XU INTRODUCTION 



whether certain flora and fauna elements on both sides of the Ocean reached 

 their present areas by dispersal over the existing lands of the continents and 

 subsequently became extinct in interior parts of these lands where they do 

 not appear today, as maintained by some biogeographers, or, whether these 

 continents in a not too remote past were in direct contact with each other; 

 furthermore, in case such a contact existed, whether they might have been 

 united by land-bridges that have later mysteriously disappeared or by a 

 continuity that has been subsequently broken by some kind of a displace- 

 ment? 



In recent years so many new facts have been brought into hght regarding 

 the old problem of the history of the North Atlantic biota that a fresh attack 

 on their problems seems almost overdue. It also seems as if we were nearing 

 the stage when the geological information permits us to construct a somewhat 

 better timetable for possible dispersal periods. Even the biological facts and 

 methods concerning studies of the evolution of the biota themselves have 

 increased and improved so that we now are able to evaluate their true 

 relationships better and attack many of the problems experimentally. 



Since the problems of the history of the North Atlantic biota cannot easily 

 be understood by studying the continental conditions alone, it seemed 

 advisible to search for a concrete foundation of the discussion and to restrict 

 this broad subject in space and time. This is one of the reasons that we held 

 this first symposium in Iceland, since this automatically concentrates the 

 discussions to studies of the present conditions in light of our knowledge of 

 the Pleistocene and the Tertiary. Not only is this island a "stepping stone" 

 between the continents, but it may in itself harbor such data that are the key 

 to the solution of many of the problems to be considered. 



This symposium was organized to clarify what are the facts, or to permit 

 the presentation of available evidence on certain phases of an important 

 scientific problem. It is meant as an opportunity to state in one issue what has 

 been gathered and to gain new insights and outlooks from different fields of 

 science. It is, however, not meant to prove a certain theory or to disprove 

 another. A scientist's aim in a discussion with his colleagues is not to persuade 

 but to clarify. It is the hope of the organizers and sponsor of this meeting that 

 we will leave it better informed than we came, ready to reconstruct and 

 construct anew on the foundations laid down here. 



