486 



PROTOZOA. 



The name Protozoa comes from the Greek protos, first, 

 in the sense of simplest, and soon, an animal. 



FIG. 733. 



Portion of Sphcerozoum, more 

 Protozoans. highly magnified, 



a, SphcBrozoum ; b, Gregarina ; c, Amoeba ; all magnified. 



The Protozoans are probably more numerous than all 

 other animals of the globe. They abound in every ditch 

 and pool, every stream, pond, and lake, and in almost 



FIG. 734. 



Protozoans around an aquattc plant a leaf of Duckweed. See page 9. 



every part of the ocean. And there is hardly a drop of 

 water that is not inhabited by some of them. They were 

 also abundant in the past geologic ages. Their skeletons 

 or hard parts abound in the rocks in many places ; and in 

 some countries rocky strata hundreds of feet in thickness 



