MIMOSELLA. : at7 
From a creeping fibre, which spreads over the surface of 
Fuci, rise graceful, tapering stems, pinnate, much attenuated 
towards their extremities, and running out into filamentary, 
tendril-like prolongations. These stems are commonly from 
an inch to an inch and a half in height. They are jointed 
at intervals; and immediately below each joint spring two 
opposite pinnee, also jointed, tapering, and slightly curved. 
“The pairs of pinne do not all lie in the same plane. 
Along these are set the cells, which are ovate, elongate, 
biserial, and opposite. ach cell is attached to a small 
prominence on the side of the pinna, which is perforated. 
A circular orifice on one side of the cell near the base fits 
over this, and a joint is thus secured, by means of which 
the polype can move its dwelling forward in one direction 
and back again. This is frequently done. The polypes 
are continually swaying their cells to and fro; sometimes 
_ all the cells on the pinna are folded together on the upper 
side, just as the leaflets close on the leaf of the sensitive- 
plant (Mimosa), and hence the generic name. Towards 
the base of each pinna the cells are long and oval; as they 
approach the apex they became short and globose, and at 
last are little more than little round excrescences. 
‘The polypes have eight arms, and are furnished with a 
