[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" (Muller'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 t.i.tle 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 Cla.s.sification_, London, 1859.

[539] _Unsere Korperform_, Leipzig, 1874.

[540] _Q.J.M.S._, x.x.xvi., pp. 35-52, 1894.

[541] Quoted by Hertwig. See also K. Goebel, "Die Grundprobleme der heutigen Pflanzenmorphologie," _Biol.

Centrbl._, xxv., pp. 65-83, 1905.

[542] This is also emphasised by Fleischmann in his critical study of evolutionary morphology ent.i.tled _Die Descendenztheorie_, Leipzig, 1901.

[543] The same remark applies to the bulk of speculation as to the factors of evolution, with the exception of the contributions made to evolution theory by the palaeontologists by profession, such as Cope.

[544] _Les Transformations du Monde animal_, Paris, 1907.

[545] "Malacology _versus_ Palaeoconchology," _Proc.

Malacological Soc._, viii., pp. 66-83, 1908.

[546] Particularly by E. Perrier, "La Tachygenese," _Ann.

Sci. nat._ (_Zool._) (8), xvi., 1903.

[547] _Monatsber. k. Akad. Wiss._, Berlin, pp. 474-504, 1866.

[548] _Geognost. u. Palaeont. Beitrage_, ii., Heft 2, pp.

181-256, 1869.

[549] _Abhand. k.k. Geol. Reichsanstalt_, vii., Wien, 1875.

[550] The case for polyphyletism is very strongly put by G. Steinmann in his book, _Die geologischen Grundlagen der Abstammungslehre_, Leipzig, 1908.

[551] The steps in this chronological variation were termed by Waagen "mutations."

[552] _The Age of Mammals in Europe, Asia, and North America_, New York, 1910.

[553] _Origin of Species_, 6th ed., Chap. IV.