xiv EXCERPTS FROM THE ORIGINAL PREFACE 



names in the text. They are not given as faunal lists in which the 

 species are grouped with no other connection than that they come 

 from the same locality; rather the species are given as examples for 

 the formulation of general laws. In the naming of species I have 

 followed Grobben's revision of the Textbook of Zoology of C. Claus 

 (third edition, 1917). In special cases I have followed other sources; 

 e.g., for palaearctic birds, I have used E. Hartert's comprehensive 

 work. Since the different parts of the book have been taken from 

 work done at widely differing times and since there are different 

 names for many species, my knowledge has not always sufficed to 

 guarantee a correct name, so much the less since, despite all reforms, 

 zoological nomenclature is still full of contradictions. Because the use 

 of Latin names for common animals is bombastic in many cases, I 

 have frequently given the common name only. 



Inasmuch as the facts used must be drawn from a rich literature, 

 I have tried to bring together the most useful sources and have 

 appended a selected set of references to each chapter. In order not 

 to expand these citations unduly, I have given only the author and 

 the journal and, where needed, the page reference to the useful mate- 

 rial, but not the title of the paper, which is frequently foreign to the 

 matter reported here. It will be self-evident that books often cited 

 will not have their full title given each time. Furthermore, I have not 

 cited all references that have been used, since that would have 

 lengthened the list unduly and have restricted myself mainly to sum- 

 marizations and to books. 



All measures and weights are given in the metric system, and other 

 data have been changed to this when necessary. Temperature is given 

 in degrees centigrade, and the designation "C." is usually omitted. 



R. Hesse 

 Bonn, late March, 1924 



