POLYZOA. 



57 



With the exception of one genus (Loxosoma), all Polyzoa form 

 colonies, which arise by the continual budding of the cells, the buds 

 remaining attached to the parent cells. The colonies vary endlessly 

 in form and habit, occurring as crusts on rocks, etc., masses, broad 

 fronds, branching tree-like growths, bushy tufts, etc. 



The texture and consistency may be gelatinous, cartilaginous, 

 horny and flexible, or stony. 



The great majority of species are marine, but a considerable 

 number inhabit freshwater. The Polyzoa are classified as follows : — 



Group I. Ectoprocta.* 

 Vent opens outside 

 the circle of tenta- 

 cles. 



/ Order I. Gymnolse- 

 mata.J 

 Lophophore and tenta- 

 cular crown circular. 

 Without a lobe over 

 the mouth. 



Order II. Phylactolse- 

 mata.§ 

 Lophophore and tenta- 

 cular crown horse- 

 shoe shaped. With 

 lobe over the mouth. 

 Fresh water forms 



Group II. Entoprocta.f 



Vent opens inside circle of tentacles. 



Sub-order 1. Chilosto- 

 mata.|| 

 Orifice of cell with a 

 liorny lid. 



Sub-order 2. Ctenosto- 

 mata.^ 

 Orifice of cell closed 

 by a membranous 

 comb - like frill. 

 Always fleshy or 

 horny. 



Sub-order 3. Cyclosto- 

 mata.** 

 Without lid or frill; 

 orifice of cell usu- 

 ally circular; ceils 



\ always calcareous. 



Sul-order 1. — Chilostomata. 



The Chilostomata, which contain many more species than all Cases;; 

 the other groups put together, are divided into three sections : — ^ ^'^'^ -^ ^ ■ 

 A. Cellularina, in which the cells are more or less boat-shaped or 

 cornucopia-shaped, and joined together to form flexible branching 

 colonies ; B. Flustrina, in which the cells are typically shaped like 

 oblong boxes with membranous front walls ; and C. Escharina, in 

 which the whole front wall is calcified. 



* Elitos, outside ; froktos, vent. f Entos, inside ; proMos, vent. 



X Gumnos, naked ; laimos, throat. § Phulassein, to guard ; laimos, throat. 



1; Cheilos, lip ; stoma, mouth. T[ Ktenos, of a comb. 



** KuMos, circle. 



