PREFACE. 



' The publication of this book which was completed in 

 1918 has been greatly delayed. This is due partly to the 

 unfavourable times and partly to the doubts with which 

 every new theory is received. Thus, having presented it 

 first to the Royal Academy of Sciences of Amsterdam, 1 was 

 invited, after a year had elapsed, to ask for its return 

 since the commission which had to leport on it could not 

 come to unanimity Two of the three members refused to 

 share the opinion of the third, professor VAN Wyhe, 

 according to whom the present book ought to be confiscated 

 and consigned to the flames '). Finally, however, they 

 yielded to the implacability of the latter. Thus the excuse 

 of too high costs was advanced to help the three p.ofessors 

 out of this difficult position. 



All the more, therefore, do I feel under an obligation 

 to the „Koninklijke Natuurkundige Vereeniging" (Royal 

 Society of Natural Sciences) of Batavia for its confidence, 

 and for its permission to insert the article into the "Na- 

 tuurkundig Tijdschrift voor Nederlandsch Indie" and to 

 use the type for this present book. 



Having experienced how superficial sometimes the 

 judgment even of well reputed zoologists may be, I should 

 like to urge the reader not to set aside this book after 

 having read some ten pages, saying: "a stomodaeum be- 

 coming converted into a medullary tube .... nonsense". 



^) Professor Van Wyhe who is a supporter of the "trimerism" 

 theory was so indignant at the publication of this book that he even 

 refused at my request to give me the names of a few of his own 

 articles, for the completion of my literature list. Since in my present 

 residence I could not look them up, they are missing in the list, for 

 which I ask the readers indulgence. 



