ickelungsgeschichte des Schweines,"
Schwalbe's _Morphol. Arbeiten_, iii., 1893, and v.,
1895.

_Normentafeln zur Entwickelungsgeschichte des
Schweines_, Jena, 1897.

"Das biogenetische Grundgesetz und die Cenogenese,"
_Ergebn. Anat. Entw._, vii., pp. 722-92, 1897.

"U. d. Entwickelungsgrad der Organe," _Handb. vergl.
exper. Entwick. der Wirbelthiere_, iii., 3, pp. 131-48,
1906.

[531] "Beitraege zur Embryologie der Wiederkaeuer," _Arch.
Anat. Entw._, 1889.

[532] "Die individ. Variation d. Wirbeltierembryo,"
_Morph. Arbeit._, v., 1895.

[533] "U. Variabilitaet u. Wachstum d. embryonalen
Koerpers," _Morph. Jahrb._, xxiv., 1896.

[534] "Gastrulation u. Keimblaetterbildung 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" (Mueller'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 Koerperform_, Leipzig, 1874.

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

[541] Quoted by Hertwig. See also K. Goebel, "Die
Gru