THE miZOPODB. 
food; (4) chemical changes in the food take place: m other 
words, it digests its food, i.e., separates or secretes the por- 
tion necessary to nourish its body from those portions which 
it rejects as waste; (5) it may also be said to breathe, the 
changes involved in taking food, especially oxygen, caus- 
ing the production and excretion of catbonic 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. 
Class I. — Rhizopoda {Root-animalcules). 
General Characters of RMzopods. — Besides the Amceha, 
which is a representative of this class, there arp a numbei 
Fig. 4.— a Foraminifer. Globigerina bulloides, magnified TO diameters. 
of fresh-water forms which have 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 the animal protrudes 
its false feet or pseudopods. These shelled Ehizopods are 
Classes of Protozoa. 
1. Body formless, usually shelled 
2. Body cylindrical; parasilic 
3. Body ciliated , 
Rhizopoda. 
Gregarinida. 
Infusoria. 
