HISTORICAL GEOLOGY 119 



great changes wrought had been gradual, differing in no essen- 

 tial respect from those still in progress. Strangely enough, the 

 corollary to this proposition, that life, too, had been continuous 

 on the earth, formed at that date no part of the common stock 

 of knowledge. In the physical world, the great law of 'cor- 

 relation of forces' had been announced, and widely accepted; 

 but in the organic world, the dogma of the miraculous creation 

 of each separate species still held sway." 



Evolutionary Period. This period begins with 1860 

 and the publication of Darwin's Origin of Species (late 

 in 1859). It is the period of modern paleontology, and is 

 dominated by the belief that universal laws pervade not 

 only inorganic matter, but all life as well. Louis Agas- 

 siz had been in America fourteen years when Darwin's 

 book appeared, and his wonderful influence in bringing 

 the zoology of our country to a high stand and the 

 further influence he exerted through his students was 

 bound to react beneficially on invertebrate paleontology. 

 Shortly after the beginning of this period, or in 1867, 

 Alpheus Hyatt, one of Agassiz's students, began to apply 

 the study of embryology to fossil cephalopods, showing 

 clearly that these shells retain a great deal of their 

 growth stages or ontogeny. This method of study was 

 then followed by R. T. Jackson, C. E. Beecher, and J, 

 P. Smith, and has been productive of natural classifica- 

 tions of the Cephalopoda, Brachiopoda, Trilobita, and 

 Echinoidea. 



The dominant invertebrate paleontologist of this 

 period was of course James Hall, who described about 

 5000 species of American Paleozoic fossils. He also 

 built up the New York State Museum, while around his 

 private collections of fossils have been developed the 

 American Museum of Natural History in New York City 

 and the Walker Museum at the University of Chicago. 

 In his most important laboratory of paleontology at 

 Albany, there have been trained either wholly or in 

 part the following paleontologists: F. B. Meek, C. A. 

 White, E. P. Whitfield, C. D. Walcott, C. E. Beecher, 

 John M. Clarke, and Charles Schuchert. 



In Canada, through the work of the Geological Survey 

 of the Dominion, came the paleontologists Elkanah 

 Billings and, later on, J. F. Whiteaves. The "father of 



