58 ESSAY ON CLASSIFICATION 



To me these facts show that the phenomena of life are manifested 

 in the physical world and not through or by it; that organized beings 

 are made to conquer and assimilate to themselves the materials of 

 the inorganic world; that they maintain their original characteristics, 

 notwithstanding the unceasing action of physical agents upon them. 

 And I confess I cannot comprehend how beings so entirely independ- 

 ent of these influences could be produced by them. 



SECTION XV 



PERMANENCY OF SPECIFIC PECULIARITIES 

 IN ALL ORGANIZED BEINGS 



It was a great step in the progress of science when it was ascer- 

 tained that species have fixed characters and that they do not change 

 in the course of time. But this fact, for which we are indebted to 

 Cuvier,'^^ has acquired a still greater importance since it has also 

 been established that even the most extraordinary changes in the 

 mode of existence and in the conditions under ^vhich animals may 

 be placed have no more influence upon their essential characters 

 than the lapse of time. 



The facts bearing upon these two subjects are too well known 

 now to require special illustration. I will, therefore, allude only to a 

 few points, to avoid even the possibility of a misapprehension of my 

 statements. That animals of different geological periods differ specific- 

 ally, en masse, from those of preceding or following formations is a 

 fact satisfactorily ascertained. Between two successive geological peri- 

 ods, then, changes have taken place among animals and plants. But 

 none of those primordial forms of life, which naturalists call species, 

 are known to have changed during any of these periods. It cannot 

 be denied that the species of different successive periods are supposed 

 by some naturalists to derive their distinguishing features from 

 changes which have taken place in those of preceding ages; but this is 

 a mere supposition, supported neither by physiological nor by geo- 

 logical evidence, and the assumption that animals and plants may 

 change in a similar manner during one and the same period is equally 



''^ Recherches sur les ossemens fossiles . . . (2d ed., 5 vols., Paris, 1821-1824), I, cxli. 



