He lays weight on what he calls the principle of finality, "puissance mysterieuse, indeterminee; fatalite pour les uns; pour les autres volonte providentielle, dont l'action incessante sur les etres vivantes determine, a toutes les epoques de l'existence du monde, la forme, le volume, et la duree de chacun d'eux, en raison de sa destinee dans l'ordre de choses dont il fait partie.
C'est cette puissance qui harmonise chaque membre a l'ensemble, en l'appropriant a la fonction qu'il doit remplir dans l'organisme general de la nature, fonction qui est pour lui sa raison d'etre." (From references in Bronn's "Untersuchungen uber die Entwickelungs-Gesetze", it appears that the celebrated botanist and palaeontologist Unger published, in 1852, his belief that species undergo development and modification.

Dalton, likewise, in Pander and Dalton's work on Fossil Sloths, expressed, in 1821, a similar belief.

Similar views have, as is well known, been maintained by Oken in his mystical "Natur-Philosophie".
From other references in Godron's work "Sur l'Espece", it seems that Bory St.Vincent, Burdach, Poiret and Fries, have all admitted that new species are continually being produced.

I may add, that of the thirty-four authors named in this Historical Sketch, who believe in the modification of species, or at least disbelieve in separate acts of creation, twenty-seven have written on special branches of natural history or geology.) In 1853 a celebrated geologist, Count Keyserling ("Bulletin de la Soc.
Geolog.", 2nd Ser., tom.x, page 357), suggested that as new diseases, supposed to have been caused by some miasma have arisen and spread over the world, so at certain periods the germs of existing species may have been chemically affected by circumambient molecules of a particular nature, and thus have given rise to new forms.
In this same year, 1853, Dr.Schaaffhausen published an excellent pamphlet ("Verhand.des Naturhist.Vereins der Preuss.  Rheinlands", etc.), in which he maintains the development of organic forms on the earth.

He infers that many species have kept true for long periods, whereas a few have become modified.