"The Myxomycetæ may be regarded as the organic group in which the forces of heredity,—whatever these forces may be—are at their maximum: they have responded as little as possible to the influence of their environment."
To the same effect speaks Professor Paulesco of Bucharest, of other elementary organisms.[328]
What is still more remarkable, these same organisms are extremely sensitive to altered conditions of environment, which have a direct and immediate influence, gravely modifying their morphological and physiological characters, changes in respect of light, minute alterations of temperature, or the introduction of a new chemical substance, even in infinitesimal quantity, frequently causing them to assume forms very different from the specific type, and profoundly modifying their nutritive processes.
Here, it was at first thought, when Pasteur revealed their history, is clear evidence of specific transformation. But he presently convinced himself and others that it is not so, for although liable to assume such polymorphic forms according to the conditions in which they find themselves, there is no alteration of specific nature, and if the original circumstances be restored, the original forms reappear—"une élasticité functionelle de la cellule lui permettant de se plier à des conditions variées d'existence sans changer d'être." (Pasteur.)
As M. Duclaux adds:[329]
"La notion d'espèce ne disparait pas pour cela. La variabilité est un caractère comme un autre, bien que plus[{281}] difficile à inscrire dans la classification, et une espèce est aussi bien définie par les sensibilités diverses qu'elle manifeste que par la petite liste des mots et de propriétés dans laquelle on croyait pouvoir autrefois enfermer toute son histoire.... La lien de l'espèce c'est la loi qui préside à ces changements, et la variété des formes et des fonctions n'est pas du tout en contradiction avec l'unité de l'espèce."
B. Note on Chap. XV. [p. 203].
Since the foregoing pages have been in type there has come to hand the New York Literary Digest of January 23, 1904, containing the following article (p. 119).
"Are the Days of Darwinism Numbered?"
The recent death of Herbert Spencer lends special timeliness to the above topic, which is being actively debated just now in German theological circles. The immediate cause of the revival of interest in the present status of the Darwinian theory is found in a lengthy article by the veteran philosopher, Edward von Hartmann, which appears in Oswald's Annalen der Naturphilosophie (vol. ii. 1903), under the title 'Der Niedergang der Darwinismus' ('The Passing of Darwinism'). That the famous 'philosopher of the unconscious' is not prejudiced in favour of biblical views has been more than clear since the publication of his Selbstzersetzung der Christentums ('Disintegration of Christianity') in 1874. Hartmann in his new article has this to say—