VARIOUS INVERTEBRATE ANIMALS. 
109 
II. SPECIAL. 
Protozoa. 
Foraminifera .—The dead shells occur in shelly sands, which are 
sometimes very rich in them. The living organisms are found in 
the mud or sand of the sea-bottom, or adhering to sea-weeds. 
Some species of Foraminifera are pelagic, and live at the surface 
of the ocean in warm temperate and tropical waters; these can be 
collected in the towing-net, or, better, into vessels of sea-water, as 
several species possess delicate spines liable to be broken in a net. 
To separate Foraminifera from sand or mud, when the shells alone 
are required, Professor W. 0. Williamson’s method may be adopted. 
The sand or mud dredged from a few fathoms is dried, and the 
rougher material separated by a sieve or net. The finer portion is 
put into a bowl of water, and stirred up. The moi'e delicate shells 
with their chambers full of air will float, and can be skimmed off and 
put into another bowl of water; the water is drawn off with a 
siphon, and the residue is dried. It is better, before drying the 
residue, to heat it with caustic potash, and again wash in water. 
To obtain living Foraminifera, the specimens can be picked off 
from corallines and other sea-weeds ; or the mud and fine sand that 
come up in the dredge are put into vessels of water, and stirred : the 
shells, full of protoplasm, will sink. 
Mr. J. J. Lister uses a horse-hair sieve, with bolting-cloth fastened 
beneath, to obtain certain shallow-water species. The sieve is placed 
in a suitable pool of sea-water, and handfuls of sea-weed are well 
shaken in the water over the sieve. The bolting-cloth catches the 
Foraminifera which pass through the sieve. The specimens are 
killed by putting them in a mixture of warm saturated solution of 
corrosive sublimate (4 parts) and glacial acetic acid (1 part) ; they 
are then cleaned in water, and finally put into picrocarmine for 
some hours. 
Radiolwria .—Many species live at and near the surface, where 
they sometimes occur in great abundance. They may be captured 
with a towing-net or in vessels of sea-water. 
Some are without a skeleton, and appear like minute oval or 
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