PREFACE. 



In presenting a second "instalment of the translation of the 

 Lehrhuch der vergleichenden EntvjicklungsgescMchtc der ivir- 

 belloseii TJiierc to students of Zoology, I feel that an apology 

 is due to them for the long interval of time that has elapsed 

 since the appearance of the first part. Professors Mark and 

 Woodworth, the translators of Vol. I., found themselves 

 unable to spare time to continue the translation, and others 

 who subsequently undertook the work were for similar reasons 

 obliged to relinquish it. Consequently the book came into 

 the hands of the present translator and editor only last year ; 

 and although we have endeavoured to push the work forward 

 as quickly as possible, the task of translating, printing, and 

 editing has necessarily consumed a considerable time. The 

 whole work, however, is now well in hand, and, in issuing 

 Vol. II., we can confidently hope that no long period will 

 elapse before the production of Vols. III. and IV., the former 

 being already in the press. 



It will be noticed that the order of the subject-matter has 

 been changed. In its original form the Text-book is divided 

 into three parts of unequal size. That already translated 

 (Part I.) is much smaller than either of the remaining parts. 

 We have consequently found it necessary to divide the second 

 and third parts of the original into three. In doing so we 

 were faced by a difficulty. If the original sequence of the 

 chapters was to be retained, each part could not be made 

 complete in itself unless the relative size of the volumes was 

 left out of consideration. It was therefore thought preferable 

 to alter slightly the original sequence of the chapters. Those 

 dealing with the Phoronidea, the Bryozoa Ectoprocta and 



