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 
horny lid. 
Sub-order 2. Ctenosto- 
mata.^f 
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; cells 
^ always calcareous. 
Sub-order 1. — Chilostomata. 
The Chilostomata, which contain many more species than all 
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 0. Escharina, in 
which the whole front wall is calcified. 
A and Bl. 
* EMos, outside ; proMos, vent. f Entos, inside ; proJctos, veni. 
X Gumnos, naked ; laimos, throat. § Phulassein, to guard ; laimos, throat.. 
|| Cheilos, lip ; stoma, mouth. % Ktenos, of a comb. 
** EuMos, circle. 
