IV PREFACE. 



have been omitted in order to bring under discussion as many 

 as possible of the essential problems. 



The book is not intended to be a complete treatise upon 

 paleontology, nor a detailed report of the relation of fossils to 

 geological formations or to time. It is rather a reconnaissance 

 of a fascinating region, from which the few explorers who have 

 already penetrated it have brought back accounts of the most 

 remarkable and unexpected discoveries. A reconnaissance 

 aims to discover the characteristic features and the relative 

 importance of the various elements making up the territory 

 traversed, and is merely introductory to a more minute and 

 careful survey; its purpose is to aid the judgment, to direct 

 the 'jcourse of further research, and when difficulties of 

 travel and distances are great, it is particularly useful in pre- 

 venting distraction from the most expeditious way to the facts 

 of chief importance. 



The tendency of modern science is now, and for more 

 than a quarter of a century has been, so much to specializa- 

 tion, and our minds have become so fascinated by the minute 

 and the particular, that our common judgments of the true 

 proportion of things have become more or less distorted. 

 Theories and ideas which have been drummed into our ears 

 have come to appear the most important truths in the world, 

 and all our;, thoughts have become colored by them. We 

 cannot reaii he newspapers or listen to the talk on the street 

 without being convinced that the thought of the people, how- 

 ever little they may know of the sciences involved, is thus 

 biased by current theories about life and organisms. The 

 bearing of biological theories upon our judgments of the right- 

 ness or wrongness of conduct, both of ourselves and of so- 

 ciety, is too direct to admit of any uncertainty regarding the 

 validity of their foundations or their precise import. While 

 the facts and phenomena upon which some of the theories rest 

 are purely biological, others of them, which concern man 

 most intimately, have their chief evidence in the historical 

 records of geology. 



Among the latter none is more important than those gath- 

 ered about the phenomena of evolution ; but it is evident 

 upon reflection that the biologist proper, who deals alone 



