INTRODUCTION TO THE AMERICAN REVISED EDITION ix 



Like Professor Hesse, we have been gripped by the work with an 

 increasing hold, and in place of the mere translation originally 

 planned, the lapse of time and our growing interest have led us to 

 examine critically the material translated in so far as our time and 

 knowledge permitted. Further, we have incorporated information which 

 had escaped Dr. Hesse's attention, and particularly new material 

 which has appeared since 1924. In the latter effort we have been 

 aided by the ambitious program of Biological Abstracts, which since 

 1926 has attempted to survey the current ecological literature of the 

 world. 



The changes from the original are extensive. We have revised 

 freely all parts where we have special knowledge either because of 

 our varied and somewhat extensive first-hand experience or on account 

 of still more varied and extensive reading. The final revision of the 

 manuscript alone, which has just been completed, resulted in a change 

 of about ten per cent of the text which was already greatly changed 

 from the original close translation. 



After some hesitation we decided not to include in the present text 

 materials with which we are not in accord. This involves great respon- 

 sibility, but the sponsoring of another's ideas of which we do not 

 approve is unthinkable and the presentation of our unedited trans- 

 lation with frank reservations is impracticable at this time and for 

 this work. We have given no indication of the location of changes in 

 the text since we were preparing the book for the greatest possible 

 use rather than as a means for comparing our ideas and information 

 with those of Professor Hesse. As a result of this action, the revising 

 editors and not the author must be held responsible for errors in the 

 present edition. Our willingness to assume responsibility for so much 

 of the work of the original author in fields in which we do not have 

 special knowledge and where we have not undertaken to verify all of 

 his citations will, we hope, sufficiently emphasize our confidence in 

 his scholarship. We trust further that our work has been intelligently 

 done and that the passing of Professor Hesse's well-considered text 

 through the hands of two diversely trained students of animal dis- 

 tribution has eliminated rather than accentuated errors. We wish to 

 emphasize our appreciation of Professor Hesse's cordial permission to 

 use our own judgment in making these revisions. 



Our changes have included the deletion of Lamarckian interpreta- 

 tions since these do not seem to us to be firmly established. We have 

 emphasized the theory of marked climatic variations during the world's 

 history and the stability of the present ocean basins more than was 

 done in the original and have stressed Matthew's theory of the 



