PHYLUM POLYZOA 



Classes 



1. Ectoprocta 



Orders 

 1. Phylactolaema. 



.2. Gymnolaema... 



Sub-Orders 



'1. Cyclostomata. 



2. Trepostomata. 



3. Cryptostomata. 



4. Cheilostomata. 



5. Ctenostomata. 



2. Entoprocta. 



With the exception of the genus Loxosoma all the 

 Polyzoa 1 are colonial animals, numerous individuals living 

 in association. The colony is nearly always fixed, and may 

 be arborescent, laminar, almost massive, or encrusting 

 shells, stones, or plants. The entire colony is known as 

 the zoarium; each individual (fig. 89 A) has a sac-like 

 form ; at the upper end there is a platform or disc, the 

 lophophore, on which tentacles (t) are placed, arranged 

 either in a circle or in the form of a horse-shoe. In most 

 forms the tentacles are not contractile, but are provided 

 with cilia, which produce a current of water that conveys 

 food to the mouth (o). The anal aperture (a) is near the 

 mouth, generally below the lophophore, but in some forms 

 within the circle of tentacles. On account of this approxi- 

 mation of the mouth and anus the alimentary canal is 

 bent into a U-shape; in it may be distinguished oesophagus 

 (oes), stomach (st), and intestine (int). Between the ali- 



1 The name Bryozoa is used for this Phylum by many authors. 



