The “Lamarckian” view as opposed to the Darwinian continues to hold its own, and indeed is more ardently supported than ever. On this view, evolution has been accomplished not by a laborious selection of the best which chanced to present itself—a selection in relation to which organisms remained passive, but rather through the exertions of the organisms themselves. It has been especially through the use and exercise of the various [pg 165] organs in response to the requirements of life, through the increased exercise of physical and mental functions, that the organism has adapted itself more diversely and more fully to the conditions of its life. What one generation acquired in differentiation of structure, in capacities and habits, through its own exertions, it handed on to the next. By cumulative inheritance there ultimately arose the fixed specific characters, and the diversity and progressive gradations of organisms have gone hand in hand with an ever increasing activity. And as with the physical so it has been with the mental. Through continual use and exercise of the functions their capacity has been increased and modified. Through the frequent repetition of voluntary actions necessary to life the habitual use of them has come about. Habits that have become fixed are correlated with habitual psychical predispositions. These, gradually handed on by inheritance to the descendants, have resulted in the marvellous instincts of animals. Instinct is inherited habit that has become fixed. Corresponding to this there is on the other hand the recognition—in theory at least—that the disuse of an organ, the non-exercising of a function leads to degeneration of structure and so co-operates in bringing about a gradual but persistent modification of the features and constitution of organisms.

These views, which have grown out of Lamarck's fundamental ideas (“Philosophie zoologique,” 1809) are now usually associated with the theory advanced chiefly [pg 166] by Etienne Geoffrey St. Hilaire (“Philosophie zoologique,” 1830), the opponent of Cuvier, and the ally of Goethe, of the direct influence of the monde ambiant. The “surrounding world,” the influences of climate, of locality, of the weather, of nutrition, of temperature, of the salinity of the water, of the moisture in the air, and all other conditions of existence, influence the living organism. And they do so not indirectly, as is implied in the process of selection, simply playing the part of a sieve, and not themselves moulding and transforming, but directly by necessitating the production of new developments in the living substance, new chemical and physiological activities, new groupings and changes of form, and new organs.

Darwin himself did not regard these two theories as opposed to the theory of selection, but utilised them as subsidiary interpretations. It is obvious, however, that at bottom they conceal an essentially different fundamental idea, which, if followed out to its logical consequences, reduces the “struggle for existence” to at most a wholly indifferent accessory circumstance. Weismann felt this, and hence his entirely consistent endeavours to show by great examples, such as the origin of flowers, the mutual adaptations of flowers and insects, the phenomena of mimicry, and many other cases, that neither the Lamarckian nor any other factor in evolution, except only natural, passive selection, suffices as an interpretation. From the Darwinian standpoint he is absolutely right, and must needs speak [pg 167] of the “omnipotence of natural selection,” for it must either be omnipotent, or it must give place to the other two factors, and retain only the significance we attributed to it in another connection (p. 157), which amounts to saying none at all. It is obvious enough why the discussion as to these factors should centre round the question of the “inheritance of acquired characters,” “acquired” either through the use or disuse of organs, the exercise or non-exercise of functions, or through the stimuli of the external world.

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 [pg 168] 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 [pg 169] 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

These neo-Lamarckian views give us a picture of the evolution of the world that is much more convincing than the strictly Darwinian one. Instead of passive and essentially unintelligent “adaptation” through the sieve of selection, we have here direct self-adaptation of organisms to the conditions of their existence, through their own continual restless activity and exertion, an ascent of their own accord to ever greater heights and perfections. A theory of this kind might easily form part of a religious conception of the world. We might think of the world with primitive tendencies and capacities, in which the potentialities of its evolution were implied, and so ordered that it had to struggle by its own exertions to achieve the full realisation of its [pg 170] possibilities, to attain to ever higher—up to the highest—forms of Being. The process of nature would thus be the direct anticipation of what occurs in the history of man and of mind. And the task set to the freedom of individual men, and to mankind as a whole, namely, to work out their own nature through their own labour and exertion, and to ascend to perfection—this deepest meaning of all individual and collective existence—would have its exact prelude and preparation in the general nature and evolution of all living creatures. The transition from these theories of nature to a teleological outlook from the highest and most human point of view is so obvious as to be almost unavoidable. And although a natural science which keeps to its own business and within its own boundaries has certainly no right to make this transition for itself, it has still less right to prevent its being made outside of its limits.