INTRODUCTION AND SUCCESSION OF VERTEBRATE 

 LIFE IN AMERICA. 



The origin of life, and tlic order of succession in which its 

 various forms have appeared upon the earth, offer to science 

 its most inviting and most difficult field of research. 

 Although the primal origin of life is unknown, and may per- 

 haps never be known, yet no one has a right to say how much 

 of the mystery now surrounding it science cannot remove. 

 It is certainly within the domairt of science to determine when 

 the earth was first fitted to receive life, and in what form the 

 earliest life began. To trace that life in its manifold changes 

 through past ages to the present is a more difficult task, but 

 one from which modern science does not shrink. In this wide 

 field, every earnest effort will meet some degree of success ; 

 every year will add new and important facts ; and every 

 generation will bring to light some law, in accordance with 

 which ancient life has been changed into life as we see it 

 around us to-day. That such a development has taken place, 

 no one will doubt who has carefully traced any single group 

 of animals through its past history, as recorded in the crust of 

 the earth. The evidence will be especially conclusive, if the 

 group selected belongs to the higlier forms of life, which are 

 sensitive to every change in their surroundings. But I am sure 

 I need offer here no argument for evolution ; since to doubt 

 evolution to-day is to doubt science, and science is only another 

 name for truth. 



