THE SARCODIXA 



155 



sented on the one hand by species that are animal-like, the Zoomas- 

 tigina, and on the other by plant-Hke types, the Phytomastigina. 

 Mastigophora means "whip-bearers." 



Class Infusoria. — This class consists of forms in which the cell 

 has cilia during the whole or a part of the life cycle (Fig. 84 C and 

 D) . With few exceptions, the nuclear material is represented by a 

 larger "vegetative" macronucleus, and a smaller, "generative" 

 micronucleus (Fig. 95 E). The infusoria include many highly 

 specialized protozoa. They were so named because many species 

 of this class are often abundant in " infusions." 



Phaous 



Peranema 



Sphaerella 



Ceroomonas 



Monoaiga 



Fig. 85. — Pi,epre.sentative Sarcodina (upper row) and Mastigophora (lower 



row.) 



Mastigamceba, which has a flagellum and pseudopodia, is classified as a mastigophoran. 



(Drawn by C. W. Wilson.) 



Class Sporozoa. — These are parasitic forms in which the cell 

 often shows marked degeneration in the locomotor and other 

 structures necessary for free life (Fig. 84 E). Spores or seed-like 

 encysted stages give the group its name, "seed anmials." 



The Sarcodina 



Structure of Amceba. — The class Sarcodina includes the sim- 

 plest forms that are found among Protozoa, although there are 



