PREFACE 7 



that the reader who desires to go further into the 

 matter will find every assistance. With the same 

 object of making the text clear the various animals 

 have been indicated, as far as possible, by their 

 popular names, but their scientific titles will be found 

 in the index at the end of the work. 



The difficulty of many of the questions treated 

 imposed a yet further condition. Problems that are 

 not easily grappled could not very well be put at 

 once before the reader. The book gradually educates 

 him up to the level of these. Starting from familiar 

 objects, it leads him on, almost unconsciously, to 

 problems of increasing difficulty, until he is at length 

 in a position to form an opinion on even the most 

 difficult. 



And as it is the purpose of this work to elucidate 

 the theory of evolution only by means of observation, 

 to convince those only who have some insight into 

 the inexhaustible facts of nature that bear witness to 

 it, as many as possible of these facts have been 

 introduced. Nature herself shall teach the reader the 

 truth of evolution. On this account, the first part of 

 the work has been divided, not into problems, but 

 according to groups of animals. These animals, 

 moreover, are generally the familiar ones of our own 

 country. Our indigenous animal-life has been treated 

 very fully. Plants have only been dealt with in so 



