[531] "Beiträge zur Embryologie der Wiederkäuer," Arch. Anat. Entw., 1889.
[532] "Die individ. Variation d. Wirbeltierembryo," Morph. Arbeit., v., 1895.
[533] "U. Variabilität u. Wachstum d. embryonalen Körpers," Morph. Jahrb., xxiv., 1896.
[534] "Gastrulation u. Keimblätterbildung der Emys lutaria taurica," Morph. Arbeit., i., 1891. "Kainogenese," Morph. Arbeit., vii., pp. 1-156, 1897, and also separately. Biomechanik, erschlossen aus dem Prinzipe der Organogenese, Jena, 1898.
[535] This law was foreshadowed by Reichert in 1837, when he wrote:—"We notice in our investigation of embryos of different animal forms that it is those organs, those systems, which in the fully developed individual are peculiarly perfect, that in their earliest rudiments and also throughout the whole course of their development appear with the most striking distinctness" (Müller's Archiv, p. 135, 1837). See also his Entwick. Kopf. nackt. Amphib., p. 198, 1838. So, too, Rathke notes how the elongated shape of the snake appears even in very early embryonic stages (Entwick. Natter., p. 111, 1839).
[536] Quoted by Keibel (p. 790, 1897) from the Biomechanik.
[537] Die Zelle und die Gewebe, Jena, 1898, and the subsequent editions of this text-book, published under the title of Allgemeine Biologie. Die Entwickelung der Biologie im neunzehnten Jahrhundert, Jena, 1900, 2nd ed., 1908. "Ueber die Stellung der vergl. Entwickelungslehre zur vergl. Anatomie, zur Systematik und Descendenztheorie," Handb. vergl. exper. Entwickelungslehre der Wirbeltiere, iii., 3, pp. 149-80, Jena, 1906. (1906, b). Also in Pt. I. of Vol. I. (1906, a).
[538] An Essay on Classification, London, 1859.
[539] Unsere Körperform, Leipzig, 1874.
[540] Q.J.M.S., xxxvi., pp. 35-52, 1894.