THE CRUST OF THE EAETH. 



54. Since, therefore, it appears that the globe, through a long 

 series of periods, has been tenanted successively by various races 

 and tribes, both animal and vegetable, it is a question of profound 

 interest to determine whether creative power, in the production of 

 these organic beings, has operated upon the same principles which 

 are manifested in the structure of its actual inhabitants. It might, 

 for example, be imagined that the forms of life at those distant 

 epochs, existing probably under extremely different physical con- 

 ditions, might be totally different from, and utterly incomparable 

 with, those which now prevail. Or though they might agree in 

 certain general principles and conditions, they might be expected 

 to exhibit extreme differences in many important details. A 

 survey, nevertheless, of the existing tribes, and a comparison of 

 them with the remains found, in the terrestrial strata, lead to the 

 conclusion, that though the former inhabitants of the globe 

 differed from the present in many minute details of their struc- 

 ture, yet they agreed in all the more essential principles. 



Naturalists have resolved the existing animal kingdom into four 

 primary divisions : the Vertebrates, the Articulated or Annulated, 

 the Mollusca, and the Zoophytes. 



Quadrupeds, birds, and fishes, for example, are Yertebrated 

 animals ; insects, spiders, and certain shell-fish, such as crabs and 

 lobsters, present examples of Articulated animals; snails and 

 oysters are examples of Mollusca ; and star-fish, sea-blubber, and 

 corals, of the class of Zoophytes. 



Xow a due examination of the organic remains deposited in the 

 terrestrial strata leads to the conclusion, that they admit of pre- 

 cisely the same general zoological division. 



But the analogy between present and past creations is still 

 closer when those primary divisions are resolved into several 

 classes. Thus the living vertebrates are divided into mammifers, 

 birds, reptiles, amphibia, and fishes. In like manner the fossil 

 vertebrates admit of precisely the same classification. "We find 

 among them all these classes and no others. 



Again, the living articulated animals are resolved into the 

 subordinate divisions of insects, myriapodes, arachnida, Crustacea, 

 and worms of various forms. A like subdivision is applicable to 

 fossil Articulata. 



Fossil, like living, Mollusca are resolved into Cephalopodes, 

 Gasteropodes (snails), Acephala (oysters and mussels), Bryozoaria 

 (plumatella), and others. In fine, the Zoophytes, fossil as well as 

 living, are resolved into Echinodermata (sea-urchin, star-fish), 

 Polyparia (coral), Infusoria (monads), and Spongy aria (sponges), 

 all of which are found reproduced in the fossil state. 



55. But when we descend to more minute distinctions we cease 

 5S 



