CHAPTEE XVI. 

 THE LOWEST ANIMALS, Subkingdom PROTOZOA. 



Characteristics. 



THE lowest animals belong to a .world invisible to the naked eye, 

 a world whose very existence was unknown two hundred years ago, 

 despite the fact that its inhabitants abound on every side. In 1755 Rosel von 

 Rosenhof saw sticking on the side of a glass vessel of water and weed a tiny 

 particle of jelly, the movements of which attracted his attention. " It fastened 

 itself," he writes, "on the side of the glass; and since, like animals, it moves, 

 although very slowly, from place to place, and thereby continually alters its form, 

 and as I frequently examined the water with a magnifying-glass, the creature was 

 necessarily discovered ; as soon as I touched it, it contracted itself into a sphere and 



PROTEUS ANIMALCULE. 



The same animal in different shapes. (Magnified 600 diameters.) 



fell to the bottom." Rosel removed the specimen to a watch-glass, and observed it 

 continually changing its shape. In consequence of this peculiarity, he named the 

 animal " the small Proteus " after the monster of fable. Later the animal was named 

 Amoeba, as the name Proteus had been bestowed on another animal. An amoeba is 

 composed of a small particle of living substance, called protoplasm, and resembles a 

 tiny blob of jelly, which continually but slowly changes its shape. The amoeba is 



