[20] Du Bois-Reymond, Über die Grenzen des Naturerkennens, Leipzig, 1892.
[21] There are really two lines to follow in contemporary neo-vitalism: on the one hand, the assertion that pure mechanism is insufficient, which assumes great authority when made by such scientists as Driesch or Reinke, for example; and, on the other hand, the hypotheses which this vitalism superposes on mechanism (the "entelechies" of Driesch, and the "dominants" of Reinke, etc.). Of these two parts, the former is perhaps the more interesting. See the admirable studies of Driesch—Die Lokalisation morphogenetischer Vorgänge, Leipzig, 1899; Die organischen Regulationen, Leipzig, 1901; Naturbegriffe und Natururteile, Leipzig, 1904; Der Vitalismus als Geschichte und als Lehre, Leipzig, 1905; and of Reinke—Die Welt als Tat, Berlin, 1899; Einleitung in die theoretische Biologie, Berlin, 1901; Philosophie der Botanik, Leipzig, 1905.
[22] P. Guérin, Les Connaissances actuelles sur la fécondation chez les phanérogames, Paris, 1904, pp. 144-148. Cf. Delage, L'Hérédité, 2nd edition, 1903, pp. 140 ff.
[23] Möbius, Beiträge zur Lehre von der Fortpflanzung der Gewächse, Jena, 1897, pp. 203-206 in particular. Cf. Hartog, "Sur les phénomènes de reproduction" (Année biologique, 1895, pp. 707-709).
[24] Paul Janet, Les Causes finales, Paris, 1876, p. 83.
[25] Ibid. p. 80.
[26] Darwin, Origin of Species, chap. ii.
[27] Bateson, Materials for the Study of Variation, London, 1894, especially pp. 567 ff. Cf. Scott, "Variations and Mutations" (American Journal of Science, Nov. 1894).
[28] De Vries, Die Mutationstheorie, Leipzig, 1901-1903. Cf., by the same author, Species and Varieties, Chicago, 1905.
[29] Darwin, Origin of Species, chap. vi.