Two volumes of the _Suites a Buffon_.

[304] _U. d. Metamorphose der Ophiuren u. Seeigel._,
Berlin, 1848. _U. d. Metamorphose der Holothurien u.
Asterien._, Berlin, 1851.

[305] As I have been unable to obtain a copy of the
_Introduction_, the passages which follow are taken from
the _Rapport_ of 1867, where Milne-Edwards gives a
complete exposition of his doctrine, sometimes in the
words of the original.

[306] This principle was first developed by Milne-Edwards
in 1827, in the _Dictionnaire classique d'Hist.
naturelle_. It was probably suggested to him by his
studies on the Crustacea, among which the principle is
so beautifully exemplified in the concentration and
specialisation of the appendages and the ganglionic
chain.

[307] Studied by Isidore Geoffroy St Hilaire in his paper
_Classification parallelique des Mammiferes, C. R. Acad.
Sci._, xx., 1845. Remarked upon by Cuvier, _Regne
animal_., i., p. 171, 1817, also by de Blainville.

[308] Cuvier et Valenciennes, _Hist. nat. des Poissons_,
i., p. 550, 1828.

[309] _Myxinoiden_, Th. I. _Abh. k. Akad. Wiss. Berlin_
for 1834, pp. 100, 110, 179, etc.

[310] _Vergl. Entw. Kopf. nackt. Amphibien_, p. 101, 1838.

[311] I have not seen the companion volume on
palaeontological progression, _Unters. ue. d.
Entwickelungsgesetze der organischen Welt waehrend der
Bildungszeit unserer Erdoberflaeche_, Stuttgart, 1858.

[312] "Strobiloid" because of its spiral development. The
theory of the spiral growth of plants played an
important part in botanical morphology about this time.

[313] _Cf._ Meckel's Principle of progressive Evolution,
_supra_, p. 93.

[314] _System der thierischen Morphologie_, pp. 33, 457.
Also C. Bruch, _Die Wirbeltheorie des Schaedels, am
Skelette des Lachses geprueft_, Frankfort-on-Main, 1862.

[315] In France the vertebral theory was advocated by
Lavocat in his _Nouvelle Osteologie comparee de la tete
des animaux domestiques_, Toulouse, 1864. It seems also
that Lacaze-Duthiers held fast to it even in
1872--_Arch. zool. exp. gen._, i., p. 51, 1872.

[316] _An Essay on Classification_, Boston, 1857, London,
1859. He considered the classificatory categories to be
the categories of the Creator's thought, and hence
natural, and in no sense mere conventions.

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