[Footnote 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.] [Footnote 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.] [Footnote 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).] [Footnote 24: Paul Janet, _Les Causes finales_, Paris, 1876, p. 83.] [Footnote 25: _Ibid._ p. 80.] [Footnote 26: Darwin, _Origin of Species_, chap. ii.] [Footnote 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).] [Footnote 28: De Vries, _Die Mutationstheorie_, Leipzig, 1901-1903. Cf., by the same author, _Species and Varieties_, Chicago, 1905.] [Footnote 29: Darwin, _Origin of Species_, chap. vi.] [Footnote 30: Darwin, _Origin of Species_, chap. i.] [Footnote 31: On this homology of hair and teeth, see Brandt, "Über ... eine mutmassliche Homologie der Haare und Zahne" (_Biol. Centralblatt_, vol. xviii., 1898, especially pp. 262 ff.).] [Footnote 32: It seems, from later observations, that the transformation of Artemia is a more complex phenomenon than was first supposed. See on this subject Samter and Heymons, "Die Variation bei Artemia Salina" (_Anhang zu den Abhandlungen der k. preussischen Akad. der Wissenschaften_, 1902).] [Footnote 33: Eimer, _Orthogenesis der Schmetterlinge_, Leipzig, 1897, p. 24. Cf. _Die Entstehung der Arten_, p. 53.] [Footnote 34: Eimer, _Die Entstehung der Arten_, Jena, 1888, p. 25.] [Footnote 35: _Ibid._ pp. 165 ff.] [Footnote 36: Salensky, "Heteroblastie" (_Proc. of the Fourth International Congress of Zoology_, London, 1899, pp. 111-118). Salensky has coined this word to designate the cases in which organs that are equivalent, but of different embryological origin, are formed at the same points in animals related to each other.] [Footnote 37: Wolff, "Die Regeneration der Urodelenlinse" (_Arch. f. Entwicklungsmechanik_, i., 1895, pp. 380 ff.).]