PREFACE 



THE studies embodied in this work were begun by me in the year 1896, after I 

 had completed an essay on the Bryozoa in the Danish chalk-formation, 

 which received the paloeontological prize offered by the Royal Danish Society of 

 Sciences. During my investigations on the fossil species I obtained a strong im- 

 pression of the imperfect condition of the classification of the Bryozoa, as I was 

 frequently in doubt as to which genus or family I should refer a given species to, 

 and I became convinced of the necessity of making more detailed studies on the 

 recent Bryozoa before thinking of publJBhing a work on the numerous Bryozoa 

 from the Danish Chalk. I did not imagine, however, that this work would take 

 such a long time. 



In this work, which deals with the most difficult^ and at the present time 

 most numerous of the three orders of the Bryozoa, the Cheilostomata, I have made 

 an endeavour to reform the classification, and as basis for such a reform I have 

 first of all made a comparative' study of the structural features of most import- 

 ance in systematic regard. I have included all the families and most of the genera 

 of which I have been able to examine material and which I might consider as 

 well-founded. With regard to the species 1 have not followed the same procedure 

 everywhere ; in the case of some families and genera I have been content to name 

 a number of the species belonging to them, whilst in other cases I have described 

 more or fewer, partly new, partly older but not sufficiently investigated, inter- 

 esting species. Of the interesting genus Thalamoporella I have described all the 

 species I have had the opportunity to examine. The procedure I have followed 

 in the individual cases has in part been determined by my material; but I may 



' »Our real perplexities commence when we attempt to frame the families and genera; for In the 

 case of the Polyzoa it is extremely difficult to seize the significant characters. This remark applies 

 especially to the Cheilostomata.* Th. Hincks: British Marine Polyzoa, Introduction, pag. CXXVII. 



