THE 



POPULAR SCIENCE 

 MONTHLY. 



MAECH, 1878. 



INTRODUCTION AND SUCCESSION OF VERTEBRATE 



LIFE IN AMERICA. 1 



By Prof. 0. C. MARSH. 



THE origin of life and the order of succession in which its various 

 forms have appeared upon the earth offer to science its most in- 

 viting and most difficult field of research. Although the primal origin 

 of life is unknown, and may perhaps 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 domain of science to de- 

 termine 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 be- 

 longs to the higher 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. 



Taking, then, evolution as a key to the mysteries of past life on 

 the earth, I invite your attention to the subject I have chosen : "The 

 Introduction and Succession of Vertebrate Life in America." 



In the brief hour allotted to me, I could hardly hope to give more 

 than a very incomplete sketch of what is now known on this subject. 



1 An address delivered before the American Association for the Advancement of Sci- 

 ence, at Nashville, Tenn., August 30, 1877, by Prof. 0. C. Marsh, Vice-President. 

 vol. xii. 33 



