CHAPTER XVII 



POLYZOA 



INTRODUCTION GENERAL CHARACTERS AND TERMINOLOGY BROWN 



BODIES HISTORY OUTLINES OF CLASSIFICATION MARINE 



POLYZOA OCCURRENCE FORMS OF COLONY AND OF ZOOECIA 



OVICELLS AV1CULARIA VIBRACULA ENTOPROCTA. 



THE following pages 1 deal with animals whose very existence is 

 hardly known to those who are not professed naturalists. There 

 are but few Polyzoa which have earned the distinction of possess- 

 ing a popular name, and most of such names as do exist cannot 

 be found outside treatises on Natural History. It is true that 

 many of the members of this group have been vaguely termed 

 " Zoophytes " ; but this term implies no more than that they 

 possess a superficial resemblance to certain plants, and it must 

 be remembered that this habit of growth is assumed by many 

 animals which have nothing to do with the Polyzoa. The term 

 " Coralline " is sometimes applied to those calcareous Polyzoa 

 which grow into coral-like forms ; and the Tertiary deposit 

 known as the " Coralline Crag " is so called from the large 

 number of fossil Polyzoa which it contains. 



The Polyzoa are none the less a most attractive group. Let 

 any one examine a dry piece of a brown paper-like substance 

 (Fig. 232, A), which may be found thrown up on the beach on 

 many parts of our coasts. Of this species (Flustra foliacea'), the 



1 The account given in the following pages lias been deliberately restricted, for 

 the most part, to British species. Our own fauna contains an assemblage or 

 1'oly/oa which is so representative that it has seemed better to do some justice to 

 the British forms than to attempt to cover the whole ground in the limited 

 number of pages devoted to this group. Those who desire to make a wider study 

 of the subject should refer, for marine forms, to Busk's Cataloyuc of Marine 

 VOL. II 2 H 



