rns EiiizoFODS. 9 



food; (4) chemical changes in the food take place: in other 

 words, it digests its food, i.e., separates or secretes tlie por- 

 tion necessary to nourish its body from those portions whicli 

 it rejects as waste; (5) it may also be said to breathe, the 

 changes involved in talcing food, especially oxygen, caus- 

 ing the production and excretion of carbonic acid; (6) and 

 finally, it can reproduce its kind. Thus we have foreshad- 

 owed in this exceedingly simple organism all the important 

 functions of animal life. 



Classes of Protozoa. 



1. Body formless, usually shelled WUzopoda. 



2. Body cylindrical ; parasilic Oregarinida. 



3. Body ciliated Infusoria. 



Class I. — Ehizopoda {Root-animalcules). 



General Characters of Rhizopods. — Besides the Ammba, 

 which is a representative of tliJs class, there arc a uumbei 



Fig. 4. — A Foraminifer. Glohigerina hulloides, magnified 70 diameters. 



of fresh-water forms which have simple, sillcious 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 the animal protrudes 

 its false feet or pseudopods. These shelled Ehizopods are 



