84 HANDBOOK OF PROTOZOOLOGY 



The class Mastigophora includes free-living as well as para- 

 sitic forms. Its members are found in fresh and salt waters of 

 much wider range than are other groups, because of their holo- 

 phytic nutrition. Many are free-swimming, others creep over 

 the surface of submerged objects, and still others are sessile. 

 Together with the algae, the Mastigophora compose a major 

 portion of plankton life, which is the basis for the existence of 

 all higher forms of aquatic animals. The parasitic forms are 

 ectoparasitic or endoparasitic. The latter live either in the di- 

 gestive tract or in the circulatory system of the host. Trypan- 

 osoma, a representative genus of the latter type, includes impor- 

 tant disease-causing parasites of man and of domestic animals 



According to Doflein, the Mastigophora are divided into two 

 subclasses: Phytomastigina and Zoomastigina. 



SUBCLASS I PHYTOMASTIGINA DOFLEIN 



Most of the Phytomastigina possess chromatophores, and 

 their usual method of nutrition is therefore holophytic, though 

 a few are mixotrophic. The majority are conspicuously colored. 

 vSome that lack chromatophores are included in this group, 

 since their morphology and development resemble closely those 

 of typical Phytomastigina. According to Calkins, the subclass 

 is divided into six orders, as follows: 



With cellulose shell composed of plates; two flagella, one of which is 



transverse Order 3 Dinoflagellida 



Without cellulose shell composed of plates; no transverse flagellum 

 Chromatophores yellow or brown; contractile vacuoles simple 



Cytopharynx absent; body not flattened Order 1 Chrysomonadida 



Cytopharynx present; body flattened Order 2 Cryptomonadida 



Chromatophores green; contractile vacuoles simple or complex 



Without cytopharynx; vacuole simple Order 4 Phytomonadida 



With cytopharynx; vacuole complex 



Metabolic products paramylum Order 5 Euglenoidida 



Metabolic products oil Order 6 Chloromonadida 



ORDER I CHRYSOMONADIDA STEIN 



Most of the Chrysomonadida are minute. They show vari- 

 ous body organizations. Chromatophores are yellow to brown 



