PREFACE 



nection of the theologian Loofs, of Halle, the philologist 

 Dennert, of Godesberg, and the metaphysician Paulsen, 

 of Berlin, in the appendix to the cheap German edition 

 of the Riddle, applies equally to many other opponents 

 of the same type. These heated partisans may continue 

 to attack and calumniate my person as they will; they 

 will not hurt the sacred cause of truth in which I 

 labor. 



Much more interesting to me than these attacks were 

 the innumerable letters which I have received from 

 thoughtful readers of the Riddle during the last five 

 years, and particularly since the appearance of a popular 

 edition. Of these I have already received more than five 

 thousand. At first I conscientiously replied to each of 

 these correspondents, but I had at length to content 

 myself with sending a printed slip with the intimation 

 that my time and strength did not permit me to make 

 an adequate reply. However, though this correspond- 

 ence was very exacting, it afforded a very welcome proof 

 of the lively sympathy of a large number of readers with 

 the aim of the monistic philosophy, and a very interest- 

 ing insight into the mental attitude of the most varied 

 classes of readers. I especially noticed that the same re- 

 marks and questions occurred in many of these five 

 thousand letters, very often expressed in the same terms. 

 Most of the inquiries related to biological questions, 

 which I had cursorily and inadequately touched both 

 in The Riddle of the Universe and The History of Cre- 

 ation. The natural desire to remedy these deficien- 

 cies of my earlier writings and give a general reply 

 to my interrogators was the immediate cause of 

 the writing of the present work on The Wonders of 

 Life. 



I was confirmed in this design by the circumstance 

 that another scientist, the botanist Johannes Reinke, of 

 Kiel, had published two works in which he had treated 



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