Vin PREFACE 



great interest in my interpretations and ideas. I have, therefore, 

 now a welcome chance to answer all the critical observations 

 that have so far been made as regards my suggestions. 



The present volume must not be simply considered as a se- 

 cond revised edition of the first volume even if I deal in both 

 these books with the same or at least similar problems. This 

 book is a completely new work: the foundations only of the 

 two books have remained the same. 



To these few words of preface I wish to add a few more 

 words dictated by my feelings of indebtedness. Above all, I 

 wish to thank all those critics of my earlier studies who have 

 helped me to clarify many points that had previously been 

 not clear. They must excuse me if I have occasionally used too 

 vehement words that have been dictated "by the heat of the 

 struggle." My wish has alw^ays been to convince them. I can 

 not accept the suggestion made by a prominent scholar that 

 such revolutionary novelties have to w^ait the till present gen- 

 eration dies out and the next generation becomes convinced of 

 the correctness of the new concept. 



My special thanks go to my dear friend, Professor Dr. Otto 

 Steinbock (Innsbruck, Austria). He has not only critically read 

 my manuscript ;he has also always excelled as a noble colleague. 

 Without any previous knowledge of our researches, we both 

 came to the same conclusions regarding the origin of the 

 Eumetazoa. Each of us has made his researches in his special 

 group of animals: Professor Steinbock has mainly worked on 

 the Turbellaria, and I myself mainly on the Cnidaria. Otto 

 Steinbock came to the conclusion that the Turbellaria, i.e. the 

 acoelous Turbellaria, must be the most primitive Eumetazoa, 

 even before I was able to formulate the results of my studies. 

 As a consequence of this discovery, Steinbock had correctly 

 made important conclusions especially as regards the way the 

 Eumetazoa had evolved, and as regards the previously firmly 

 held theory of the germ layers. He did not, however, succeed 

 in publishing the results of his research and his ideas. Just 

 before the outbreak of the Second World War, Steinbock gave 



