THE INFUSORIA. 



153 



length and ^-Joth in breadth. They inhabit both fresh and 

 salt water, and some have sheaths and some not. . 



The Infusoria are likewise furnished with cilia, by 

 means of which they move and bring their food within 

 reach, and having mouths, are superior to the Foraminifera 

 and other Protozoa, or lowest forms of animal life, which 

 can hardly be said to 

 have any organs, and 

 absorb their food 

 through the whole sur- 

 face of their bodies, 

 which are but specks of 

 slime or jelly. 



Many of the Infu- 

 soria are covered by a 

 sheath or shell, and 

 most commonly in- 

 crease by the simple 

 process of splitting 

 themselves in two. 



They multiply so rapidly that one (Polygastria) may in 

 forty- eight hours have given rise to a progeny too large .to 

 be expressed in numbers. 



Below the Infusoria, are the Polycystinae, or Radiolaria, 

 which are nearly allied to the Foraminifera, but have shells 

 of flint often set all over with hair-like needles, the whole 

 shell, needles and all, being a mere speck of the size of 

 a grain of sand. (Fig. 33.) Some are extremely beautiful 

 objects when magnified, and resemble the carved ivory balls 

 for which the Chinese are noted. Notwithstanding their 



33. SKELETON OF RADIOLARIAN. 



