VAIUOUS INVERTEBRATE ANIMALS. 109 



II. SPECIAL. 



Protozoa. 



Foraminifera. — 'i'he dead shells occar 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 diied, and the 

 rougher material separated by a sieve or net. The finer portion is 

 put into a bowl of water, and stirred up. The more 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. 



Eadiolaria. — 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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