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. Butterflies in particular, and especially their markings and coloration, are taken as illustrations. In the Darwinian theory of “mimicry” these played a brilliant part. The great resemblance [pg 175] 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 association 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 illustrations 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 butterfly'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 butterfly 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 embarrassment of “pseudomimicry.” [pg 176] Some butterflies 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 butterflies are not wood-butterflies 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 Schöpfung 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, Kassowitz, 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 passively waiting for natural selection and the continual accumulation 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 [pg 178] against cold or heat, to “regenerate” lost parts, often to replace entire organs that have been lost, and, under certain circumstances, 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 illustrations that are being adduced, that must force investigation to pass 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 illustration, 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 assume the colour of the substratum beneath it (soles, grasshoppers), 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 butterfly pupæ), and even that of the brightly coloured sheets of paper amidst which it is kept imprisoned. Certain spiders assume 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 pronounced critic of Darwinism, especially in the form of Weismannism. [pg 180] As far back as 1896, in a lecture “On the present position of Darwinism,” in which he dealt only with Weismann, he criticised and analysed 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.”