378 HISTORY OF BRITISH ZOOPHYTES. 
gizzard. They are very vigorous in their movements. It 
is very interesting to watch the little creatures manceuvring 
their cells. Every now and then, as if some common 
impulse stirred them, all the polypes on a single pinna 
will move forward their cells, and the frond close like the 
Mimosa-leaf when touched. More commonly they are in- 
dependent in their movements. A single cell here and 
there will be seen in motion, while the rest remain quiet. 
“The mouth of the cell is furnished with the charac- 
teristic setze of the family. When the cells are detached, 
the circular opening near the base may easily be detected.” 
(Hincks.) 
Il. POLYZOA HYPPOCREPTA. 
The following is Professor Allman’s arrangement of the 
genera :— 
Polype-mass floating. CrisTaTELLIDs. 
One genus only—CrisTaTEeLLa. 
Polype-mass rooted. 
+ Massive or confervoid, inarticulate. PLumatTELuips. 
Massive and sponge-like. ALCYONELLA. 
Confervoid, tentacular disc crescentic. PLUMATELLA. 
