PREFACE. 



THE world of to-day is the product of the past 

 and the foundation of the future. We who live to- 

 day can only judge of the past by inference from the 

 present, and our only knowledge of the future is ob- 

 tained by observing the direction in which the world 

 seems to be trending as judged from its history. 

 Since life is the crowning phenomenon of nature its 

 study leads us closest to the hidden secrets of crea- 

 tion. The history of man has long been studied ; 

 the history of nature leading to man has only just 

 begun to claim attention. It is not long that man 

 has seen that history could be learned from other 

 sources than written records, and it is only a few 

 decades since he has conceived the idea of reading 

 the history of life from nature itself. For half a 

 century now have scientists been trying to pierce 

 the mysteries connected with the life of the past. 

 The history has not yet by any means been read, 

 but enough has been revealed to make a sketch of it, 

 as it appears to the biologist to-day, not a profitless 

 undertaking. 



Of the history which can be written to-day much 

 is uncertain, much is no more than pure hypothesis 



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