But criticism of Weismann's hypothesis is not to be an end in itself; I am more anxious to show the lines upon which, as I think, the real meaning of the process of organic development will come to be learned. In a second section, therefore, I shall explain my own views in greater detail, and, as I hope, place them on a firmer foundation than formerly was possible. FOOTNOTES: [1] Wilhelm Roux in _Zeitschrift für Biologie_, vol. xxi. (1885): _Zür Orientirung ueber einige Probleme der Embryonalen Entwicklung._ [2] See Weismann's _Collected Essays_, Clarendon Press (2nd edit.), vol. i., 1891, vol. ii., 1892; and Weismann's _Germplasm_, Walter Scott's Contemporary Science Series, 1893. The references in this translation are to the latter volume. [3] _The Germplasm_, p. 137. [4] _Ibid._, p. 138. [5] The ideas expressed in this book may be found, in an elementary condition, in various publications of my own, and written in conjunction with my brother, Richard Hertwig: Oscar and Richard Hertwig, _Die Actinien_; Jena, 1879 (pp. 203-217). Oscar Hertwig, _Das Problem der Befruchtung und der Isotropie des Eies, eine Theorie der Vererbung_; Jena, 1884. Oscar Hertwig, _Vergleich der Ei- und Samenbildung bei Nematoden, Arch. f. Mikrosk. Anatomie_, vol. xxxvi., 1890, pp. 77-128. Oscar Hertwig, _Urmund und Spina bifida, Arch. f. Mikrosk. Anatomie_, vol. xxxix., 1892, pp. 476-492. Oscar Hertwig, _Aeltere und neuere Entwicklungstheorien_; Berlin, 1892. Oscar Hertwig, _The Cell_: Sonnenschein; London, 1895. Oscar Hertwig, _Ueber den Werth der ersten Furchungszellen für die Organbildung des Embryo, Arch. f. Mikrosk. Anatomie_, vol. xlii., 1893. The chief other writers to whom I refer are: Herbert Spencer, _Principles of Biology_. Darwin, _Pangenesis, a Provisional Hypothesis (in Variation of Plants and Animals under Domestication)_. Haeckel, _Die Perigenesis der Plastidule_. Weismann, _loc. cit._, p. 8. Naegeli, _Mechanisch-physiologische Theorie der Abstammungslehre_; München, 1884. Strasburger, _Neue Untersuchungen ueber den Befruchtungsvorgang bei den Phanerogamen als Grundlage für eine Theorie der Zeugung_, 1884. H. de Vries, _Intracellulare Pangenesis_. W. His, _Unsere Körperform und das physiologische Problem ihrer Entstehung_, 1874. W. Roux, _loc. cit._, p. 6. Driesch, _loc. cit._, p. 48. [6] An English translation, _The Cell_, was published by Swan Sonnenschein and Co. in 1895. PART I. WEISMANN'S THEORY OF THE GERMPLASM AND DOCTRINE OF DETERMINANTS.