Jan. 1851), briefly gives his reason for believing that specific characters "sont fixés, pour chaque espèce, tant qu'elle se perpétue au milieu des mèmes circonstances: ils se modifient, si les circonstances ambiantes viennent à changer.' 'En résumé, l'observation des animaux sauvages démontre déjà la variabilité limité des espèces. Les expériences sur les animaux sauvages devenus domestiques, et sur les animaux domestiques redevenus sauvages, la démontrent plus clairement encore. Ces memes expériences prouvent, de plus, que les différences produites peuvent etre de valeur générique.' In his 'Hist. Nat.
Généralé (tom. ii. p. 430, 1859) he amplifies analogous conclusions.
From a circular lately issued it appears that Dr Freke, in 1851 ("Dublin Medical Press,' p. 322), propounded the doctrine that all organic beings have descended from one primordial form. His grounds of belief and treatment of the subject are wholly different from mine; but as Dr Freke has now (1861) published his Essay on the 'Origin of Species by means of Organic Affinity,' the difficult attempt to give any idea of his views would be superfluous on my part.
Mr Herbert Spencer, in an Essay (originally published in the 'Leader,'
March, 1852, and republished in his 'Essays,' in 1858), has contrasted the theories of the Creation and the Development of organic beings with remarkable skill and force. He argues from the analogy of domestic productions, from the changes which the embryos of many species undergo, from the difficulty of distinguishing species and varieties, and from the principle of general gradation, that species have been modified; and he attributes the modification to the change of circumstances. The author (1855) has also treated psychology on the principle of the necessary acquirement of each mental power and capacity by gradation.
In 1852 M. Naudin, a distinguished botanist, expressly stated, in an admirable paper on the Origin of Species ('Revue Horticole, p. 102; since partly republished in the 'Nouvelles Archives du Muséum,' tom. i.
p. 171), his belief that species are formed in an analogous manner as varieties are under cultivation; and the latter process he attributes to man's power of selection. But he does not show how selection acts under nature. He believes, like Dean Herbert, that species, when nascent, were more plastic than at present. He lays weight on what he calls the principle of finality, 'puissance mystérieuse, indéterminée; fatalitépour les uns; pour les autres volonté providentielle, dont l'action incessante sur les ètres vivants détermine, à toutes les époques de l'existence du monde, la forme, le volume, et la durée de chacun d'eux, en raison de sa destinée dans l'ordre de choses dont il fait partie. C'est cette puissance qui harmonise chaque membre à l'ensemble, en l'appropriant à la fonction qu'il doit remplir dans l'organisme général de la nature, fonction qui est pour lui sa raison d'ètre.'** From references in Bronn's 'Untersuchungen über die Entwickenlungs-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'Espéce,' it seems that Bory St Vincent, Burdach, Poiret, and Fries, have all admitted that new species are continually being produced.
In 1853 a celebrated geologist, Count Keyserling ("Bulletin de la Soc.
Gèolog.,' 2nd Ser., tom. x. p. 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,' &c.), 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. The distinction of species he explains by the destruction of intermediate graduated forms. 'Thus living plants and animals are not separated from the extinct by new creations, but are to be regarded as their descendants through continued reproduction.'
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.
A well-known French botanist, M. Lecoq, writes in 1854 ('Etudes sur Géograph. Bot.,' tom. i. p. 250), 'On voit que nos recherches sur la fixité ou la variation de l'espèce, nous conduisent directement aux idées émises, par deux hommes justement célèbres, Geoffroy Saint-Hilaire et Goethe.' Some other passages scattered through M. Lecoq's large work, make it a little doubtful how far he extends his views on the modification of species.