nnere Skelet," Meckel's
_Archiv fuer Anat. u. Physiol._, pp. 327-76, 1826. See,
too, his _Entwickelungsgeschichte_, i., pp. 181, ff.

[178] Von Baer wrote an appreciative biography of Cuvier,
published posthumously in 1897, _Lebensgeschichte
Cuviers_, ed. L. Stieda. French trans. in _Ann. Sci.
Nat._ (_Zool._), ix., 1907.

[179] Cuvier et Valenciennes, _Histoire naturelle des
Poissons_, i., p. 550.

[180] _Mem. Mus. d'Hist. Nat._, iii., pp. 98-119, 1817.

[181] _Lecons d'Anatomie comparee_, 3rd ed., vol. i., p.
414, Bruxelles, 1836.

[182] In the aforementioned paper in Mueller's _Archiv_ he
criticises Carus vigorously and is sarcastic on
Geoffroy.

CHAPTER X

THE EMBRYOLOGICAL CRITERION

Pander's work of 1817 was the forerunner of an embryological period in
which men's hopes and interest centred round the study of development.
"With bewilderment we saw ourselves transported to the strange soil of a
new world," wrote Pander, and many shared his hopeful enthusiasm. K. E.
von Baer's _Entwickelungsgeschichte_ was by far the greatest product of
this time, but it stands in a measure apart; we have in this chapter to
consider the lesser men who were Baer's contemporaries, friends,
followers or critics.

It was largely a German science, this new embryology, and its leaders
were all personally acquainted. Pander, von Baer and Rathke were on
friendly terms with one another; von Baer dedicated his master-work to
Pander; Rathke dedicated the second volume of his _Abhandlungen_ to von
Baer. Interest in the new science was, however, not confined to Germany.
In Italy, Rusconi commenced in 1817 his pioneer researches on the
development of the Amphibia with a _Descrizione anatomica degli organi
della circolazione delle larve delle Salamandre aquatiche_ (Pavia), in
which he traced the metamorphoses of the aortic arches. This was
followed in 1822 by his _Amours des Salamandres aquatiques_ (Milan), and
in 1826 by his memoir _Du developpement de la grenouille_ (Milan). In
this last paper he described how the dark upper hemisphere of the frog's
egg grows down over the lower white hemisphere and leaves free only the
yolk plug; he observed the segmentation cavity and the archenteron, but
thought that the former became the alimentary canal; he observed and
interpreted rightly the formation of the medullary folds. The circular
blastopore in the frog in later years often