is a tendency to progress innate in the organism itself. This tendency is nearly related to or identical with the tendency to variation. It compels the organism to perfect itself as far as external circ.u.mstances will permit.

All this implies an admission of evolution and of descent, but a setting aside of Darwinism proper as an unsuccessful hypothesis, and a positive recognition of an endeavour after an aim, internal causes, and teleology in nature, as against fortuitous and superficial factors. This opens up a vista into the background of things, and thereby yields to the religious conception all that a study of nature can yield-namely, an acknowledgment of the possibility and legitimacy of interpreting the world in a religious sense, and a.s.sistance in so doing.