432 



EVOLUTION OF ANIMALS 



Part V 



There are five classes of protozoans: 



1 . Mastigophora, or flagellates, with one or more flagella. 



2. Sarcodina or rhizopods, with pseudopodia. 



3. Sporozoa, with no locomotor structures. 



4. Ciliata, or ciliatcs, with cilia throughout life. 



5. Suctoria, with cilia in the young and tentacles in the adult stages. 



Class Mastigophora or Flagellata 



This class includes both the plantlike phytoflagellates that contain chromo- 

 plasts with chlorophyll and often other pigment, and the zooflagellates that 

 are clearly animals and without chlorophyll. The phytoflagellates make their 

 food from inorganic matter and are basically constructive organisms in what- 

 ever community they live. The zooflagellates take their food from plants and 

 other animals. 



Phytoflagellates 



Structure. The brilliantly colored euglenas of several species are common in 

 fresh waters (Fig. 21.6). Among their characteristic structures are the green 



flagellum 



reservorr 

 or gullet 



poramylum 



body 



(starch) 



pellicle 



eye spot 



ractile 

 cuole 



oroplast 



cleus 



Fig. 21.6. Euglena, a fish-shaped green 

 protozoan that lives in many stagnant pools 

 of fresh water. It is just visible to the naked 

 eye but the millions of them often turn the 

 surface of a pool brilliant green. There are 

 many species, in some the mouth leads to a 

 gullet as in this one, others are without these 

 structures, and probably make all of their 

 food by photosynthesis. The flagellum, a 

 bundle of contractile fibrils bound together 

 in a sheath, is an efficient swimming organ. 

 There are many species of Euglena, in some 

 the body is long and slender. 



chloroplasts, (disks, ovals, stars, or bands) scattered through the body and 

 about the central nucleus. The flagellum that arises from a minute body 

 (blepharoplast) in the side of the cytopharynx is associated with the control 



