His “Beiträge 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 unassailable 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 [pg 181] 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 [pg 182] 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 [pg 183] 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 circumstances, 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 circumstances.
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.