PREFACE. V 



with the organisms now living upon the earth, must rest with 

 a theoretical interpretation of the laws of evolution. To the 

 geologist the records of evolution are open for direct exami- 

 nation, and geological biology is a scientific treatment of the 

 observed facts of evolution. 



While there are no end of books on evolution, and modern 

 biologists seem content to assume that some theory of evolu- 

 tion is true, without being able to decide which it shall be ; 

 and although the students of sociology, the moralist, and the 

 theologian are basing their theories about man on the " work- 

 ing hypotheses" of the naturalist as if " law and gospel," it 

 seems to have escaped serious attention that we have open 

 for study a genuine record of the actual evolution of organ- 

 isms, extending from near the beginning of life up to the 

 present time. Men have been speculating in all conceivable 

 directions to form some theory as to how evolution ought to 

 work, and as to what the history of organisms ought to be : it 

 is the province of geological biology to tell us what the his- 

 tory of organisms has actually been. The geologist does not 

 ask what is the theory of evolution, but what are the facts of 

 evolution. " The primary and direct evidence in favor of 

 evolution can be furnished only by paleontology. The geo- 

 logical record, so soon as it approaches completeness, must, 

 when properly questioned, yield either an affirmative or a 

 negative answer: if evolution has taken place, there will its 

 mark be left ; if it has not taken place, there will lie its refu- 

 tation." The late Professor Huxley, who framed this most 

 true and pertinent sentence, knew very well the evidence 

 which those records furnish, although he often treated evolu- 

 tion as if it were a doctrine requiring argumentative defense, 

 rather than a science which only needs elucidation. 



The treatment which evolution receives in these pages is 

 designed for those who wish to know what the chief facts and 

 factors of evolution are, not those who are looking for further 

 debate of the arguments either for or against a theory of evo- 

 lution. To the student who approaches the subject from the 

 historical side evolution becomes the very key to the mystery 

 of organic life. The phenomena of growth are fairly well 

 understood, the development of the individual has been sys- 



