INTRODUCTION 



form, the life and the distribution of plants and animals, for 

 his theory. 



ISTo matter. In any case, since the publication of my 

 papers various theories concerning evolution have appeared, 

 whose authors have not troubled themselves in the least about 

 the facts established by me, have not even mentioned them, 

 although they contradicted their theories. But I will not go 

 so far as to say with Nageli that this was " because they were 

 unable to use these facts." In an address to the second 

 general meetmg of the Congress of German Naturalists and 

 Physicians at Freiburg i.B., which is printed as an appen- 

 dix to this book, I had developed a theory based on facts. 

 Subsequently, in various articles in the Zoologisclier Anzeiger, 

 and in the journal Humholdt, as well as in a lecture on the 

 markings of birds and mammals^ delivered as early as 1882, 

 which was afterwards published, and which is reproduced in 

 the present book, I largely added to the number of these 

 facts, and brought forward further irrefragable evidence for 

 my views. But notwithstanding all this, not one of those 

 who have set up theories or hypotheses of their own in our 

 subject took any notice of my facts. 



As we shall see, I have no special reason to complain in 

 this matter. What has happened to me has happened to 

 others. The botanist Nageli makes, as I mentioned, the 

 charge against such writers that they have not referred to 

 the facts brought forward by him because they could not 

 make use of them. 



I might express myself in milder terms thus : The founders 

 of theories of evolution set up since Darwin's time have as a 

 rule deviated from Darwin's path, inasmuch as they have 

 sought to adapt the facts to their ideas and opinions, instead 



^ Ueher die Zeichnung dec Vogel und Sdugethiere. Lecture delivered at the 

 Meeting of the " Verein filr Vaterlandische Naturkunde in Wiirttemberg " at Nagold 

 on 24th June 1882. Wllrttevibergischenaturwissenschaftliche Jahreshefte, 1883. 



