THE AMCEBA AND OTHER ROOT-ANIMALCULES. 15 



especially oxygen, causing the production and excretion of 

 carbonic acid; (6) and finally, it can reproduce its kind. 

 Thus we have foreshadowed in this exceedingly simple 

 being all the important functions of animal life. Besides 

 the Amoeba, which is a representative of this class, there 

 are a number of fresh-water forms which are protected by 

 simple, silicious shells; but in the sea there are thousands 

 of species whose shells are partitioned into chambers, and 

 are usually perforated with holes like a sieve, through which 



FIG. 9. A Foraminifer. Globigerina, magnified 70 diameters. 



the animal protrudes its false feet or pseudopods. These 

 shelled Rhizopocls are called Foraminifera (Latin, foramen, 

 a hole or aperture ;/enw.<?, bearing. Figs. 9 and 10). They 

 have the same power as snails and clams to separate or 

 secrete from the sea-water the lime or silica dissolved in it, 

 and to build up a shapely, graceful, and strong shell; while 

 others gather with their finger-like processes grains of sand 

 or bits of shell and form them into houses of stone-work. 

 Many Foraminifera float in calm weather on the surface of 

 the sea, and when they die their shells slowly sink to the 

 bottom. They are exceedingly abundant, and the shells at 

 the bottom accumulate in such quantities as to make a gray 



