26 ESSAY ON CLASSIFICATION 



have in the end proved to agree with the reaUty, in spite of every 

 objection at first offered by empiric observers. 



SECTION VII 



SIMULTANEOUS EXISTENCE IN THE EARLIEST GEOLOGICAL PERIODS 

 OF ALL THE GREAT TYPES OF ANIMALS 



It was formerly believed by geologists and palaeontologists that the 

 lowest animals first made their appearance upon this globe and that 

 they were followed by higher and higher types, until man crowned 

 the series. Every geological museum, representing at all the present 

 state of our knowledge, may now furnish the evidence that this is 

 not the case. On the contrary, representatives of numerous families 

 belonging to all the four great branches of the animal kingdom, are 

 well known to have existed simultaneously in the oldest geological 

 formations.^^ Nevertheless, I well remember when I used to hear the 

 great geologists of the time assert that the Corals were the first in- 

 habitants of our globe, that Mollusks and Articulata followed in 

 order, and that Vertebrates did not appear until long after these. 

 What an extraordinary change the last thirty years have brought 

 about in our knowledge and the doctrines generally adopted respect- 

 ing the existence of animals and plants in past ages! However much 

 naturalists may still differ in their views regarding the origin, the 

 gradation, and the affinities of animals, they now all know that 

 neither Radiata, nor Mollusks, nor Articulata, have any priority one 

 over the other, as to the time of their first appearance upon earth; 

 and though some still maintain that Vertebrata originated somewhat 

 later, it is universally conceded that they were already in existence 

 toward the end of the first great epoch in the history of our globe. 

 I think it would not be difficult to show upon physiological grounds 



^Roderick Murchison, The Silurian System (London, 1839); Murchison, Sihiria. The 

 History of the Oldest Knoiun Rocks Containing Fossils (London, 1854); Murchison, 

 Phillippe E. P. de Verneuil, and Alexander von Kaiserling, The Geology of Russia in 

 Europe, and the Ural Mountains (2 vols., London, 1845); James Hall, Paleontology of 

 the State of New York (2 vols., Albany, 1847-1852); Joachim Barrande, Systeine silurien 

 du centre de la Bohcme (2 vols., Prague and Paris, 1852); Adam Sedgwick and Frederick 

 McCoy, A Synopsis of the Classification of the British Palceozoic Rocks . . . (London, 

 1855). 



