106 ESSAY ON CLASSIFICATION. Part I. 



geology proper and of palteontology concur in the main to prove, that while the 

 globe has been at repeated intervals, and indeed frequently, though after immensely 

 long periods, altered and altered again, until it has assumed its present condition, 

 so have also animals and plants, living upon its surface, been again and again extin- 

 guished and replaced by others, until those now living were called into existence 

 with man at their head. The investigation is not in every case sufficiently com- 

 plete to show everyAvhere a coincidence between this renovation of animals and 

 plants and the great physical revolutions which have altered the general aspect of 

 the globe, but it is already extensive enough to exhibit a frequent synchronism and 

 correlation, and to warrant the expectation that it will, in the end, lead to a com- 

 plete demonstration of their mutual dependence, not as cause and effect, but as steps 

 in the same progressive development of a plan which embraces the physical as well 

 as the organic world. 



In order not to misapprehend the facts, and perhaps to fall back upon the 

 idea, that these changes may be the cause of the differences observed between the 

 fossils of different periods, it must be well understood that, wliile organized bemgs 

 exhibit through all geological formations a regular order of succession, the character 

 of which will be more fully illustrated hereafter, this succession has been from 

 time to time violently interrupted by physical disturbances, without any of these 

 altering in any way the progressive character of that succession of organized beings. 

 Truly this shows that the important, the leading feature of this whole drama is 

 the development of life,^ and that the material world affords only the elements for 

 its realization. The simultaneous disappearance of entire faunte, and the following 

 simultaneous appearance of other faunis, show further that, as all these faunae con- 

 sist of the greatest variety of types,^ in all formations, combined everywhere into 

 natural associations of animals and plants, between which there have been definite 

 relations at all times, their origin can at no time be owing to the limited influence 

 of monotonous physical causes, ever acting in the same way. Here, again, the 

 intervention of a Creator is displayed in the most striking manner, in every stage 

 of the history of the world. 



^ Dana, (J. D.,) Address, q. a., p. 9i, note 1. " Agassiz, (L.,) Geol. Times, q. a., p. 25. 



