PREFACE TO THE SECOND EDITION. 



SOONER than we dared to hope, a large German edition 

 of this work has been exhausted; the English, Italian, and 

 Russian editions also have found a large sale. We accept 

 this as an indication of the practical value of the book. 

 With special pleasure we have observed in the numerous 

 reviews of the book that its reformative tendency in regard 

 to the grouping of varieties of bacteria, the strict division 

 of 'the system especially, the rational naming of bacteria, 

 etc., have found warm praise. The text-books of Heim 

 and Mez have accepted our nomenclature entirely or in 

 part. For many new names in Fliigge-Kruse's work, 

 which appeared a few months after ours, according to the 

 rule of botanical systems, the priority remains with us. 

 Moreover, where we have found that properly selected 

 names, older than those which we chose in the first 

 edition, existed, we have naturally strictly adhered to the 

 rule of priority. We affirm with pleasure that, because of 

 our exact observations and of reliable statements in the 

 literature, the carefully championed view of the exceed- 

 ingly great variability of bacteria finds more and more 

 recognition, and that the authors who to-day describe 

 "new species " are in the main fewer, as is witnessed by 

 the intelligent views advanced by the collection of bac- 

 teriologists in New York in 1895 (C. B. xx, 450). 



The opinion advanced from an esteemed source, that the 

 constant emphasis of variability, of the limits of our knowl- 

 edge, and of the uncertainty of known methods, may some- 

 times discourage the beginner, may not be entirely un- 

 founded. Yet we believe this absolute frankness to be an 

 advantage, even if thereby the dogmatic sharpness of the 

 statements should sometimes suffer. With beginners one 



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