The neo-Lamarckian conflict with Darwinism has become more and more acute in recent times, and the neo-Lamarckians have sometimes passed from contrasting rival interpretations to excluding the Darwinian factor altogether. As the particular champion of the neo-Lamarckian view, we must name Th. Eimer, the recently deceased Tübingen zoologist. His chief work is in three volumes, entitled “Die Entstehung der Arten auf Grund von Vererbung erworbener Eigenschaften, nach Gesetzen organischen Wachsens.”(43) It is a polemic against Weismannism in all details, even to the theory of “germinal selection.” Eimer follows in the footsteps of St. Hilaire, and shows what a relatively plastic and sensitive creature the organism is to the surrounding world, the conditions of nutrition and other such influences. There is in this connection a particularly instructive chapter on the physiological and other variations brought about by external influences which act as “stimuli of the nervous system.” The whole theory of Lamarck and St. Hilaire transcends—notwithstanding the protests of Eimer to the contrary—the categories of the mechanical theory of life, and this chapter does so in particular. The array of facts here marshalled as to the spontaneous self-adaptation of organisms to their environment—in relation to colour mainly—forms the most thoroughgoing refutation of Darwinism that it is possible to imagine. It is shown, too, by a wealth of examples from osteology, how use (and the necessities of the case—a consideration which again goes beyond the bounds of mere Lamarckism) may modify, increase or diminish vertebræ, ribs, skull and limbs, in short, the whole skeleton.
Kassowitz is equally keen and convinced in his opposition to natural selection, and in his comprehensive “Allgemeine Biologic”(44) he attacks orthodox Darwinism from the neo-Lamarckian standpoint. The whole of the first volume is almost chapter for chapter a critical analysis, and the polemical element rather outweighs his positive personal contribution. He criticises very severely all attempts to carry the Darwinian principle of explaining adaptations into internal and minute details, arguing against Roux’s “Struggle of Parts” and Weismann’s “Germinal Selection.” And though he himself maintains very decidedly that the ultimate aim of biology is to find a mechanical solution of the problem of life, he criticises the modern hypotheses in this direction without prejudice, and declares them unsuccessful and insufficient, inclining himself towards the “neo-vitalistic reaction” in its most recent expression. Along with Eimer and Kassowitz, we may name W. Haacke, especially in relation to his views on the acquisition and transmission of functional modifications and his thoroughgoing denial of Darwinism proper. But his work must be dealt with later in a different connection.(45)