156 ZOOLOGY 



was mild, and the number of species of plants and ani- 

 mals existing was immense. The flora had become 

 varied enough to permit innumerable adaptive modifi- 

 cations in the insect world, - - species living on particu- 

 lar parts of particular plants. Life had flowed into 

 almost every channel of opportunity. Then at the end 

 of the Tertiary, during a relatively short period which 

 we separate as the Quaternary, came a succession of 

 glacial epochs, covering the northern regions with ice. 

 The consequent impoverishment of the biota has not 

 been wholly recovered from to this day. Nevertheless, 

 in the presence of hard times, and doubtless partly in 

 consequence of them, man developed. Here was a 

 being who could in a measure defy nature ; who could 

 up to a certain point create his own environment and 

 consequently take possession of the earth. The age 

 of man ought to be regarded as part of the Tertiary, 

 but this egotistical creature must needs set it apart, 

 recognizing a grand division of geological time since 

 he arrived. 



References 



WALCOTT, C. D. "Evidences of Primitive Life." Smithsonian Report for 



SCHUCHERT, CHARLES. "Paleogeography of North America." Bulletin 



Geological Society of America, Vol. 2O, 1910. 

 SCHUCHERT, CHARLES, and BARRELL, JOSEPH. "A Revised Geologic Time 



Table for North America." American Journal of Science, July, 1914. 

 MATTHEW, W. D. "Climate and Evolution." Annals New York Academy 



of Science. Vol. XXIV. 1915. 



OSBORN, H. F. The Age of Mammals. The Macmillan Company. 1910. 

 MATTHEW, W. D. " Dinosaurs." Handbook of American Museum of Natural 



History. New York, 1915. 



